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Tuesday, 28 August 2018
Time Speaker Title Resources
16:00 to 17:00 Daan Frenkel O​rder, disorder and entropy (Infosys-ICTS Chandrasekhar - Lecture 1)

Since the middle of the twentieth century, the traditional picture of entropy as a measure of disorder has shifted. However, this development is not well known outside the Statistical Mechanics community. In my talk, I will discuss example s where entropy increases with increasing order, I will briefly touch on Gibbs’ paradox and I will discuss how recently developed numerical tools allow us to compute close and distant relatives of Boltzmann’s entropy.

Wednesday, 29 August 2018
Time Speaker Title Resources
09:00 to 09:45 Marjolein Dijkrsta Predicting and designing the self-assembly of colloidal particles: a computer game
09:45 to 10:30 Jose Maria Tavares Phase diagrams of self assembly patchy particles

Patchy particles are hard cores decorated with dis- crete attractive sites (patches) on their surfaces and are used as models for systems with strongly anisotropic interactions. The bonding of particles through their patches promotes the formation of large self-assembled aggregates. The interaction between two patches is specified by an energetic parameter and by the volume available for the bond (bonding volume), that sets the loss of (translational) entropy when a bond is formed [1].

Numerical simulations and theoretical calculations of the phase diagram of one-component patchy parti- cle fluids have revealed that lowering the number of patches (or valence M) depresses the critical proper- ties (critical temperature, critical density, and criti- cal pressure). Because the two-phase region shrinks, the density of the coexisting liquid also decreases with M, opening up the possibility of low density equilib- rium liquid states (empty liquids) that nevertheless have a percolated structure (network fluids). This effect is limited by the lowest possible value of the valence for which both percolation and phase sepa- ration can be found, M = 3 [2]. To overcome this limitation, we have proposed and studied two families of patchy particle models, that are expected to show an effective valence M < 3: (i) a single component system with particles that have 2 patches of type A and n patches of type B that form AA and AB bonds only (2AnB model) [3, 4] and (ii) binary mixtures, where each specie has a different number of patches and similar or dissimilar patches [5]. In this talk, I will present some of the striking results obtained for the liquid vapour phase diagrams of these models us- ing Wertheim’s theory (in most cases confirmed by Monte Carlo simulations) [1].

The phase diagram of the 2AnB model exhibits a reentrant liquid binodal (see Fig. 1), that leads to the appearance of equilibrium liquid states of arbi- trarily low densities [3, 6]. It can be shown that this reentrance is originated by the competition between two types of entropic defects that perturb the ground state. In some extreme cases, when the entropy of AB bonds is much larger than that of AA [4] or when rings of AA bonds are present [7], a closed liquid vapor coexistence region with an upper and a lower critical point is obtained.

The phase diagrams of binary mixtures of patchy par- ticles with different valences (M1 and M2) and a single energy scale (i.e., all patches identical) have a strong dependence on M1 and M2, originated by the compe- tition between the entropy of bonding and the entropy of mixing. The calculation of the critical properties of these mixtures reveals that the empty fluid regime is only obtained for (M1, M2) = (2, 3) and that, for gen- eral mixtures, the role of the entropy of mixing in de- termining the critical properties can only be neglected when M2 − M1 = 1 [5].

Corresponding author: jmtavares@fc.ul.pt

  1. P.I.C. Teixeira, and J.M. Tavares, Curr. Opin. Colloid Interface Sci. 30, 16 (2017).
  2. E. Bianchi, J. Largo, P. Tartaglia, E. Zaccarelli, and F. Sciortino, Phys. Rev. Lett. 97, 168301 (2006).
  3. J. Russo, J.M. Tavares, P.I.C. Teixeira, M.M. Telo da Gama, and F. Sciortino, Phys. Rev. Lett. 106, 085703 (2011).
  4. N.G. Almarza, J.M. Tavares, E.G. Noya, and M.M. Telo da Gama, J. Chem. Phys. 137, 244902 (2012)
  5. D. de las Heras, J.M. Tavares, and M.M. Telo da Gama, Soft Matter 7, 5615 (2011).
  6. J.M. Tavares, and P.I.C. Teixeira, Phys. Rev. E 95, 012612 (2017).
  7. L. Rovigatti, J.M. Tavares and F. Sciortino, Phys. Rev. Lett. 111, 168302 (2013).
10:30 to 10:55 -- Coffee Break
10:55 to 11:40 G. V. Pavan Kumar Plasmon-Activated Colloidal Assembly : Chains and Networks

Light activated, assembly, movement and pattern for- mation of soft-matter has been studied in the context of micro- and nano-robots in fluidic environments. These processes have also gained interest in the con- text of light-activated dynamic networks that can be controlled in space and time, which further serves as interesting experimental models to study driven ac- tive matter and emergence phenomena. To this end, a variety of surface optical effects have been explored that can effectively interface soft-matter with confined optical fields.

One such optical process is excitation of surface plas- mon polaritons (SPPs). Interaction of visible light with thin-films and nanostructures made of coinage metals, such as gold and silver, can be used to excite SPPs at metal-dielectric interface. These surface elec- tromagnetic waves not only confine electric fields at sub-wavelength scale, but also facilitate thermal field gradients due to ohmic heating. In an essence, SPPs provide optical and thermal fields at metal-fluid in- terface, which can be controlled by an external laser beam.

We have been interested in interaction of soft-matter with SPPs at metal-fluid interface [1, 2]. Specifically, we have been interested in questions such as: how colloidal meso- and nano-structures behave in thermo- optical fields of SPPs? How will their assembly and dynamics alter when the dimensions of metal struc- ture change? What kind of unconventional patterns emerge due to interaction of SPPs with complex flu- ids?

In this presentation, we will introduce some relevant opto-thermal effects of SPPs and discuss how they can be harnessed to study assembly, dynamics and pattern formation of soft-matter at metal-fluid interface. Par- ticularly, we will discuss about formation of colloidal chains and networks in multiple plasmofluidic fields. We will conclude by discussing some new prospects of nanowire plasmons [3] that can confine and move colloids in a quasi-one dimensional channel.

This work was partially funded by DST Nanomission, India and AFRL, USA

Corresponding author:  pavan@iiserpune.ac.in

  1. Partha P. Patra, Rohit Chikkaraddy, Ravi P.N. Tri- pathi, Arindam Dasgupta, G.V. Pavan Kumar, Nature Communications 5, 4357 (2014).
  2. Partha Pratim Patra, Rohit Cikkaraddy, Sreeja Thampi, Ravi P.N. Tripathi, G. V. Pavan Kumar, Faraday Discussion 186, 95 (2016).
  3. Adarsh B. Vasista, Harshvardhan Jog, Tal Heilpern, M.E. Sykes, Sunny Tiwari, Deepak K. Sharma, Shailendra K. Chaubey, G.P. Wiederrecht, S.K. Gray, G.V.Pavan Kumar, Nano Letters 18, 650-655 (2018).
11:40 to 12:25 Prerna Sharma Self assembly of cyclic polygon shaped fluid membranes through pinning

2D liquid monolayer membranes of aligned rod like particles form in presence of depletion attraction in- duced by non-adsorbing polymer coils [1]. Surface ten- sion drives these monolayers to be circular in shape with edge fluctuations controlled by the chirality of the constituent rods [2]. Surprisingly, we find that fluid membranes assembled form mixtures of long and short rods are cyclic polygonal in shape with short rods forming the outer lobes and longer rods forming the inner faceted core of the polygon. We show that the origin of this anisotropic shape of membranes lies in the phenomenon of how one liquid spreads over an- other in presence of pinning sites. We outline the nec-essary and sufficient constraints on the nature of rods to obtain the stable out of equilibrium cyclic poly- gon membranes. Our results show the unique counter- intuitive scenario where disorder lead to self assembly of ordered structures.

We would like to acknowledge IISc, ISRO-STC and SERB-DST for funding this work.

Corresponding author:  prerna@iisc.ac.in

  1. Edward Barry, and Zvonimir Dogic, Proceedings of the National Academy of Sciences 107, 10348 (2010).
  2. T. Gibaud et al., Nature 481, 348 (2012).
12:25 to 12:45 Sujata Tarafdar Hierarchical self-assembly of desiccation crack patterns in clay induced by a uniform electric field

Crack patterns formed by desiccation in clay are known to give rise to characteristic patterns [1, 2]. The patterns are affected by various factors, such as the drying material, the substrate and ambient condi- tions like temperature and relative humidity. External conditions like electric fields and magnetic fields also control details of the crack patterns.

Cylindrically symmetric static DC (i.e. Direct Cur- rent) electric fields [3] and AC (Alternating Current) fields [4] can be used to tailor the crack patterns in specific geometrical arrangements. Here we describe another experiment.

We applied a uniform static electric field to an aque- ous layer of clay suspension while drying. This caused a self-assembly of the cracks into an interesting pat- tern, dictated by the energy supplied to the system.

Initially closely spaced straight cracks appear at the positive electrode. As the sample dries these cracks merge together in small groups. Several stages of this merging produces the final hierarchical pattern.

The final pattern is distinctly tree-like, or river like, consisting of hierarchical structures as shown in Fig. 1. River like crack structures have been observed and discussed previously [5], but not in dried clay pastes as we observe here. We try to analyse the patterns and explain their origin. The redistribution of mobile ions in the aqueous clay slurry is assumed to be responsible for the pattern formation. The process may be useful in producing tailored crack patterns for applications in nano-patterning.

We sincerely thank Tajkera Khatun and Sudeshna Sir- car for participating in this work and for offering valu- able suggestions.

Corresponding author:  sujata.tarafdar@gmail.com

  1. L. Goehring, A. Nakahara, T. Dutta, S. Kitsunezaki and S. Tarafdar Desiccation Cracks and their Patterns (Wiley VCH, Weinheim, Germany 2015).
  2. J. Allen, Philos. Trans. R. Soc. Ser B 315, 127 (1987).
  3. T. Khatun, M. Dutta Choudhury, T. Dutta and S. Tarafdar, Phys. Rev. E 86, 016114 (2012).
  4. S. Sircar, S. Tarafdar and T. Dutta, Appl. Clay Science, 156, 69 (2018).
  5. D. Hull, Fractography: Observing, Measuring and In-terpreting Fracture Surface Topography (Cambridge University Press, Cambridge 1999).
12:45 to 14:15 -- Lunch
14:15 to 15:00 W. Benjamin Rogers Using entropy to program self-assembly of DNA-coated colloids

DNA is not just the stuff of our genetic code; it is also a means to build new materials [1]. For instance, grafting DNA onto small particles can, in principle, ‘program’ the particles with information that tells them exactly how to put themselves together—they ‘self-assemble.’ Recent advances in our understand- ing of how this information is compiled into specific interparticle forces have enabled the assembly of in- teresting crystal phases [2], and could be extended to the assembly of prescribed, nonperiodic structures [3]. However, structure is just one piece of the puzzle; in actuality, self-assembly describes a transition between a disordered state and an ordered state, or a pathway on a phase diagram.

In this talk, I will present experiments showing that the information stored in DNA sequences can be used to design the entire assembly pathway. Using free DNA strands that either induce or compete with bind- ing between particles, I will show that it is possible to create suspensions with new types of phase behav- ior [4], enabled by our control of the entropy of the free strands [5]. I will also discuss preliminary ex- periments showing that we can measure directly the dynamics of transitions between different phases, us- ing a combination of techniques from droplet-based microfluidics, video microscopy, and image analysis. Going forward, this work could prove especially use- ful in nanomaterials research, where a central goal is to manufacture functional materials by growing them directly from solution.

We would like to acknowledge support from the Na- tional Science Foundation (NSF DMR-1710112).

Corresponding author: wrogers@brandeis.edu.edu

  1. W.B. Rogers, W.M. Shih, V.N. Manoharan, Nature Reviews Materials 1, 16008 (2016).
  2. Y. Wang, Y. Wang, X. Zheng, E. Ducrot, J.S. Yodh, M. Weck, D.J. Pine, Nature Comm. 6, 7253 (2015).
  3. Z. Zeravcic, V.N. Manoharan, M.P. Brenner, PNAS 111, 15918-15923 (2014).
  4. W.B. Rogers, V.N. Manoharan, Science 347, 639-642 (2015).
  5. J. Lowensohn, B. Oyarzun, G. Narvaez Paliza, B.M.Mognetti, W.B. Rogers, preprint.
15:00 to 15:20 Debasish Chaudhuri Confinement and crowding sets morphology and position of bacterial chromosome

To explain experimental results showing shape, size and dynamics of E.coli chromosomes in growing cells, we consider a polymer model consisting of a circular backbone to which side-loops are attached, confined to a cylindrical cell [1, 2]. Such a model chromosome spon- taneously adopts a helical shape, which is further com- pacted by molecular crowders to occupy a nucleoid-like sub-volume (Fig. 1). With increasing cell length, the longitudinal size of the chromosome increases in a non- linear fashion to finally saturate, its morphology gradu- ally opening up while displaying an increasing number of helical turns. For shorter cells and low crowder densi- ties, the chromosome extension varies non-monotonically with cell size, which we show is associated with a ra- dial to longitudinal spatial reorganization of the crow- ders. Confinement and crowders constrain chain dynam- ics leading to anomalous diffusion. While the scaling ex- ponent for the mean squared displacement of centre of mass grows and saturates with cell length, that of indi- vidual loci displays broad distribution with a well-defined maximum. Despite several experimental efforts, in E.coli bacteria, the mechanism for chromosome segregation re- mains elusive. We propose chromosomal segregation via inter-chromosome repulsion mediated by protein produc- tion. The simulation results show good agreement with experiments.

Corresponding author: debc@iopb.res.in

  1. Fabai Wu, Pinaki Swain, Louis Kuijpers, Xuan Zheng, Kevin Felter, Margot Guurink, Debasish Chaudhuri, Bela Mulder, Cees Dekker, bioRxiv doi: https://doi.org/10.1101/348052.
  2. D. Chaudhuri and B. M. Mulder, Physical Review Letters 108, 268305 (2012).
15:20 to 15:40 Sayantan Majumdar Memory Retention in disordered bio-polymer networks

Adaptive materials can change their mechanical prop- erties depending on external cues in a controlled manner. In this talk, I will describe a novel type of mechanical adaptation in cross-linked networks of F-actin, a ubiqui- tous protein found in the cytoskeleton of eukaryotic cells. We show that shear stress changes the nonlinear mechan- ical response of the network even long after that stress is removed [1]. The duration, magnitude and direction of forcing history all change this mechanical response. While such memory is long-lived, it can be erased simply by force application in the opposite direction. We also show that the observed mechanical adaptation is consis- tent with stress-dependent changes in the nematic order of the constituent filaments. This demonstrates that F- actin networks can exhibit analog read-write mechanical memory.

In disordered condensed matter systems, memory ef- fects originate from out of equilibrium nature of the materials involving slow non-exponential relaxation pro- cesses. Such effects have been observed in systems as diverse as, charge density wave conductors [2], molecular glasses [3], crumpled candy wrappers [4], superconduc- tors [5], granular and amorphous materials [6–8]. In the last part of my talk, I shall also briefly discuss about our preliminary data on non-monotonic stress-relaxation dy- namics in collagen networks (Fig. 1) in the light of other memory encoding condensed matter systems mentioned above.

I would like to thank M.L. Gardel (U. Chicago), A.J. Levine (UCLA), L.C. Foucard (UCLA) for the part of work on actin networks. I thank M.K. Firoz (RRI), S.R. Nagel (U. Chicago) and D. Hexner (U. Chicago) for the ongoing work on memory dynamics in collagen networks. I acknowledge SERB (DST) for support through a Ra- manujan Fellowship.

Corresponding author:  smajumdar@rri.res.in

  1. S. Majumdar, L. C. Foucard, A.J. Levine, and M.L. Gardel, Soft Matter 14, 2052 (2018).
  2. R.M. Fleming, and L. F. Schneemeyer, Phys. Rev. B 33, 2930 (1986).
  3. A. Amir, Y. Orega, and Y. Imry, PNAS 109, 1850 (2012).
  4. Y. Lahini, et al., Phys. Rev. Lett., 118, 085501 (2017).
  5. P. Anderson, Phys. Rev. Lett., 9, 309 (1962).
  6. J. B. Knight, et al., Phys. Rev. E, 51, 3957 (1995).
  7. J. D. Paulsen, N. C. Keim, and S. R. Nagel, Phys. Rev. Lett., 113, 068301 (2014).
  8. D. Fiocco, G. Foffi, and S. Sastry, Phys. Rev. Lett., 112, 025702 (2014).
15:40 to 16:00 -- Coffee Break
16:00 to 17:00 Daan Frenkel From self-assembly to cell recognition (Infosys-ICTS Chandrasekhar - Lecture 2)

A holy grail of nano-technology is to create truly complex, multi-component structures by self-assembly. Most self-assembly has focused on the creation of "structural complexity". In my talk, I will discuss "Addressable Complexity": the creation of structures that contain hundreds or thousands of distinct building blocks that all have to find their place in a 3D structure. Experiments have demonstrated the feasibility of making such structures. Simulation and theory yield surprising insights that can inform the design of novel structures and materials. Surprisingly, the design principles for addressable self-assembly may provide a tool to distinguish different cell surfaces.

17:00 to 18:30 -- Poster Session
19:00 to 22:00 -- Workshop Dinner
Thursday, 30 August 2018
Time Speaker Title Resources
09:00 to 09:45 Alexei Tkachenko O​nset of natural selection and "reversal of the Second Law" In population of autocatalytic heteropolymers

The second law of thermodynamics states that the entropy of a closed system increases with time. Life represents a remarkable example of the opposite trend in an open, non-equilibrium system. Indeed, both informational and thermodynamic entropies decrease in the course of biological evolution reflecting ever-increasing complexity of living organisms and their communities \cite{schroedinger}. Conceptually, the problem of the origin of life can be viewed as a search for the simplest physical system capable of such spontaneous reduction of entropy and growth of complexity \cite{anderson}.

Self-replicating systems based on information-coding polymers are of crucial importance in biology. We have carried out a general theoretical and numerical analysis of the problem of spontaneous emergence of autocatalysis for heteropolymers capable of template-assisted ligation driven by cyclic changes in the environment \cite{JCP}. One of our key results is the existence of the first order transition between the regime dominated by free monomers and that with a self-sustaining population of sufficiently long chains. We provide a simple, mathematically tractable model supported by numerical simulations, which predicts the distribution of chain lengths and the onset of autocatalysis in terms of the overall monomer concentration and two fundamental rate constants.

The template-assisted ligation allows for heritable transmission of the information encoded in chain sequences thus opening up the possibility of long-term memory and evolvability in such systems. In order to explore this scenario, we focus at a reduced version of our original model \cite{arxiv}, by assuming that a template of just two ‘letters’ long is sufficient to catalyze a ligation of two chain ends. Within this reduced model, we can study both numerically and analytically the evolution of the sequence pool of such autocatalytic heteropolymers made of Z types of monomers (‘letters’). Remarkably we find that the sequence entropy, initially at its maximum (consistent with the Random Sequence Approximation used in \cite{JCP}), gets slowly reduced to a much lower value. A closer analysis shows that out of...

Our model, while not detailing specific chemical realization, describes a generic mechanism of formation of long autocatalytic heteropolymers. Furthermore, we show that this system is inherently unstable with respect to symmetry breaking in the sequence space. This leads to reduction of sequence entropy, signaling a spontaneous increase in the information. This can be interpreted as an onset of Darwinian behavior, and may explain future emergence of the natural selection.

The sequence information entropy in a pool of autocatalitic heteropolymers (black lines), and the natural logarithm of the number of surviving two-letter words, 2-mers (red lines) plotted vs. time in 5 different realizations of our system. b)-c) The heatmap visualizing concentrations of 2-mers at the early (b) and late (c) stages of the system’s evolution.

Acknowledgements

This research used resources of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704.

  1. {schroedinger} Schr\"{o}dinger E. What is Life – the Physical Aspect of the Living Cell. Cambridge: Cambridge University Press.; 1944. NB: Strictly speaking, due to the exchange of energy and material with the environment, the appropriate measure of the reduction of thermodynamic entropy by living systems is the local accumulation of Gibbs free energy.
  2. {anderson} P. W. Anderson, Proc. Natl. Acad. Sci. U. S. A. 80, 3386 (1983)
  3. {JCP} A. V. Tkachenko, S. Maslov, J. Chem. Phys. 143, 04510 (2016)
  4. A. V. Tkachenko, S. Maslov, arXiv:1710.06385 (2017), to be published.
09:45 to 10:30 James Swan Out-of-Equilibrium Self-Assembly of Mutually Polarizable Nanoparticle Suspensions in Toggled External Fields

Structured materials self-assembled from dispersions of nanoparticles and colloids have numerous demonstrated applications including wave guides for optical computing, microlens arrays for energy harvesting, and porous electrodes for energy storage. As the particles self-assemble under a steady driving force, a thermodynamic constraint on the phase separation kinetics forces a tradeoff between quality of the self-assembled microstructure and its rate of formation. This is a key difficulty preventing adoption of self-assembled nanoparticle materials at scale. Dynamically self-assembling dispersions with interactions that vary in time do not have this constraint and offer a promising method to suppress kinetic arrest while accelerating growth of ordered nanostructures. For dispersions of polarizable dielectric or paramagnetic nanoparticles, varying the particle interactions in time is easily achieved by toggling the external electric or magnetic field on and off cyclically in time. Because of the cyclic driving force, materials formed by toggled self-assembly are dissipative and out-of-equilibrium, and therefore are classified as active matter, along with particles that swim, grow, or self-rotate. As toggled self-assembly cannot be understood in terms of equilibrium thermodynamics, new theories must be developed before it can be used to reliably fabricate nanomaterials.

I have developed a computational and theoretical model for dispersions of mutually polarizable nanoparticles in steady or toggled external fields. The model takes into account polarization from both the external field and from disturbance fields generated by induced dipoles on surrounding particles. Using Brownian dynamics simulations, I show that cyclically toggling the external field can avoid kinetic barriers and yield large, well-ordered crystalline domains in these dispersions. The rate of phase separation, local and global quality of the self-assembled structures, and range of tunable parameters leading to acceptable self-assembly are all enhanced with toggled fields compared to steady fields. Toggling can also stabilize new phases that are never observed in steady fields, such as fluid-fluid coexistence or body-centered-orthorhombic crystal. The growth mechanism and terminal structure of the dispersion are easily controlled by parameters of the toggling protocol, allowing for selection of processes that yield rapidly self-assembled, low defect structures. Although structures formed via toggled self-assembly are inherently out-of-equilibrium, I show that they can be understood in terms of equations of state valid for steady fields. I perform thermodynamic calculations that predict the out-of-equilibrium terminal states in terms of the parameters of the toggling protocol.

10:30 to 10:55 -- Coffee break
10:55 to 11:40 Suri Vaikuntanathan Dissipation induced transitions in soft matter systems
11:40 to 12:25 M. Scott Shell Systematic multiscale models and physics using the relative entropy

Many molecular processes involve ranges of length and time scales that cannot be tackled with atomic-scale simulations. Instead, coarse-grained molecular models are necessary to interrogate such systems from a theoretical point of view. We discuss a fundamental approach to the identification of such models and more generally of emergent physical behavior from many-body systems. We proposed that a quantity called the relative entropy measures the information lost upon coarse graining and is the natural thermodynamic metric for such tasks [1,2]; its minimization provides a universal variational principle for coarse-graining [3,4]. In particular, this broad statistical-mechanical framework can improve simulation models of complex biomolecular and liquid-state systems, and uncover important driving forces and degrees of freedom [4–6]. We discuss conceptual and numerical aspects of this approach and illustrate its use in several case studies, including our recent efforts to improve models of hydrophobic interactions and complex mixtures using mean-field, multibody interaction potentials inspired by embedded atom models of metallic systems [7,8].

Corresponding author:  michael.gruenwald@utah.edu

  1. M. S. Shell, J. Chem. Phys. 129, 144108 (2008).
  2. M. S. Shell, in Advances in Chemical Physics, edited by S. A. Rice and A. R. Dinner (John Wiley & Sons, Inc., 2016), pp. 395–441.
  3. A. Chaimovich and M. S. Shell, Phys. Rev. E 81, 060104 (2010).
  4. A. Chaimovich and M. S. Shell, J. Chem. Phys. 134, 094112 (2011).
  5. S. Carmichael and M. S. Shell, J. Phys. Chem. B 116, 8383 (2012).
  6. A. Chaimovich and M. S. Shell, Phys. Rev. E 88, 052313 (2013).
  7. T. Sanyal and M. S. Shell, The Journal of Chemical Physics 145, 034109 (2016).
  8. T. Sanyal and M. S. Shell, J. Phys. Chem. B 122, 5678 (2018).
12:25 to 12:45 Sarika Bhattacharya Glassforming ability of a binary mixture: The role of entropy
12:45 to 14:15 -- Lunch
14:15 to 15:00 Prabal Maiti Two-phase thermodynamic(2PT) model for efficient entropy calculation in liquid state
15:00 to 15:20 Apratim Chatterjee Role of special cross-links in the organization of DNA-polymer at micron length scales
15:20 to 15:40 Anand Srivastava Lipids degeneracy in the (sub-100nm) membrane organization: Thermodynamics costs behind maintaining complex lipid diversity

The rich structural complexity of biological mem- branes arises from the chemical diversity of its constituents. Di↵erential inter and intra-molecular interactions result in preferential segregation and clustering of certain types of lipids and proteins, giving rise to a variety of lateral organization on the membrane surface. Recently, Edward Ly- man’s group at Delaware carried out multiple long timescales all-atom molecular dynamics simulations (tens of microseconds long) with carefully chosen lipid compositions to reproduce a variety of phases [1, 2]. We focus on the systems that exhibit liquid- ordered and liquid-disordered (Lo/Ld) co-existence. The three systems with their fractional composi- tions are (i) PSM/POPC/Chol (0.47/0.32/0.21) (ii) PSM/DOPC/Chol (0.43/0.38/0.19) (iii) DPPC/DOPC/Chol (0.37/0.36/0.27).

We analyze these trajectories and numerically calcu- late the degree of non-affineness of individual lipids in their local neighborhood and their topological re- arrangements [3]. We use these data to distinguish between the Lo and Ld regions in the membrane sys- tem at molecular length scales [4].

The three chosen systems exhibit di↵erent molecular- level sub-structures and unique Lo/Ld interface boundaries. We also explore the molecular-origin of this variety in organization using tools from simple statistical mechanics theories. And try to quantify the thermodynamics cost of arriving at a given mem- brane sub-structure using a di↵erent lipid types and compositions.

The authors thank Edward Lyman (University of Delaware, USA) for sharing the AA simulation trajec- tories, which was generously made available by D.E. Shaw Research. AS would also like to thank the IISc- Bangalore for the start-up grant and the DST, India for the Early Career Award.

Corresponding author:  anand@iisc.ac.in

  1. A. J. Sodt, R. W. Pastor, and E. Lyman, Biophys. J, 109, 948-955 (2015)
  2. A. J. Sodt, M. L. Sandar, K. Gawrisch, R. W. Pastor, and E. Lyman, JACS, 136, 725-732 (2014)
  3. M. Falk and J. Langer, PRE, 57, 7192-7203 (1998).
  4. S. S. Iyer*, M. Tripathy*, and A. Srivastava, Biophys. J, 115, 117-128 (2018) *Contributed Equally
15:40 to 16:00 -- Coffee break
16:00 to 17:00 Daan Frenkel Entropy production and phoretic transport (Infosys-ICTS Chandrasekhar - Lecture 3)

It sounds so innocent: `Heat never spontaneously flows from cold to hot’, but almost nothing in this statement is as simple as it seems. In my talk, I will consider the microscopic mechanism by which thermal gradients cause flow along liquid/solid interfaces. In particular, I will discuss the problems in formulating a correct microscopic description of such `phoretic’ transport processes. Phoretic transport becomes increasingly relevant, as experiments probe transport in nanoscale channels. It turns out that our microscopic understanding of flows driven by thermodynamic, rather than mechanical, forces is far from complete. 

Friday, 31 August 2018
Time Speaker Title Resources
09:00 to 09:45 Guruswamy Kumaraswamy Why are ice templated particle polymer hybrids flexible?

Macroscopic objects formed from particle assemblies are typically brittle, precluding their use in several ap- plications. We have demonstrated that ice-templating an aqueous dispersion of rigid colloidal particles and polymer, and crosslinking this polymer in the frozen state results in the formation of remarkably flexible colloidal assemblies[1]. Centimeter-scale monoliths prepared in this manner recover elastically after com- pression to 10% of their original size. This is remark- able when we consider that the monoliths are predom- inantly inorganic, with a particle weight fraction of 90%. Monoliths prepared in this manner are soft, with moduli in the range of tens of kPa. The Poisson ratio for monolith deformation can be calculated based on the change in sample dimensions during compression, and from the ratio of shear and Young’s moduli. The methods are consistent, and yield values close to zero. The scaling of moduli with density suggests the me- chanical response of the monolith in the linear regime is governed by thickening of the pore walls, rather than wall bending. For higher strains, there is a dra- matic increase in stress corresponding to buckling of pore walls.

The moduli of the monoliths increase linearly with temperature, indicating that the mechanical response is entropic in origin. We have demonstrated that flex- ible elastic hybrid monoliths can be prepared using different particles, different polymers and even dif- ferent crosslinking chemistries. Therefore, the me- chanical response appears to be a function largely of the microstructure developed by the preparation pro- cess viz. ice templating, followed by crosslinking in the frozen state. We demonstrate that this protocol results in the formation of a unique microstructure: polymers crosslinked in the frozen state form a mesh around particles in the pore walls[2, 3].

Subtle differences in the protocol for assembling nanoparticles play a critical role in determining their properties. Macroporous monoliths that are chemi- cally identical but that are prepared using small vari- ations in the ice templating protocol exhibit quali- tatively different mechanical behaviour, ranging from flexible elastic monoliths to plastic monoliths that fail at low compressive strains. We employ a variety of experimental techniques to characterize the structure and dynamics in these monoliths. We demonstrate that the preparation protocol modulates the spatial variation in crosslink density. Elastic scaffolds have a uniform distribution of crosslinks while scaffolds that have the same average crosslink density but spatially heterogeneous crosslinks exhibit brittle failure[2, 3].

Finally, I show that we can use the same ice tem- plating protocol to form flexible linear chain-like as- semblies that represent a convenient model system to study polymer physics. I will present results on the dynamics of active colloidal chains prepared using this protocol[4].

We would like to acknowledge SERB-Chemical En- gineering PAC, BRNS and IUSSTF for funding. KS, SC and BB acknowledge funding from CSIR and DST- Inspire.

Corresponding author:  g.kumaraswamy@ncl.res.in

  1. R. Rajamanickam, S. Kumari, D. Kumar, S. Ghosh, J. C. Kim, G. Tae, S. Sengupta, G. Kumaraswamy, Chem. Mater. 26, 5161 (2014).
  2. S. Karthika, S. Patil, P. R. Rajamohanan, G. Ku-maraswamy, Langmuir 32, 11623 (2016).
  3. K. Suresh, R. Chulliyil, D. K. Sharma, Ketan, V. R. Kumar, A. Chowdhury, G. Kumaraswamy, Langmuir 34, 4603 (2018).
  4. B. Biswas, R. Manna, A. Laskar, P. B. S. Kumar, R. Adhikari, G. Kumaraswamy, ACS Nano 11, 10025 (2017).
09:45 to 10:30 Michael Gruenwald Ligand effects in the self-assembly of nanocrystals into superlattices

We present a computational study of ligand effects in the self-assembly of non-spherical nanocrystals [1]. We focus on the two particle shapes most often found in experiments (cuboctahedral or truncated octahe- dral) and determine their assembly behavior as a function of ligand length and solvent quality. Our model, which is based on a coarse-grained description of ligands and a schematic representation of solvent effects, reproduces many of the experimentally ob- served superstructures [2–6], including superlattices with partial and short-ranged orientational alignment of nanocrystals [5, 6]. Our simulations show that small differences in nanoparticle size and shape, ligand cov- erage, and solvent conditions, can lead to markedly different self-assembled superstructures due to subtle changes in the free energetics of ligand interactions. These results help explain the large number of differ- ent reported superlattices self-assembled from seem- ingly similar particles and can serve as a guide for the self-assembly of specific superstructures.

We would like to acknowledge IISc, ISRO-STC and SERB-DST for funding this work.

∗ Corresponding author:  michael.gruenwald@utah.edu

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10:30 to 10:55 -- Coffee break
10:55 to 11:40 R. Rajesh Entropy driven phase transitions in hardcore lattice gas models

One of the simplest systems to show phase transitions is a collection of particles that interact only through excluded volume interactions. Well known examples include hard sphere gas which undergoes a liquid-solid freezing transition and long rods which undergo an isotropic-nematic transition, or nearest neighbour ex- clusion models on lattices, also known as hard core lattice gas models. In such systems, all allowed con- figurations have equal energy and hence temperature plays no role, and phases transitions, if any, are driven by gain in entropy.

Simulations of such systems suffer from issues of equi- libration at high densities, especially when the ex- cluded volumes are large, due to long lived metastable states. This has resulted in not many accurate re- sults being known for hard core lattice gas models in three dimensions, or for two dimensional systems close to full packing. In this talk, I will elaborate upon a grand canonical Monte Carlo algorithm that implements cluster moves in an efficient manner which is able to equilibrate such systems even at the fully packed density. By implementing this algorithm, I will discuss recent results that have been obtained for sys- tems of differently shaped particles like rods, squares, cubes, plates, etc. [1, 2].

Corresponding author:  rrajesh@imsc.res.in

  1. N. Vigneshwar, D. Dhar and R. Rajesh, J. Stat. Mech. 2017, 113304 (2017).
  2. D. Mandal, T. Nath and R. Rajesh, Phys. Rev. E 97, 032131 (2018).
11:40 to 12:25 Ning Xu Phase behaviors of soft-core particles at high densities

Soft-core particles interacting via Spring-like repul- sion exhibit multiple reentrant crystallizations with various solid structures. In this talk, we will present our recent observations of the novel two-dimensional melting scenario due to the reentrance and surprising finding of quasicrystals.

According to the KTHNY theory [1–4], the melting of a two-dimensional solid is a two-stage process. There exists an intermediate phase called hexatic phase be- tween solid and liquid. Transitions from solid to hex- atic and from hexatic to liquid are both continuous. Recently, it has been reported that the hexatic-liquid transition of hard particles is discontinuous [5] and the transition can evolve from discontinuous to continuous when the softness of particles is tuned [6]. For soft- core particle systems which reach the first maximum melting temperature T m at a crossover density ρ m , we find that ρ m acts as a transition point. Hexatic-liquid transition at ρ < ρ m exhibits strong first order tran- sition features. There is a density interval in which liquid and hexatic phases coexist. The interval de- creases with increasing temperature and tends to van- ish at T m . When ρ > ρ m , however, the hexatic-liquid transition becomes continuous. Therefore, in soft-core systems with reentrant crystallization, density should affect the nature of the hexatic-liquid transition [7].

At much higher densities after several reentrance, we surprisingly observe the existence of two-dimensional quasicrystals [8]. Up to now, quasicrystals have been found in multi-component systems such as al- loys [9] and in mono-component systems with mul- tiple length scales in particle interactions [10–15] or with anisotropic particles such as tetrahedral and patchy particles [16, 17]. In all these systems, multiple length scales are present in particle size, interaction, or anisotropy, which seem to be the consensual condi- tion for quasicrystals to occur. The quasicrystals that we found are unexpectedly formed by monodisperse, isotropic particles interacting via the simple soft-core potential without multiple length scales. We find not only dodecagonal but also octagonal quasicrystals, which have not been found yet in soft quasicrystals. In our quasicrystals, particles tend to form pentagons. A pentagon surrounded by an n-fold polygon constructs the complex structural unit to develop the n-fold qua- sicrystalline order. In liquid states prior to the liquid- solid transition, we already observe some signs of the development of the quasicrystalline order, including the accumulation of pentagons and the emergence of two competing length scales. We have also verified that our quasicrystals are stable by showing that their formation is independent of history and they have the lowest inherent structure potential energy, compared with other crystalline states.

Corresponding author:  ningxu@ustc.edu.cn

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12:25 to 12:45 Tapati Dutta Growth kinetics of NaCl crystals in a drying drop of gelatin: transition from faceted to dendritic growth

The study of droplets of complex fluids, dried through evaporation, reviewed recently by Sefiane [1, 2] is becoming a rapidly growing field of research. The widespread interest is due to the basic physics aspect as well as promising applications in technology [3], quality control and medical diagnostics [4]. A drying droplet may exhibit a host of features, concentric ring patterns [5, 6], cracks[7, 8], and other interesting mor- phologies. A fact well known since many years is that gels provide a good medium for the growth of crystals [9].

We report a study on the kinetics of drying of a droplet of aqueous gelatin containing sodium chloride. The process of drying recorded as a video clearly shows different regimes of growth leading to a variety of crystalline patterns. Large faceted crystals of mm size form in the early stages of evaporation Fig. 1(a), followed by highly branched multi- fractal patterns with micron sized features Fig. 1(b). We simulate the growth using a simple algorithm incorporating aggre-gation and evaporation, which reproduces the cross- over between the two growth regimes Fig. 1(c - d). As evaporation proceeds, voids form in the gel film. The time development of the fluidvoid system can be characterized by the Euler number. A minimum in the Euler number marks the transition between the two regimes of growth Fig. 2 .

We sincerely thank Abhra Giri for participating in this work.

Corresponding author:  sujata.tarafdar@gmail.com

tapati dutta@sxc.com, tapati mithu@yahoo.com

  1. K. Sefiane, Adv. Colloid Interface Sci., 206, 372381 (2014).
  2. Sujata Tarafdar, Yuri Yu Tarasevich, Moutushi Dutta Choudhury, Tapati Dutta, Duyang Zang, Advances in Condensed Matter Physics, Published on 01 Jan 2018, doi: 10.1155/2018/5214924
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  6. Tapati Dutta,Sujata Tarafdar and Tajkera Khatun,J. Phys. Commun. 2 055023 (2018)
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  8. Z. YongJian, L. ZhengTang, Z. Du Yang, Q. YiMeng and L. KeJun, Sci. China: Phys., Mech. Astron., 56, 17121718 (2013).
  9. Biswajit Roy, Moutushi Dutta Choudhuri, Tapati Dutta, Sujata Tarafdar, Applied Surface Science 357 10001006 (2015)
12:45 to 14:15 -- Lunch
14:15 to 15:00 Shashi Thutupalli Towards controlled assembly in active matter

We describe our efforts towards constructing synthetic active particle systems capable of tunable assemblies and organised structures. Active particles, including swimming microorganisms, autophoretic colloids and droplets, are known to self-organize into ordered struc- tures at fluid-solid boundaries. The entrainment of particles in the attractive parts of their spontaneous flows has been postulated as a possible mechanism underlying this phenomenon. Here, combining exper- iments, theory and numerical simulations, we demon- strate the validity of this flow-induced ordering mech- anism in a suspension of active emulsion droplets. We show that the mechanism can be controlled, with a variety of resultant ordered structures, by simply al- tering hydrodynamic boundary conditions.

Thus, for flow in Hele-Shaw cells, metastable lines or stable traveling bands can be obtained by varying the cell height. Similarly, for flow bounded by a plane, dynamic crystallites are formed. At a no-slip wall the crystallites are characterised by a continuous out- of-plane flux of particles that circulate and re-enter at the crystallite edges, thereby stabilising them. At an interface where the tangential stress vanishes the crystallites are strictly two-dimensional, with no out- of-plane flux. We rationalize these experimental re- sults by calculating, in each case, the slow viscous flow produced by the droplets and the dissipative, long- ranged, many-body active forces and torques between them. The results of numerical simulations of motion under the action of the active forces and torques are in excellent agreement with experiments. Our work [1] elucidates the mechanism of flow-induced phase sepa- ration (FIPS) in active fluids, particularly active col- loidal suspensions, and demonstrates its control by boundaries, suggesting new routes to geometric and topological phenomena in active matter.
States of self-organization maintained by entropy pro- duction were studied in the past by the Brussels school and were given the name dissipative structures [2]. Self-organization in active particles, as shown here, appears to be an example of a dissipative structure but one in which the dissipative mechanism and the resultant forces and torques are unambiguously iden- tified.

Corresponding author: Shashi Thutupalli -  shashi@ncbs.res.in

  1. Thutupalli S, Geyer D, Singh R, Adhikari R, and Stone H A (2018) Flow-induced phase separation of active particles is controlled by boundary conditions Proc. Nat. Acad. Sci. 115 (21), 5403-5408.
  2. Kondepudi, D & Prigogine, I. (1998) Modern Ther-modynamics: From Heat Engines to Dissipative Struc-tures. (John Wiley & Sons).
15:00 to 15:45 Ran Ni “Entropic Effects” in Active Hard Spheres

Over the past decade, active hard spheres have be- come a benchmarking model system for studying the non-equilibrium physics in active matter. Although active hard spheres are intrisically out of equilibrium, we still find some equilibrium entropy-like effects in the system to drive the phase transition and self- organization in the system. In particular, I will talk about our recent work on active depletion forces [1], entropy driven active-passive demixing [2], and the formation of strongly hyperuniform fluids in systems of active hard spheres [3].

Corresponding author:  r.ni@ntu.edu.sg

  1. R. Ni, M.A. Cohen Stuart, and P.G. Bolhuis, Phys. Rev. Lett. 114, 018302 (2015).
  2. Z. Ma, Q. Lei, and R. Ni, Soft Matter, 13, 8940 (2017)
  3. Q. Lei, M.P. Ciamarra, and R. Ni, arXiv:1802.03682 (2018)
15:45 to 16:05 Habib Rahbari Characterizing rare fluctuations in soft particulate flows
16:05 to 16:30 -- Closing
16:30 to 17:00 -- Coffee break
Monday, 03 September 2018
Time Speaker Title Resources
11:00 to 12:30 Mukund Thattai Algorithmic biosynthesis of branched carbohydrates in eukaryotes

An algorithm converts inputs to corresponding unique outputs through a sequence of actions. Algorithms are used as metaphors for complex biological processes such as organismal development. Here we make this metaphor rigorous for glycan biosynthesis. Glycans are branched carbohydrate oligomers that are attached to cell-surface proteins and convey cellular identity. Eukaryotic glycans are synthesized by collections of enzymes in Golgi compartments. A compartment can stochastically convert a single input oligomer to a heterogeneous set of possible output oligomers; yet a given type of protein is invariably associated with a narrow and reproducible glycan oligomer profile. Here we resolve this paradox by borrowing from the theory of algorithmic self-assembly. We rigorously enumerate the sources of glycan microheterogeneity: incomplete oligomers via early exit from the reaction compartment; tandem repeat oligomers via runaway reactions; and competing oligomer fates via divergent reactions. We demonstrate how to diagnose and eliminate each of these, thereby obtaining ``algorithmic compartments" that convert inputs to corresponding unique outputs. Given an input and a target output we either prove that the output cannot be algorithmically synthesized from the input, or explicitly construct a succession of algorithmic compartments that achieves this synthesis. Our theoretical analysis allows us to infer the causes of non-algorithmic microheterogeneity and species-specific diversity in real glycan datasets.

Tuesday, 04 September 2018
Time Speaker Title Resources
11:00 to 12:30 Anupam Kundu Dynamics in a Gas-Piston system

Consider a single particle gas confined in one dimension between a heavy piston and a Maxwell thermal reservoir. When the piston is held fixed the particle is expected to reach an equilibrium state after a long time. In the first part I will talk about how does the particle relax to equilibrium. When the piston is released with a force applied on it, it will start moving. But the motion will soon become stochastic due to the collisions with the particle. Is it possible to have an effective Langevin equation description of the piston motion? In the second part, I will talk about our attempt to answer this question.

Wednesday, 05 September 2018
Time Speaker Title Resources
11:00 to 12:30 Oleksiy Tkachenko How to Build a Diamond?

Self-assembly is a key phenomenon in living matter, and at the same time, a booming field of modern material science and engineering. In my talk I will review emerging trends and ideas in this field, and give theorist's perspective on its conceptual challenges. I will discuss the strategy of programmable self-assembly that uses molecular recognition properties of DNA to build nano- and micro-scale building blocks with designed pairwise interactions. This approach opens an entirely new class of theoretical problems in statistical physics. Instead of studying phenomenology of a large system of particles with given properties, we must solve the inverse problem: finding the interactions that would result in a self-assembly of a desired macroscopic or mesoscopic morphology. I will start with a discussion of self-assembly in a very simple binary system of spherical particles, and gradually move towards a greater complexity of both the building blocks and the resulting structures. One structure that is notoriously challenging for self-assembly, and often viewed as a Holy Grail of the field, is a diamond lattice. I will therefore use diamond as a model system to illustrate general principles and specific approaches to programmable self-assembly. Some of those approaches are already implemented in experiments, while others are just theoretical prescriptions.

Thursday, 06 September 2018
Time Speaker Title Resources
11:00 to 12:30 Santosh Ansumali Second law in Discrete Time kinetic theory

The entropic lattice Boltzmann model (ELBM) aims to construct a simplified kinetic picture on a lattice designed to capture the physics of macroscopic flow through simple local micro-scale operations.  

The method is unique in the sense that it enforces the numerical stability of a hydrodynamic solved by insisting on adherence to the thermodynamics at the discrete time level.   This compliance with the H theorem is typically enforced by
searching for the maximal discrete path length corresponding to the zero dissipation state by iteratively solving a nonlinear equation. We demonstrate that an exact solution for the path length can be obtained by
assuming a natural criterion of negative entropy change, thereby reducing the problem of solving an inequality.     Such a discrete space-time map can also be thought as geometric discretization of the dissipative Boltzmann dynamics.  Finally, I will discuss the possibility that such an implicit modeling of unresolved scales of the flow, via the thermodynamic route, may provide a new insight into subgrid modeling of turbulence.

Friday, 07 September 2018
Time Speaker Title Resources
11:00 to 12:30 Mark Miller Encoding Building-Blocks for Programmable Self-Assembly

The self-assembly of discrete objects can take place via many schemes, ranging from the elegant efficiency of certain virus capsids (which assemble from multiple copies of just one protein) to the latest developments in addressable assembly (where every building block is unique). Programmable assembly refers to the ambition of controlling every individual site in a target structure as well as the pathways by which it forms. In this talk I will test different strategies for controlling and optimising the self-assembly of discrete targets using an idealised model of particles with patterned interactions. In particular, I will examine the special challenges that come into play in the case of addressable assembly. In this limit, each building block must be encoded with enough information to find its unique location in the target structure. Furthermore, independently growing structures must avoid becoming mutually incompatible, which would lead to frustration in the assembly process. Along the way, I will describe some new tools for design, simulation and analysis in the context of colloidal self-assembly

Monday, 10 September 2018
Time Speaker Title Resources
11:00 to 12:30 Mark Miller Curved Surfaces and Percolation of Nanorods

In this talk I will present highlights from two independent projects. Apart from the fact that they both deal with soft matter systems, the only (tenuous) link is that they both involve the use of non-standard Monte Carlo techniques that are specialised to the respective tasks.

The first case concerns phase transitions in curved two-dimensional spaces, such as colloidosomes, where colloidal spheres are confined to the surface of a spherical droplet. The curvature, finite extent and thermodynamic ensemble all have pronounced effects on the nucleation process. More exotic toroidal surfaces give rise to some entirely new considerations.

The second case is the percolation transition in composite materials containing carbon nanotubes, where the emergence of a system-spanning network of nanotubes confers electrical conductivity on the material. We have investigated the interplay of length polydispersity and external aligning fields on the percolation threshold of these highly elongated particles, leading to some important general conclusions for optimising the formulation of such materials.

Tuesday, 11 September 2018
Time Speaker Title Resources
11:00 to 12:30 Prabal Maiti Understanding DNA based nanostructures

 

DNA and its crossover motifs are integral components for designing DNA based nanostructure and nanomechanical devices. In this talk I will discuss simulation methodologies to study various DNA based nanostructures. I report MD simulations results on cross-over DNA molecules to obtain a comprehensive understanding of relationship between structure, topology, and stability of various Paranemic crossover (PX/JX) DNA molecules. We present atomistic model of various DNA nanotubes (DNTs) and their elastic properties which will facilitate further studies of these nanotubes in several important nano technological and biological applications. In particular, we introduce a computational design to create atomistic model of 8-helix DNT (8HB) and 6-helix DNT (6HB) along with its two variants, 6HB flanked symmetrically with two double helical DNA pillars (6HB+2) and 6HB flanked symmetrically by three double helical DNA pillars (6HB+3). The measured persistence lengths of these nanotubes are ~10 μm, which is 2 orders of magnitude larger than that of dsDNA. We have also examined the interaction of DNA nanotubes embedded in the lipid bilayer membranes. The Ohmic conductance measured from I-V characteristics of the ions channel varies from 4.3 to 20.6 nS with ionic strength. Finally, I present atomistic model of DNA icosahedron, and study the structure and dynamics of DNA icosahedrons. Our simulations on cargo loaded DNA icosahedra provide insight on the dynamics of the DNA scaffold that gives information not only on polyhedra-cargo interactions, but also interaction of a tag-displaying, cargo-loaded icosahedron with its biological target
Wednesday, 12 September 2018
Time Speaker Title Resources
11:00 to 12:30 Rama Govindarajan Droplet and vortex interactions in the context of clouds

In this talk I will discuss the dynamics of droplets in the vicinity of vortices. The dynamics is described by simple parameter-free equation which have a boundary layer structure. Droplets within a critical distance from the vortex centre can participate in caustics events, and seed rapid droplet growth by collisions and coalescence. Our simulations provide evidence for this in three dimensions. I will then discuss how small droplets falling under gravity are affected by the Basset history force, a force which is normally extremely cumbersome to compute, but which we solve by an efficient method. Finally I will discuss how turbulence is affected by condensation on droplets. I will discuss some of these in the context of clouds.

Friday, 14 September 2018
Time Speaker Title Resources
11:00 to 12:30 Atsushi Ikeda Viscosity divergence and dynamical slowing down at the jamming transition

Jamming transition of athermal particles is characterized by the divergence of the viscosity. This transition looks very similar to the glass transition, but there are several key differences. One of the differences is that the dynamical slowing down is apparently absent in the jamming transition. In this talk, I will report our recent study on the dynamics near the jamming transition. We especially focus on the dynamics in the simplest setting. i.e. relaxation from the random configuration of soft particles without shear. I show that the relaxation exhibits remarkable slowing down. I also show that this relaxation is dominated by a non trivial anomalous mode and is quantitatively related to the viscosity divergence.

Monday, 17 September 2018
Time Speaker Title Resources
09:30 to 11:00 Chandan Dasgupta Statistical mechanics of systems of interacting classical particles (Lecture 1)

Lecture 1: Mayer cluster expansion for non-ideal gas, correlation and response functions

11:00 to 11:30 -- Coffee
11:30 to 13:00 Sanat Kumar The Role of Chain Conformational Entropy on Self-Assembly of Surfactants, Polymers and Nanoparticles (Lecture 1)

“Self-assembly (SA) in the classic sense can be defined as the spontaneous and reversible organization of molecular units into ordered structures by non-covalent interactions. The first property of a self-assembled system that this definition suggests is the spontaneity of the self-assembly process: the interactions responsible for the formation of the self-assembled system act on a strictly local level—in other words, the nanostructurebuilds itself. “ - WIkipedia

This lecture will first focus on the basics of self-assembly and will show that this process only occurs for special systems. The ideas of Israelachvili on the critical micelle concentration and the packing parameter will be introduced. This lecture then naturally leads to delineating the conformational entropy of the surfactant tail, which is driven by ideas of entropic elasticity first espoused by Flory and deGennes. The application of these ideas to block copolymer self-assembly, to polymer crystallization and nanoparticle self-assembly will be explored in lecture 3.

Texts:

Israelachvili, Intermolecular and Surface Forces, Academic Press, 1992

Rubinstein, Colby Polymer Physics, Oxford, 2003

Lecture 1 (Israleachvili, Chapters 16,17)

  1. What is self-assembly. Examples including Crystallization – colloids, polymers; Surfactants – Small molecules, Block copolymers; Nanoparticles – their growth, assembly; Self-assembled monolayers; Templated Synthesis from Surfactant Assemblies – ZSM 5; Lipid Bilayers….

  2. Mass action law- finite clusters vs. phase separation

  3. CMC

  4. Packing parameter idea

13:00 to 14:30 -- Lunch
14:30 to 16:00 Dov Levine Order, Entropy, Information, and Compression (Lecture 1)

In my lectures, I will begin with an idiosyncratic discussion of the idea of organization, ordering, and order. I will then introduce some relevant ideas from information theory, including Shannon entropy, Kolmogorov complexity, and elementary concepts from coding theory, followed by to a discussion of data compression and its relation to Shannon entropy. This will lead to a resume of results from ongoing research into the identification and quantification of order in systems far from equilibrium.

15:30 to 16:00 -- Coffee
16:30 to 17:30 -- Tutorial
Tuesday, 18 September 2018
Time Speaker Title Resources
09:30 to 11:00 Chandan Dasgupta Statistical mechanics of systems of interacting classical particles (Lecture 2)

Lecture 2: Elements of liquid-state theory, introduction to classical density functional theory

11:00 to 11:30 -- Coffee
11:30 to 13:00 Sanat Kumar The Role of Chain Conformational Entropy on Self-Assembly of Surfactants, Polymers and Nanoparticles (Lecture 2)

Lecture 2 (Rubinstein & Colby, Chapters 2, 3, 5)

  1. Importance of chain entropy

  2. Flory entropy idea

  3. Entropic springs

  4. Scaling

  5. Chain dimensions under stretching, good solvent etc.

13:00 to 14:30 -- Lunch
14:30 to 16:00 Dov Levine Order, Entropy, Information, and Compression (Lecture 2)

In my lectures, I will begin with an idiosyncratic discussion of the idea of organization, ordering, and order. I will then introduce some relevant ideas from information theory, including Shannon entropy, Kolmogorov complexity, and elementary concepts from coding theory, followed by to a discussion of data compression and its relation to Shannon entropy. This will lead to a resume of results from ongoing research into the identification and quantification of order in systems far from equilibrium.

15:30 to 16:00 -- Coffee
16:30 to 17:30 -- Tutorial
Wednesday, 19 September 2018
Time Speaker Title Resources
09:30 to 11:00 Sanat Kumar The Role of Chain Conformational Entropy on Self-Assembly of Surfactants, Polymers and Nanoparticles (Lecture 3)

Lecture 3 (Various sources)

  1. Application of these ideas to BCP self-assembly

  2. Application to polymer crystallization

  3. Nanoparticle self assembly

  4. How do you measure this - SANS.

11:00 to 11:30 -- Coffee
11:30 to 13:00 Bulbul Chakraborty Statistical Mechanics of Athermal Systems: Edwards Ensemble, Entropy and Friction (Lecture 1)

Lecture 1: Introduction to Edwards’ ideas, Microcanonical and Canonical Ensembles, Concept of Compactivity and Angoricity.

 

13:00 to 14:30 -- Lunch
14:30 to 16:00 Sriram Ramaswamy Dynamics, Entropy Production & Defects in Active Matter (Lecture 1)

I will begin with a general Langevin framework for active matter dynamics [1] in which the “active terms” are directly linked to a driving force most naturally interpreted as a chemical potential imbalance between fuel and reaction products. I will consider the entropy- production properties of specific instances of such equations of motion for individual active particles as well as for active field theories [2, 3]. I will also discuss the defect-unbinding transition of active nematic systems [4], which has a natural energy-entropy aspect.

I acknowledge support from the Tata Education and Development Trust and from a J C Bose Fellowship of the Science & Engineering Research Board.

Corresponding author: sriram@iisc.ac.in

  1. S Ramaswamy, J Stat Mech 2017:054002
  2. L P Dadhichi, A Maitra and S Ramaswamy, in preparation
  3. C Nardini et al., Phys Rev X 7, 021007 (2017).
  4. S Shankar et al., arXiv:1804.06350 
15:30 to 16:00 -- Coffee
16:30 to 17:30 -- Tutorial
Thursday, 20 September 2018
Time Speaker Title Resources
09:30 to 11:00 Bulbul Chakraborty Statistical Mechanics of Athermal Systems: Edwards Ensemble, Entropy and Friction (Lecture 2)

Lecture 2:  The dual networks of jammed packings:  Contact network and Force Tilings

11:00 to 11:30 -- Coffee
11:30 to 13:00 Dov Levine Order, Entropy, Information, and Compression (Lecture 3)

In my lectures, I will begin with an idiosyncratic discussion of the idea of organization, ordering, and order. I will then introduce some relevant ideas from information theory, including Shannon entropy, Kolmogorov complexity, and elementary concepts from coding theory, followed by to a discussion of data compression and its relation to Shannon entropy. This will lead to a resume of results from ongoing research into the identification and quantification of order in systems far from equilibrium.

13:00 to 14:30 -- Lunch
14:30 to 16:00 Sriram Ramaswamy Dynamics, Entropy Production & Defects in Active Matter (Lecture 2)

I will begin with a general Langevin framework for active matter dynamics [1] in which the “active terms” are directly linked to a driving force most naturally interpreted as a chemical potential imbalance between fuel and reaction products. I will consider the entropy- production properties of specific instances of such equations of motion for individual active particles as well as for active field theories [2, 3]. I will also discuss the defect-unbinding transition of active nematic systems [4], which has a natural energy-entropy aspect.

I acknowledge support from the Tata Education and Development Trust and from a J C Bose Fellowship of the Science & Engineering Research Board.

Corresponding author: sriram@iisc.ac.in

  1. S Ramaswamy, J Stat Mech 2017:054002
  2. L P Dadhichi, A Maitra and S Ramaswamy, in preparation
  3. C Nardini et al., Phys Rev X 7, 021007 (2017).
  4. S Shankar et al., arXiv:1804.06350 
15:30 to 16:00 -- Coffee
Friday, 21 September 2018
Time Speaker Title Resources
09:30 to 11:00 Bulbul Chakraborty Statistical Mechanics of Athermal Systems: Edwards Ensemble, Entropy and Friction (Lecture 3)
11:00 to 11:30 -- Coffee
11:30 to 13:00 Sriram Ramaswamy Dynamics, Entropy Production & Defects in Active Matter (Lecture 3)

I will begin with a general Langevin framework for active matter dynamics [1] in which the “active terms” are directly linked to a driving force most naturally interpreted as a chemical potential imbalance between fuel and reaction products. I will consider the entropy- production properties of specific instances of such equations of motion for individual active particles as well as for active field theories [2, 3]. I will also discuss the defect-unbinding transition of active nematic systems [4], which has a natural energy-entropy aspect.

I acknowledge support from the Tata Education and Development Trust and from a J C Bose Fellowship of the Science & Engineering Research Board.

Corresponding author: sriram@iisc.ac.in

  1. S Ramaswamy, J Stat Mech 2017:054002
  2. L P Dadhichi, A Maitra and S Ramaswamy, in preparation
  3. C Nardini et al., Phys Rev X 7, 021007 (2017).
  4. S Shankar et al., arXiv:1804.06350 
13:00 to 14:30 -- Lunch
14:30 to 15:15 Guiseppe Foffi Beyond isotropic models for dynamically arrested colloids, introducing directionality

In this talk I will briefly review the dynamic phase diagram of colloidal particle interacting with a short-ranged attractive interactions. This realistic model posses a number of exotic properties such as a reentrant melting, two different kid of glass, an arrested phase separation resulting in a gel structure. Most of this unusual phenomenology has been now confirmed in experiments and computer simulations.

The above scenario, is restricted to isotropic colloid, however in recent years a lot of interest has been devoted to the effect of directional attractive forces due to the progress in particles synthesis. I will present some recent results on the effect of directionality on the dynamics of these systems in connection, in particular, with the idea of locally favoured structure of a glass former.

15:15 to 16:00 Hideyuki Mizuno Vibrational properties in the continuum limit of amorphous solids

The thermal properties of crystalline solids follow universal laws that are explained in terms of phonons. Amorphous solids are also characterized by universal laws that are, however, anomalous with respect to their crystalline counterparts. These anomalies begin to emerge at very low temperatures, suggesting that the vibrational properties of amorphous solids differ from phonons at very low frequencies, even in the continuum limit. In this talk, I will show that phonons coexist with soft localized modes in the continuum limit. I will also show that the phonons follow the Debye law, whereas the soft localized modes follow another universal non-Debye law. Finally I will discuss about origin of the soft localized modes.

15:30 to 16:00 -- Coffee
16:30 to 17:30 -- Tutorial
Monday, 24 September 2018
Time Speaker Title Resources
09:30 to 11:00 Srikanth Sastry Phenomenology of glass forming liquids and glasses - Lecture 1

An overview will be presented of the phenomenolog y of glass forming liquids, glasses, and the glass transition, as a prelude to more extended expositions of specific themes that will be explored in the subsequent lectures in the school. The topics covered will include the nature and characterization of the dynamics, and dynamical slow down in glass forming liquids, the role of configurational entropy in descriptions of such dynamical slow down, heterogeneous dynamics, growing length scales in glass formers, and a mention of related topics concerning yielding of glasses and jamming.

11:00 to 11:30 -- Coffee
11:30 to 13:00 Jorge Kurchan Entropy in the evolution of almost integrable systems

Almost integrable systems are ubiquitous: weakly nonlinear waves, planetary systems, globular clusters, the Fremi-Pasta-Ulam problem, many well studied Quantm chains... The approach to equilibrium is slow, because it is done precisely through the integrability breaking. On the other hand, they offer us an opportu- nity of understanding the precise role played by Entropy at each stage, because the evolution is, in a sense, reversible.

  1. Integrable systems. Constants of motion. Approximate constants of motion.
  2. Examples: solar system, Fermi-Pasta-Ulam chain, weak turbulence.
  3. Generalized Gibbs Ensemble. Approach to equilibrium.
  4. A Fluctuation Theorem
13:00 to 14:30 -- Lunch
14:30 to 16:00 Srikanth Sastry Phenomenology of glass forming liquids and glasses (Lecture 2)

An overview will be presented of the phenomenology of glass forming liquids, glasses, and the glass transition, as a prelude to more extended expositions of specific themes that will be explored in the subsequent lectures in the school. The topics covered will include the nature and characterization of the dynamics, and dynamical slow down in glass forming liquids, the role of configurational entropy in descriptions of such dynamical slow down, heterogeneous dynamics, growing length scales in glass formers, and a mention of related topics concerning yielding of glasses and jamming.

15:30 to 16:00 -- Coffee
16:30 to 17:30 -- Tutorial
Tuesday, 25 September 2018
Time Speaker Title Resources
09:30 to 11:00 Francesco Sciortino Entropy in Self-Assembly (Lecture 1)

I will discuss the role of entropy in some of the most relevant self-assembly processes. The outline of the lectures is the following:

Introduction

  • Entropy and Translational Order: Hard Sphere Crystallisation [1]
  • Entropy and Orientational Order: Transition [2]
  • Entropy Attracts: Depletion Interactions [3]
  • Entropy Attracts: tions [4]
  • Competition between energy and entropy in self-assembly [5]
  • Entropy and flexibility in networks [6]

Corresponding author: francesco.sciortino@uniroma1.it

  1. B. Alder and T. Wainwright, The Journal of chemical physics 27, 1208 (1957).
  2. L. Onsager, Annals of the New York Academy of Sci-ences 51, 627 (1949).
  3. H. N. Lekkerkerker and R. Tuinier, Colloids and the depletion interaction, Vol. 833 (Springer, 2011).
  4. A. Zilman, J. Kieffer, F. Molino, G. Porte, and S. Safran, Physical review letters 91, 015901 (2003).
  5. F. Sciortino, Soft Matter Self-Assembly, Varenna School, Italian Physical Society 193, 1 (2016).
  6. F. Smallenburg and F. Sciortino, Nature Physics 9, 554 (2013).
11:00 to 11:30 -- Coffee
11:30 to 13:00 Francesco Zamponi Mean field theory of the glass transition (Lecture 1)

The development of a mean field theory of glasses started in the 80s, through the work of Kirkpatrick, Thirumalai and Wolynes. They identified a class of mean field spin glass models, whose qualitative behav- ior is very similar to the one of supercooled liquid and glasses measured in the laboratory. They proposed that these spin glass models could serve as represen- tative of a broad universality class, called the Ran- dom First Order Transition (RFOT) class, in which the glass transition would fall, at least at the mean field level. To substantiate this claim, they proposed that a system of d-dimensional interacting particles would fall in this class in the d → ∞ limit [1].

During the subsequent two decades, a lot of work has been done on RFOT spin glass models, which provided many important predictions on the thermodynamics and dynamics of RFOT systems: glass transition, aging, effective temperatures, complexity, dynamical heterogeneities... However, proving that the original conjecture of [1] is correct took another decade, and the program was completed in the last few years.

In these lectures I will review the solution of parti- cle systems in d → ∞. I will show that the behavior is precisely the one of the RFOT universality class. I will start by the study of the equilibrium dynamics and show the existence of a dynamical glass transition similar to the one of Mode-Coupling Theory [2]. Next, I will show how the long time limit of the dynamics in the glass phase can be studied via the replica method using the “state following” or Franz-Parisi construc- tion [3]. Finally, I will briefly discuss the Gardner and jamming transitions [4].

During the lectures, physical concepts such as the dy- namical glass transition, the complexity, the Kauz- mann transition, the out-of-equilibrium glass state, and the criticality of jamming will be discussed. Methodologically, we will introduce dynamical and replica techniques. The lectures are based on a book which is currently being written [5].

Corresponding author: www.phys.ens.fr/∼zamponi

  1. T.R.Kirkpatrick and P. G. Wolynes, “Connections be-tween some kinetic and equilibrium theories of the glass transition”, Physical Review A 35, 3072 (1987).
  2. T.Maimbourg, J.Kurchan, and F.Zamponi, “Solution of the dynamics of liquids in the large-dimensional limit”, Physical Review Letters 116, 015902 (2016).
  3. C.Rainone, P.Urbani, H.Yoshino, and F.Zamponi, “Following the evolution of hard sphere glasses in in-finite dimensions under external perturbations: com-pression and shear strain”, Physical Review Letters 114, 015701 (2015).
  4. P.Charbonneau, J.Kurchan, G.Parisi, P.Urbani, F.Zamponi, “Fractal free energy landscapes in struc-tural glasses”, Nature Communications 5, 3725 (2014).
  5. G.Parisi, P.Urbani, F.Zamponi, “Theory of simple glasses”, book in preparation (Cambrige University Press).
13:00 to 14:30 -- Lunch
14:30 to 16:00 Ludovic Berthier Measuring the configurational entropy in computer simulations of deeply supercooled liquids (Lecture 1)

In these lectures, I will employ the material presented in the introductory lectures, in particular the basics of liquid state theory and statistical mechanics to explain how the configurational entropy of supercooled liquids can be measured in computer simulations of supercooled liquids [1].

I will first explain why we must care about the configurational entropy, how it is defined and what are the conceptual problems associated to this important quantity, from the ill-defined concept of thermodynamic metastability to issues related to polydisperse liquid models.

I will then talk about computer simulations of super- cooled liquids, how they are done, and what can be hoped to be achieved using this important tool. In particular, I will emphasize the new opportunities offered by the recent development of the SWAP algorithm [2] to explore more ambitiously than before the thermodynamic properties of deeply supercooled liquids [3].

Then I will show how in practice one defines and mea- sures using computer simulations various proxies for the configurational entropy, from the potential energy landscape approach, from the Frenkel-Ladd thermodynamic construction, from the Franz-Parisi free energy, and from the point-to-set correlation length measurement.

These lectures have strong connections with the mean- field results presented in the parallel lectures by F. Zamponi and J. Kurchan.

Corresponding author: ludovic.berthier@umontpellier.fr

  1. L. Berthier and G. Biroli, Theoretical perspective on the glass transition and amorphous materials, Rev. Mod. Phys. 83, 587 (2011).
  2. A. Ninarello, L. Berthier, and D. Coslovich, Models and algorithms for the next generation of glass transition studies, Phys. Rev. X 7, 021039 (2017).
  3. L. Berthier, P. Charbonneau, D. Coslovich, A. Ninarello, M. Ozawa, and S. Yaida, Configurational entropy measurements in extremely supercooled liquids that break the glass ceiling, Proc. Natl. Acad. Sci U. S. A. 114, 11356 (2017).
15:30 to 16:00 -- Coffee
16:30 to 17:30 -- Tutorial
Wednesday, 26 September 2018
Time Speaker Title Resources
09:30 to 11:00 Francesco Zamponi Mean field theory of the glass transition (Lecture 2)

The development of a mean field theory of glasses started in the 80s, through the work of Kirkpatrick, Thirumalai and Wolynes. They identified a class of mean field spin glass models, whose qualitative behav- ior is very similar to the one of supercooled liquid and glasses measured in the laboratory. They proposed that these spin glass models could serve as represen- tative of a broad universality class, called the Ran- dom First Order Transition (RFOT) class, in which the glass transition would fall, at least at the mean field level. To substantiate this claim, they proposed that a system of d-dimensional interacting particles would fall in this class in the d → ∞ limit [1].

During the subsequent two decades, a lot of work has been done on RFOT spin glass models, which provided many important predictions on the thermodynamics and dynamics of RFOT systems: glass transition, aging, effective temperatures, complexity, dynamical heterogeneities... However, proving that the original conjecture of [1] is correct took another decade, and the program was completed in the last few years.

In these lectures I will review the solution of parti- cle systems in d → ∞. I will show that the behavior is precisely the one of the RFOT universality class. I will start by the study of the equilibrium dynamics and show the existence of a dynamical glass transition similar to the one of Mode-Coupling Theory [2]. Next, I will show how the long time limit of the dynamics in the glass phase can be studied via the replica method using the “state following” or Franz-Parisi construc- tion [3]. Finally, I will briefly discuss the Gardner and jamming transitions [4].

During the lectures, physical concepts such as the dy- namical glass transition, the complexity, the Kauz- mann transition, the out-of-equilibrium glass state, and the criticality of jamming will be discussed. Methodologically, we will introduce dynamical and replica techniques. The lectures are based on a book which is currently being written [5].

Corresponding author: www.phys.ens.fr/∼zamponi

  1. T.R.Kirkpatrick and P. G. Wolynes, “Connections be-tween some kinetic and equilibrium theories of the glass transition”, Physical Review A 35, 3072 (1987).
  2. T.Maimbourg, J.Kurchan, and F.Zamponi, “Solution of the dynamics of liquids in the large-dimensional limit”, Physical Review Letters 116, 015902 (2016).
  3. C.Rainone, P.Urbani, H.Yoshino, and F.Zamponi, “Following the evolution of hard sphere glasses in in-finite dimensions under external perturbations: com-pression and shear strain”, Physical Review Letters 114, 015701 (2015).
  4. P.Charbonneau, J.Kurchan, G.Parisi, P.Urbani, F.Zamponi, “Fractal free energy landscapes in struc-tural glasses”, Nature Communications 5, 3725 (2014).
  5. G.Parisi, P.Urbani, F.Zamponi, “Theory of simple glasses”, book in preparation (Cambrige University Press).
11:00 to 11:30 -- Coffee
11:30 to 13:00 Francesco Sciortino Entropy in Self-Assembly (Lecture 2)

I will discuss the role of entropy in some of the most relevant self-assembly processes. The outline of the lectures is the following:

Introduction

  • Entropy and Translational Order: Hard Sphere Crystallisation [1]
  • Entropy and Orientational Order: Transition [2]
  • Entropy Attracts: Depletion Interactions [3]
  • Entropy Attracts: tions [4]
  • Competition between energy and entropy in self-assembly [5]
  • Entropy and flexibility in networks [6]

Corresponding author: francesco.sciortino@uniroma1.it

  1. B. Alder and T. Wainwright, The Journal of chemical physics 27, 1208 (1957).
  2. L. Onsager, Annals of the New York Academy of Sci-ences 51, 627 (1949).
  3. H. N. Lekkerkerker and R. Tuinier, Colloids and the depletion interaction, Vol. 833 (Springer, 2011).
  4. A. Zilman, J. Kieffer, F. Molino, G. Porte, and S. Safran, Physical review letters 91, 015901 (2003).
  5. F. Sciortino, Soft Matter Self-Assembly, Varenna School, Italian Physical Society 193, 1 (2016).
  6. F. Smallenburg and F. Sciortino, Nature Physics 9, 554 (2013).
13:00 to 14:30 -- Lunch
14:30 to 16:00 Patrick Charbonneau Bridging between mean-field and real glasses (Lecture 1)

Recent years have seen remarkable advances in the mean-field theory of glasses. But do these theoretical predictions actually explain the behavior of real physi- cal systems? In these lectures, we will study this ques- tion using numerical and theoretical tools that allow to systematically interpolate between one limit [1] and the other. By tuning spatial dimension or the inter- action range between particles, we can indeed identify theoretically robust features and physical phenomena that fall beyond the mean-field scenario.

In these lectures, I will build on the material presented in previous and parallel lectures, especially the basics of liquid state theory and the mean-field theory of glasses. While L. Berthier’s lectures will mostly fo- cus on the properties of glassy states, mine will center on the dynamical slowdown of an (metastable) equi- librium liquid. More specifically, I will explore the following topics.

  1. The mechanics, advantages and challenges of running numerical simulations in higher dimen-sions [2–5].
  2. The theoretical expectations for finite-dimensional systems from RFOT [6].
  3. The theoretical and numerical results for the Mari-Kurchan (MK) model [5, 7–9].
  4. The lessons from the MK model for going be-yond → ∞ mean-field, especially from insights void percolation and random Lorentz gas [10–12].

I thank warmly all my collaborators in this extended scientific effort. The last couple of years of this re- search program were supported by a grant from the Simons Foundation (No. 454937).

Corresponding author: https://chem.duke.edu/labs/charbonneau

  1. P. Charbonneau, J. Kurchan, G. Parisi, P. Urbani, and F. Zamponi, Ann. Rev. Condens. Matter Phys. 8, 265 (2017).
  2. P. Charbonneau, A. Ikeda, G. Parisi, and F. Zam-poni, Phys. Rev. Lett. 107, 185702 (2011).
  3. B. Charbonneau, P. Charbonneau, and G. Tarjus, Phys. Rev. Lett. 108, 035701 (2012).
  4. B. Charbonneau, P. Charbonneau, Y. Jin, G. Parisi, and F. Zamponi, J. Chem. Phys. 139, 164502 (2013).
  5. P. Charbonneau, Y. Jin, G. Parisi, and F. Zamponi, Proc. Nat. Acad. Sci. U.S.A. 111, 15025 (2014).
  6. L. Berthier and G. Biroli, Rev. Mod. Phys. 83, 587 (2011).
  7. R. Mari, F. Krzakala, and J. Kurchan, Phys. Rev. Lett. 103, 025701 (2009).
  8. R. Mari and J. Kurchan, J. Chem. Phys. 135, 124504 (2011).
  9. M. Mézard, G. Parisi, M. Tarzia, and F. Zamponi, J. Stat. Mech. 2011, P03002 (2011).
  10. F. Hoefling, T. Franosch, and E. Frey, Phys. Rev. Lett. 96, 165901 (2006).
  11. T. Bauer, F. Hfling, T. Munk, E. Frey, and T. Fra-nosch, Eur. Phys. J. 189, 103 (2010).
  12. Y. Jin and P. Charbonneau, Phys. Rev. E 91, 042313 (2015).
16:00 to 18:00 Susan Coppersmith From bits to qubits: a quantum leap for computers (ICTS Distinguished Lecture)

The steady increase in computational power of information processors over the past half-century has led to smart phones and the internet, changing commerce and our social lives. Up to now, the primary way that computational power has increased is that the electronic components have been made smaller and smaller, but within the next decade feature sizes are expected to reach the fundamental limits imposed by the size of atoms. However, it is possible that further huge increases in computational power could be achieved by building quantum computers, which exploit in new ways of the laws of quantum mechanics that govern the physical world. This talk will discuss the challenges involved in building a large-scale quantum computer as well as progress that we have made in developing a quantum computer using silicon quantum dots, some of which is enabled by concepts developed in the context of statistical physics and nonlinear dynamics. Prospects for further development will also be discussed. 

Thursday, 27 September 2018
Time Speaker Title Resources
09:30 to 11:00 Francesco Zamponi Mean field theory of the glass transition (Lecture 3)

The development of a mean field theory of glasses started in the 80s, through the work of Kirkpatrick, Thirumalai and Wolynes. They identified a class of mean field spin glass models, whose qualitative behav- ior is very similar to the one of supercooled liquid and glasses measured in the laboratory. They proposed that these spin glass models could serve as represen- tative of a broad universality class, called the Ran- dom First Order Transition (RFOT) class, in which the glass transition would fall, at least at the mean field level. To substantiate this claim, they proposed that a system of d-dimensional interacting particles would fall in this class in the d → ∞ limit [1].

During the subsequent two decades, a lot of work has been done on RFOT spin glass models, which provided many important predictions on the thermodynamics and dynamics of RFOT systems: glass transition, aging, effective temperatures, complexity, dynamical heterogeneities... However, proving that the original conjecture of [1] is correct took another decade, and the program was completed in the last few years.

In these lectures I will review the solution of parti- cle systems in d → ∞. I will show that the behavior is precisely the one of the RFOT universality class. I will start by the study of the equilibrium dynamics and show the existence of a dynamical glass transition similar to the one of Mode-Coupling Theory [2]. Next, I will show how the long time limit of the dynamics in the glass phase can be studied via the replica method using the “state following” or Franz-Parisi construc- tion [3]. Finally, I will briefly discuss the Gardner and jamming transitions [4].

During the lectures, physical concepts such as the dy- namical glass transition, the complexity, the Kauz- mann transition, the out-of-equilibrium glass state, and the criticality of jamming will be discussed. Methodologically, we will introduce dynamical and replica techniques. The lectures are based on a book which is currently being written [5].

Corresponding author: www.phys.ens.fr/∼zamponi

  1. T.R.Kirkpatrick and P. G. Wolynes, “Connections be-tween some kinetic and equilibrium theories of the glass transition”, Physical Review A 35, 3072 (1987).
  2. T.Maimbourg, J.Kurchan, and F.Zamponi, “Solution of the dynamics of liquids in the large-dimensional limit”, Physical Review Letters 116, 015902 (2016).
  3. C.Rainone, P.Urbani, H.Yoshino, and F.Zamponi, “Following the evolution of hard sphere glasses in in-finite dimensions under external perturbations: com-pression and shear strain”, Physical Review Letters 114, 015701 (2015).
  4. P.Charbonneau, J.Kurchan, G.Parisi, P.Urbani, F.Zamponi, “Fractal free energy landscapes in struc-tural glasses”, Nature Communications 5, 3725 (2014).
  5. G.Parisi, P.Urbani, F.Zamponi, “Theory of simple glasses”, book in preparation (Cambrige University Press).
11:00 to 11:30 -- Coffee
11:30 to 13:00 Ludovic Berthier Measuring the configurational entropy in computer simulations of deeply supercooled liquids (Lecture 2)

In these lectures, I will employ the material presented in the introductory lectures, in particular the basics of liquid state theory and statistical mechanics to explain how the configurational entropy of supercooled liquids can be measured in computer simulations of supercooled liquids [1].

I will first explain why we must care about the configurational entropy, how it is defined and what are the conceptual problems associated to this important quantity, from the ill-defined concept of thermodynamic metastability to issues related to polydisperse liquid models.

I will then talk about computer simulations of super- cooled liquids, how they are done, and what can be hoped to be achieved using this important tool. In particular, I will emphasize the new opportunities offered by the recent development of the SWAP algorithm [2] to explore more ambitiously than before the thermodynamic properties of deeply supercooled liquids [3].

Then I will show how in practice one defines and mea- sures using computer simulations various proxies for the configurational entropy, from the potential energy landscape approach, from the Frenkel-Ladd thermodynamic construction, from the Franz-Parisi free energy, and from the point-to-set correlation length measurement.

These lectures have strong connections with the mean- field results presented in the parallel lectures by F. Zamponi and J. Kurchan.

Corresponding author: ludovic.berthier@umontpellier.fr

L. Berthier and G. Biroli, Theoretical perspective on the glass transition and amorphous materials, Rev. Mod. Phys. 83, 587 (2011).
A. Ninarello, L. Berthier, and D. Coslovich, Models and algorithms for the next generation of glass transition studies, Phys. Rev. X 7, 021039 (2017).
L. Berthier, P. Charbonneau, D. Coslovich, A. Ninarello, M. Ozawa, and S. Yaida, Configurational entropy measurements in extremely supercooled liquids that break the glass ceiling, Proc. Natl. Acad. Sci U. S. A. 114, 11356 (2017).

13:00 to 14:30 -- Lunch
14:30 to 16:00 Patrick Charbonneau Bridging between mean-field and real glasses (Lecture 2)

Recent years have seen remarkable advances in the mean-field theory of glasses. But do these theoretical predictions actually explain the behavior of real physi- cal systems? In these lectures, we will study this ques- tion using numerical and theoretical tools that allow to systematically interpolate between one limit [1] and the other. By tuning spatial dimension or the inter- action range between particles, we can indeed identify theoretically robust features and physical phenomena that fall beyond the mean-field scenario.

In these lectures, I will build on the material presented in previous and parallel lectures, especially the basics of liquid state theory and the mean-field theory of glasses. While L. Berthier’s lectures will mostly fo- cus on the properties of glassy states, mine will center on the dynamical slowdown of an (metastable) equi- librium liquid. More specifically, I will explore the following topics.

  1. The mechanics, advantages and challenges of running numerical simulations in higher dimen-sions [2–5].
  2. The theoretical expectations for finite-dimensional systems from RFOT [6].
  3. The theoretical and numerical results for the Mari-Kurchan (MK) model [5, 7–9].
  4. The lessons from the MK model for going be-yond → ∞ mean-field, especially from insights void percolation and random Lorentz gas [10–12].

I thank warmly all my collaborators in this extended scientific effort. The last couple of years of this re- search program were supported by a grant from the Simons Foundation (No. 454937).

Corresponding author: https://chem.duke.edu/labs/charbonneau

  1. P. Charbonneau, J. Kurchan, G. Parisi, P. Urbani, and F. Zamponi, Ann. Rev. Condens. Matter Phys. 8, 265 (2017).
  2. P. Charbonneau, A. Ikeda, G. Parisi, and F. Zam-poni, Phys. Rev. Lett. 107, 185702 (2011).
  3. B. Charbonneau, P. Charbonneau, and G. Tarjus, Phys. Rev. Lett. 108, 035701 (2012).
  4. B. Charbonneau, P. Charbonneau, Y. Jin, G. Parisi, and F. Zamponi, J. Chem. Phys. 139, 164502 (2013).
  5. P. Charbonneau, Y. Jin, G. Parisi, and F. Zamponi, Proc. Nat. Acad. Sci. U.S.A. 111, 15025 (2014).
  6. L. Berthier and G. Biroli, Rev. Mod. Phys. 83, 587 (2011).
  7. R. Mari, F. Krzakala, and J. Kurchan, Phys. Rev. Lett. 103, 025701 (2009).
  8. R. Mari and J. Kurchan, J. Chem. Phys. 135, 124504 (2011).
  9. M. Mézard, G. Parisi, M. Tarzia, and F. Zamponi, J. Stat. Mech. 2011, P03002 (2011).
  10. F. Hoefling, T. Franosch, and E. Frey, Phys. Rev. Lett. 96, 165901 (2006).
  11. T. Bauer, F. Hfling, T. Munk, E. Frey, and T. Fra-nosch, Eur. Phys. J. 189, 103 (2010).
  12. Y. Jin and P. Charbonneau, Phys. Rev. E 91, 042313 (2015).
15:30 to 16:00 -- Coffee
16:30 to 17:30 -- Tutorial
Friday, 28 September 2018
Time Speaker Title Resources
09:30 to 11:00 Ludovic Berthier Measuring the configurational entropy in computer simulations of deeply supercooled liquids (Lecture 3)

In these lectures, I will employ the material presented in the introductory lectures, in particular the basics of liquid state theory and statistical mechanics to explain how the configurational entropy of supercooled liquids can be measured in computer simulations of supercooled liquids [1].

I will first explain why we must care about the configurational entropy, how it is defined and what are the conceptual problems associated to this important quantity, from the ill-defined concept of thermodynamic metastability to issues related to polydisperse liquid models.

I will then talk about computer simulations of super- cooled liquids, how they are done, and what can be hoped to be achieved using this important tool. In particular, I will emphasize the new opportunities offered by the recent development of the SWAP algorithm [2] to explore more ambitiously than before the thermodynamic properties of deeply supercooled liquids [3].

Then I will show how in practice one defines and mea- sures using computer simulations various proxies for the configurational entropy, from the potential energy landscape approach, from the Frenkel-Ladd thermodynamic construction, from the Franz-Parisi free energy, and from the point-to-set correlation length measurement.

These lectures have strong connections with the mean- field results presented in the parallel lectures by F. Zamponi and J. Kurchan.

Corresponding author: ludovic.berthier@umontpellier.fr

L. Berthier and G. Biroli, Theoretical perspective on the glass transition and amorphous materials, Rev. Mod. Phys. 83, 587 (2011).
A. Ninarello, L. Berthier, and D. Coslovich, Models and algorithms for the next generation of glass transition studies, Phys. Rev. X 7, 021039 (2017).
L. Berthier, P. Charbonneau, D. Coslovich, A. Ninarello, M. Ozawa, and S. Yaida, Configurational entropy measurements in extremely supercooled liquids that break the glass ceiling, Proc. Natl. Acad. Sci U. S. A. 114, 11356 (2017).

11:00 to 11:30 -- Coffee
11:30 to 13:00 Patrick Charbonneau Bridging between mean-field and real glasses (Lecture 3)

Recent years have seen remarkable advances in the mean-field theory of glasses. But do these theoretical predictions actually explain the behavior of real physi- cal systems? In these lectures, we will study this ques- tion using numerical and theoretical tools that allow to systematically interpolate between one limit [1] and the other. By tuning spatial dimension or the inter- action range between particles, we can indeed identify theoretically robust features and physical phenomena that fall beyond the mean-field scenario.

In these lectures, I will build on the material presented in previous and parallel lectures, especially the basics of liquid state theory and the mean-field theory of glasses. While L. Berthier’s lectures will mostly fo- cus on the properties of glassy states, mine will center on the dynamical slowdown of an (metastable) equi- librium liquid. More specifically, I will explore the following topics.

  1. The mechanics, advantages and challenges of running numerical simulations in higher dimen-sions [2–5].
  2. The theoretical expectations for finite-dimensional systems from RFOT [6].
  3. The theoretical and numerical results for the Mari-Kurchan (MK) model [5, 7–9].
  4. The lessons from the MK model for going be-yond → ∞ mean-field, especially from insights void percolation and random Lorentz gas [10–12].

I thank warmly all my collaborators in this extended scientific effort. The last couple of years of this re- search program were supported by a grant from the Simons Foundation (No. 454937).

Corresponding author: https://chem.duke.edu/labs/charbonneau

  1. P. Charbonneau, J. Kurchan, G. Parisi, P. Urbani, and F. Zamponi, Ann. Rev. Condens. Matter Phys. 8, 265 (2017).
  2. P. Charbonneau, A. Ikeda, G. Parisi, and F. Zam-poni, Phys. Rev. Lett. 107, 185702 (2011).
  3. B. Charbonneau, P. Charbonneau, and G. Tarjus, Phys. Rev. Lett. 108, 035701 (2012).
  4. B. Charbonneau, P. Charbonneau, Y. Jin, G. Parisi, and F. Zamponi, J. Chem. Phys. 139, 164502 (2013).
  5. P. Charbonneau, Y. Jin, G. Parisi, and F. Zamponi, Proc. Nat. Acad. Sci. U.S.A. 111, 15025 (2014).
  6. L. Berthier and G. Biroli, Rev. Mod. Phys. 83, 587 (2011).
  7. R. Mari, F. Krzakala, and J. Kurchan, Phys. Rev. Lett. 103, 025701 (2009).
  8. R. Mari and J. Kurchan, J. Chem. Phys. 135, 124504 (2011).
  9. M. Mézard, G. Parisi, M. Tarzia, and F. Zamponi, J. Stat. Mech. 2011, P03002 (2011).
  10. F. Hoefling, T. Franosch, and E. Frey, Phys. Rev. Lett. 96, 165901 (2006).
  11. T. Bauer, F. Hfling, T. Munk, E. Frey, and T. Fra-nosch, Eur. Phys. J. 189, 103 (2010).
  12. Y. Jin and P. Charbonneau, Phys. Rev. E 91, 042313 (2015).
13:00 to 14:30 -- Lunch
14:30 to 16:00 Francesco Sciortino Entropy in Self-Assembly (Lecture 3)

I will discuss the role of entropy in some of the most relevant self-assembly processes. The outline of the lectures is the following:

Introduction

  • Entropy and Translational Order: Hard Sphere Crystallisation [1]
  • Entropy and Orientational Order: Transition [2]
  • Entropy Attracts: Depletion Interactions [3]
  • Entropy Attracts: tions [4]
  • Competition between energy and entropy in self-assembly [5]
  • Entropy and flexibility in networks [6]

Corresponding author: francesco.sciortino@uniroma1.it

  1. B. Alder and T. Wainwright, The Journal of chemical physics 27, 1208 (1957).
  2. L. Onsager, Annals of the New York Academy of Sci-ences 51, 627 (1949).
  3. H. N. Lekkerkerker and R. Tuinier, Colloids and the depletion interaction, Vol. 833 (Springer, 2011).
  4. A. Zilman, J. Kieffer, F. Molino, G. Porte, and S. Safran, Physical review letters 91, 015901 (2003).
  5. F. Sciortino, Soft Matter Self-Assembly, Varenna School, Italian Physical Society 193, 1 (2016).
  6. F. Smallenburg and F. Sciortino, Nature Physics 9, 554 (2013).
15:30 to 16:00 -- Coffee
16:30 to 17:30 -- Tutorial
Monday, 01 October 2018
Time Speaker Title Resources
09:30 to 11:00 Magdaleno Medina-Noyola Non-equilibrium Kinetics of the Transformation of Liquids into Physical Gels

J. M. Olais-Govea, L. Lopez-Flores, and M. Medina-Noyola

A major stumbling block for statistical physics and materials science has been the lack of a universal principle that allows us to understand and predict elementary structural, morphological, and dynamical properties of non-equilibrium amorphous states of matter. The recently-developed non-equilibrium self-consistent generalized Langevin equation (NE-SCGLE) theory, however, has been shown to provide a fundamental tool for the understanding of the most essential features of the transformation of liquids into amorphous solids, such as their aging kinetics or their dependence on the protocol of fabrication. In this work we focus on the predicted kinetics of one of the main fingerprints of the formation of gels by arrested spinodal decomposition of suddenly and deeply quenched simple liquids, namely, the arrest of structural parameters associated with the morphological evolution from the initially uniform fluid, to the dynamically arrested sponge-like amorphous material. The comparison o f the theoretical predictions with simulation and experimental data measured on similar but more complex materials, suggests the universality of the predicted scenario.

11:00 to 11:30 -- Coffee
11:30 to 13:00 Remi Monasson Phase transitions in high-dimensional statistical inference (Lecture 1)

Lecture 1: High-Dimensional Inference: Basic techniques

  1. Bayesian inference
  2. Principal Component Analysis (PCA)
  3. Spiked covariance model and retarded learning phase transition
  4. Role of prior information

References:

  1. Information theory, inference, learning algorithms
    David MacKay, Cambridge University Press
  2. http://www.inference.org.uk/itila/book.html
  3. Introduction to the theory of neural computation
    John Hertz, Andreas Hertz, Richard Palmer, Santa Fe Institute series
  4. Statistical physics and representations in real and artificial neural networks
    Simona Cocco, Remi Monasson, Lorenzo Posani, Sophie Rosay, Jerome Tubiana, Physica A (2018)
    https://arxiv.org/abs/1709.02470
  5. Inverse statistical physics of protein sequences: a key issues review
    Simona Cocco, Christoph Feinauer, Matteo Figliuzzi, Remi Monasson, Martin Weigt, Rep. Phys. Prog. (2018)
    http://www.phys.ens.fr/~monasson/Articles/a107.pdf
13:00 to 14:30 -- Lunch
14:30 to 15:30 Amit Ghosal Glassy behavior associated with melting of two-dimensional Coulomb clusters

We present responses of a small number of Coulomb-interacting particles in two-dimensional confinements, across the crossover from their solid- to liquid-like behaviors. Here, irregular confinements emulate the role of disorder.

Focusing first on the thermal melting, where zero-point motion of the particles are frozen, we explore the signatures of a 'hexatic-glass' like behavior. While static correlations, which investigate the translational and bond orientational order [1,2], indicate a hexatic-like phase at low temperatures, dynamical correlations show considerably slow relaxations. Using density correlations we probe intriguing inhomogeneities arising from the interplay of the irregularity in the confinement and long-range interactions. The relaxation at multiple time scales show stretched-exponential decay of spatial correlations for Coulomb-particles in irregular traps [1,3]. Temperature dependence of characteristic time scales, depicting the structural relaxation of the system, show strong similarities with those observed for the glassy systems. Our results indicate that some of the key features of supercooled liquids emerge in confined systems. more so with irregular confinements. The analysis of normal modes [4] elucidates how long time behavior of the system is encoded in the quasi-localized modes.

Time permitting, we extend our discussions to include the effects of quantum fluctuations. Our results, using quantum Monte Carlo techniques for Boltzmann particles, seem to indicate complementary mechanism for the quantum and thermal crossovers in Wigner molecules [5]. We will also discuss our recent analyses upon including the effects of quantum statistics.

  1. B. Ash, J. Chakrabarti and A. Ghosal, Phys. Rev. E 96, 042105 (2017).
  2. D. Bhattacharya and A. Ghosal, Eur. Phys. J. B 86, 499 (2013).
  3. B. Ash, J. Chakrabarti and A. Ghosal, Euro. Phys. Lett., 114, 4, (2016).
  4. B. Ash, C. Dasgupta and A. Ghosal, To appear in Phys. Rev. E (2018) (arXiv:1805.11180).
  5. D. Bhattacharya, A. V. Filinov, A. Ghosal and M.Bonitz, Eur. Phys. J. B 89, 60, (2016).
15:30 to 16:00 -- Coffee
16:30 to 17:30 -- Tutorial
Wednesday, 03 October 2018
Time Speaker Title Resources
09:30 to 11:00 Remi Monasson Phase transitions in high-dimensional statistical inference (Lecture 2)

High-Dimensional Inference: Unsupervised Learning with Neural Networks

  1. What is Unsupervised learning?
  2. Autoencoders and connection with PCA
  3. Boltzmann machines and Restricted Boltzmann machines
11:00 to 11:30 -- Coffee
11:30 to 13:00 Mahesh M Bandi Applying Higher-order Turbulence Spectra from Energy to UAV

Kolmogorov’s 1941 theory elucidating the spectrum of turbulent velocity fluctuations forms the cornerstone of contemporary turbulence research. This result requires one to measure the velocity everywhere within the turbulent flow at the same time instant. However, many situations exist where measurements are needed over time at one or few fixed spatial (Eulerian) locations, sometimes involving not velocity but its higher powers. The physical interpretation of such measurements strongly diverges from the Kolmogorov framework. In this talk, I will review the revised theoretical framework and support it with evidence from our experiments in two and three dimensional flows. I will then explain how this revised framework provides a toolkit to address a diverse range of questions in Energy, UAV mechanics, Environmental Sciences, and perhaps even Life Sciences.

13:00 to 14:30 -- Lunch
14:30 to 16:00 Remi Monasson Phase transitions in high-dimensional statistical inference (Lecture 3)

High-Dimension Inference: Application to protein modeling

  1. Biological motivations
  2. Methods
  3. Results

References:

  1. Information theory, inference, learning algorithms
    David MacKay, Cambridge University Press
  2. Link
  3. Introduction to the theory of neural computation
    John Hertz, Andreas Hertz, Richard Palmer, Santa Fe Institute series
  4. Statistical physics and representations in real and artificial neural networks
    Simona Cocco, Remi Monasson, Lorenzo Posani, Sophie Rosay, Jerome Tubiana, Physica A (2018)
    Link
  5. Inverse statistical physics of protein sequences: a key issues review
    Simona Cocco, Christoph Feinauer, Matteo Figliuzzi, Remi Monasson, Martin Weigt, Rep. Phys. Prog. (2018)
    Link
15:30 to 16:00 -- Coffee
16:30 to 17:30 Remi Monasson Phase transitions in high-dimensional statistical inference (Lecture 4)
Thursday, 04 October 2018
Time Speaker Title Resources
10:30 to 11:00 -- Coffee
11:00 to 12:00 Stephan Herminghaus Artificial microswimmers: individual and collective phenomena

Plankton provides the most important route of injection of solar energy into the biosystem. It is therefore of major importance to attain a deep understanding of swimming motility and swarming of these microorganisms. As their natural habitats include turbulent (oceanic photosphere) and still (lacustrine) waters as well as the benthic (seafloor) areas, a wide variety of geometries and flow conditions are to be studied. We discuss a number of phenomena found recently in both natural single-cell swimmers (Chlamydomonas reinhartii) and artificial liquid microswimmers consisting of self-propelling 'oil' droplets. Some emphasis is given to properties which may be relevant for biofilm formation, such as adhesion and swarm formation, in particular in non-trivial geometries.

13:00 to 14:30 -- Lunch
Friday, 05 October 2018
Time Speaker Title Resources
10:30 to 11:00 -- Coffee
11:00 to 12:00 Vijay Kumar Krishnamurthy Interacting active particles: single-file diffusion and fluctuation-induced forces

Active-Brownian-particles (ABPs) and run-and-tumble particles (RTPs) are minimal realizations of scalar active matter. We will start by discussing exact solutions for non-interacting RTPs in 1D in both unconfined and confined geometries. We will then move on to discuss single-file-diffusion in a system of interacting RTPs in 1D and show that the MSD of a tagged particle displays scaling behavior with the density and activity with an asymptotic t1/2 dependence on time. This is true also for ABPs confined in a narrow annular channel. We will then present our preliminary experimental results on interacting ABPs, realized as isotropic self-propelled disks on a vibrated granular shaker, and demonstrate that various statistical quantities compare favourably with simulations. Finally, we will discuss fluctuation-induced interactions between anisotropic inclusions in a nonequilibrium heat-bath composed of interacting ABPs.

13:00 to 14:30 -- Lunch
Monday, 08 October 2018
Time Speaker Title Resources
11:10 to 12:30 Samriddhi Sankar Ray Turbulent Transport: Beyond Spherical Particles

We present recent results on non-spherical particles and elastic fibers in a turbulent flow. In particular, we discuss the issue of preferential sampling of flows by such "particles" with internal degrees of freedom and compare them with the more standard spherical particle approach. If time permits, we will present recent results on the emergence of collective motion for active rods and disks in fully developed turbulence.

Tuesday, 09 October 2018
Time Speaker Title Resources
11:10 to 12:30 Muhittin Mungan AQS-automata, state transition graphs, return-point memory and random maps

AQS-automata arise naturally in the description of the athermal dynamics of a disordered system -- such as spin glasses -- when a slowly changing uniform driving force is applied. The response of such systems is characterized by abrupt transitions between quasi-static configurations which are generally irreversible, giving thus rise to hysteresis. The dynamical response of such systems can be described in terms of a pair of random, directed and acyclic graphs, capturing the transitions triggered by force increases and decreases, respectively. Properties such as return-point memory emerge then as features of these graphs. In this talk I will develop the graph-theoretic description of AQS-automata and then present recent work with T. Witten on modelling the AQS dynamics by random maps.

Wednesday, 10 October 2018
Time Speaker Title Resources
11:10 to 12:30 Kapilanjan Krishnan The Physics of Beauty – A hairy story

The perception of beauty is strongly linked to order and symmetry. These perceptions engraved into our evolutionary psychology as we survive by being the fittest. However, quantifying these perceptions, and the technical truth underlying them has many challenges, some of which will be shared in the context of hair. Two specific problems are (1) the dynamics of the tangling/detangling of hair, and (2) the movement of hair. Getting stronger analytical insights on the impact of microscale material parameters against macroscopic variations in the amount of structural disorder or momentum distributions would help design products for consumers.

Thursday, 11 October 2018
Time Speaker Title Resources
11:10 to 12:30 Rituparno Mandal Extreme Active Matter at High Densities

Extreme active matter, comprising self-propelled particles characterised by large persistence time \tau_p and high Péclet number, exhibits remarkable behaviour at high densities. As \tau_p → 0, the material undergoes a conventional fluid-to-glass transition via density relaxation, as one reduces the active propulsion force f . In the other limit, \tau_p → ∞, the fluid jams at a critical point on lowering f to f^∗ (∞), with stresses concentrated along force-chains. In between these limits, the approach to dynamical arrest at low f , goes through a phase characterised by intermittency in the kinetic and potential energy. This intermittency is a consequence of long periods of jamming followed by bursts of plastic yielding associated with Eshelby deformations, akin to the response of dense amorphous solids to an externally imposed shear. In the vicinity of the intermittency-fluid phase boundary, correlated plastic events result in large scale vorticity and turbulence. Dense extreme active matter brings together the physics of glass, jamming, plasticity and turbulence, in a new state of driven classical matter.

Friday, 12 October 2018
Time Speaker Title Resources
11:10 to 12:30 -- Discussions
Monday, 15 October 2018
Time Speaker Title Resources
15:00 to 16:00 Surajit Sengupta Solid rigidity: A thermodynamic origin story

School textbooks tell us that the main difference between a solid and a liquid is the ability of the former to retain its shape. Any attempt at changing the shape of a solid is resisted by an internal elastic stress unless the deformation crosses a limiting value; at which point the solid fails. This naive viewpoint, although of great practical value, is, however, fundamentally incorrect. For example, one can argue that given enough time, atoms in the solid can always rearrange to eliminate stress no matter how much, or how little, the solid is deformed. Resolution of this paradoxical result lies at the core of our understanding of the behavior of solids under deformation. Adapting ideas which were introduced recently to study glasses, we find that rigidity arises a result of a hidden first-order phase transition between phases which differ in the way they respond to changes of shape [1]. When deformed by any amount, howsoever small, the rigid solid goes into a meta-stable state analogous to superheated water. Eventually, this meta-stable state always decays by nucleating bubbles of the stable, stress-free, solid by a process very similar to how bubbles of steam appear in a kettle of boiling water. This fresh conceptual viewpoint curiously allows us to study failure of perfect crystalline solids in quantitative detail without invoking specifics of many-body, defect–defect interactions, raising hope of a more unified description of materials in the future.

[1] Nath et al. PNAS 115 E4322-E4329 (2018)

16:30 to 17:30 -- Discussion
Tuesday, 16 October 2018
Time Speaker Title Resources
11:10 to 12:00 Hisao Hayakawa The characterization of dense jammed matter: mutual relationships among the shear-jammed, fragile states and the discontinuous shear thickening

The mechanical response of two-dimensional frictional granular materials under an oscillatory shear in a constant volume are numerically investigated. It is confirmed that the shear storage modulus G′ depends on the initial amplitude of the oscillation to prepare the system before the measurement. For sufficiently large initial strain amplitude, the shear jammed state satisfying G′ > 0 is observed even if the packing fraction is below the jamming point. The fragile state is also identified as a long lived metastable state where G′ depends on the phase of the oscillatory shear. The dynamic viscosity evaluated from the shear loss modulus G′′ exhibits a sudden jump similar to the discontinuous shear thickening in the fragile state. In this talk we also show some preliminary results of hydrodynamic simulation for colloidal suspensions to discuss shear jamming and DST as well as the behavior of dry granular particles under the pressure control protocol.

Wednesday, 17 October 2018
Time Speaker Title Resources
11:10 to 12:00 Srikanth Sastry Yielding in amorphous solids

The loss of rigidity in amorphous solids when subjected to external stress has been investigated actively in recent years. I will describe recent results regarding the nature of the yielding transition, including strain localisation in the yielded solid, annealing effects below and above the yielding threshold, obtained by computational investigations of amorphous solids subjected to oscillatory deformation.

Monday, 22 October 2018
Time Speaker Title Resources
11:10 to 12:30 Subir Das Phase Transitions: Diversity in dynamics

Following a general discussion on universalities related to various structural and dynamical aspects of phase transitions, I will concentrate on nonequilibrium phenomena. In this domain a set of problems will be described with the objective of highlighting how various aspects of coarsening phenomena depend upon space dimension, morphology, etc. Finally, I will present results from two problems of my current interest. One is related to kinetics of vapor-solid transitions and the other deals with the ordering in popular Ising ferromagnet. The aim will be to project the breadth of diversity even in simple situations.

Tuesday, 23 October 2018
Time Speaker Title Resources
11:10 to 12:30 Subhro Battacharjee Butterfly effect in classical spin systems

Connections between many-body chaos and ergodicity form the basis of statistical mechanics. Starting with an overview of recent interests in this area, I shall discuss our numerical results characterising spatio-temporal signatures of chaos in spin systems and point out their possible quantitative connection to measures of transport such as diffusion coefficients. I shall discuss how the physics of frustration in classical spin systems help retain the signatures of chaos even at low temperatures.

Wednesday, 24 October 2018
Time Speaker Title Resources
11:10 to 12:30 Smarajit Karmakar Growth of Order and its role in the Dynamics of Supercooled Liquids

Existence and growth of amorphous and other structural order in supercooled liquids approaching glass transition is a subject of intense research. Even after decades of work, there is still no clear consensus on the molecular mechanisms that lead to a rapid slowing down of liquid dynamics approaching this putative transition. The existence of a correlation length associated with amorphous order has recently been postulated and also been estimated using multi-point correlation functions which cannot be calculated easily in experiments. Thus the study of growing amorphous order remains mostly restricted to systems like colloidal glasses and simulations of model glass-forming liquids. We proposed an experimentally realizable yet simple correlation function to study the growth of amorphous order. We then demonstrate the validity of this approach for a few well-studied model supercooled liquids and obtain results, which are consistent with other conventional methods. Finally I will discuss role of the static length-scale associated with this amorphous order in dynamics of glassy systems with medium range crystalline order. We tried to understand the molecular mechanisms for glass transition in liquids with and without medium range crystalline order. The issue is important to answer because if the liquid eventually starts to form crystalline domains while approaching the glass transition then the complexity of the problem may simplify and may just be governed by the physics of the growing crystalline order. If not then there exists a new class of glass forming materials whose molecular mechanism for slowing down of dynamics will probably be easier to understand in terms of the dynamics of the growing medium range crystalline order. We found evidence that dynamics of glasses with medium range crystalline order are generically different from other glass forming liquids with no predominant local order. 

Reference:

1. R Das, S Chakrabarty and S Karmakar, Soft Matter 13, 6929 (2017).

2. S Chakrabarty, I Tah, S Karmakar and C Dasgupta, PRL 119, 205502 (2017).

3. I Tah, S Sengupta, S Sastry, C Dasgupta and S Karmakar, PRL 121, 085703 (2018).

4. BP Bhowmik, I Tah and S Karmakar, PRE, 98, 022122 (2018)."

Thursday, 25 October 2018
Time Speaker Title Resources
11:10 to 12:30 Pinaki Chaudhuri Response of glassy systems to quenched disorder

Understanding how quenched disorder affects the glassy behaviour of materials has been of interest, for quite some time, for example, in the context of type-II superconductors, metallic alloys etc. More recently, specific constructions in the form of pinned particles, have been used to investigate the onset of slow dynamics and exploring the ideal glass transition scenario. In this context, using numerical studies, we will discuss two different situations : (a) the interplay of a simple glass forming liquid with a spatially-varying external potential, motivated by recent optical realisations & (b) yielding dynamics of a glass embedded with impurities.

Friday, 26 October 2018
Time Speaker Title Resources
11:10 to 12:30 Meher Prakash Mutual information for protein structure and dynamics

Though the physical laws at the atomic level interactions of amino acids in proteins are well defined and simple, understanding how proteins work is non-trivial. Protein sequence -> structure -> dynamics is believed to be the key to the hierarchy of their functional organization. There are several gaps in this perspective which are being filled with informatic methods these days. For example, using large scale evolutionary data of sequences to predict the structure or to derive relationship with dynamics. One of the commonly used tools for this purpose is mutual information. The lecture will cover the basics of this informatic method as well as its implications to the understanding of proteins.