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Wednesday, 15 December 2021
Time Speaker Title Resources
14:00 to 15:00 Chandan Dasgupta (ICTS-TIFR, India) Replica Symmetry Breaking in Spin Glasses

Replica symmetry breaking in mean-field models of spin glasses is probably the most well-known work of Giorgio Parisi. I will present a pedagogical account of replica symmetry breaking in the Parisi solution for the equilibrium properties of an infinite-range  model of Ising spin glass and discuss subsequent developments.

15:00 to 16:00 Enzo Marinari (Sapienza University, Italy) The History, The Power and the Perspectives of Numerical Simulations of Spin Glasses.

Numerical simulations have played and are playing a crucial role in the arena of finite dimensional spin glasses, where many crucial issues are still waiting, after more than 40 years, for being better understood. I will start with an historical perspective, discussing why optimized algorithms are needed for a numerical understanding of spin glasses.  I will discuss the difference of the static, equilibrium point of view versus the reproduction of the dynamical behavior of the system. I will also discuss the issue of computing correlation lengths
both in numerical simulations and in experiments, analyzing two very related papers, one numerical and the other experimental, that have had a strong impact on very recent results. After stressing the importance that optimized and dedicated computers have had, I will focus on recent developments, always discussing a very strict relation of new numerical results analyzed by using and introducing scaling ideas and new, connected, experimental results.

16:00 to 17:00 Break Break
17:00 to 18:00 Srikanth Sastry (JNCASR, India) The Structural Glass Transition and Replica Theory

The investigation of spin glass models, whose behavior bears similarity to the phenomenology of structural glass formers and the glass transition, has had a strong influence in the development of an understanding of the structural glass transition. Beginning as an analogy, the investigation of spin glass models provided a framework within which to organize prevailing ideas about the glass transition, as a random first order transition. Subsequent work has aimed to combine liquid state and replica theories to develop a theory of the glass transition in liquids. Salient aspects of this development will be outlined.

18:00 to 19:00 Francesco Zamponi (École Normale Supérieure, France) Recent Progresses in The Mean-Field Approach to the Jamming Transition

I will describe recent progress that has been made in a first-principle description of the jamming transition, based on the replica symmetry breaking idea. In particular, I will describe the calculation of the critical exponents.

19:00 to 20:00 Smarajit Karmakar (TIFR, Hyderabad, India) Swap Monte Carlo Method and its Enormous Impact In the Study of Structural Glasses

In this talk, I will discuss recent developments of the swap Monte Carlo method that Giorgio Parisi and Tomas Grigera proposed for enhanced sampling of the landscape in 2001. Initially, the method was not very successful and did not attract much attention from the scientific community, particularly the glass community. However, in recent years, its efficiency has been proven beyond doubt, leading to the possibility of understanding the structure of deeply supercooled states, well-known as ultra-stable glassy states. This talk will highlight how Giorgio's intuitions played a central role in achieving this impressive feat. 

Thursday, 16 December 2021
Time Speaker Title Resources
14:00 to 16:00 Giorgio Parisi (Sapienza University, Italy) Putting Order into Disorder: An Application to the Chronology of my Works

In this talk I will review the chronology of my works trying to find some logical explanation for the sequence of works I have done.

16:00 to 17:00 Break Break
17:00 to 18:00 Herbert Spohn (Technical University of Munich, Germany.) Facets of the Kardar-Parisi-Zhang equation

In 1986 Giorgio Parisi, together with M. Kardar and Y.-C. Zhang, wrote the article “Dynamic scaling of growing interfaces”. This contribution is Giorgio’s second highly cited scientific paper. Presumably one reason for such a tremendous interest is the unexpected appearance of the KPZ equation in areas remote from the originally anticipated interface dynamics. In my contribution I will cover old and more recent facets of the equation.

18:00 to 19:00 Angelo Vulpiani (Sapienza University, Italy) Multifractal Approach to Fully Developed Turbulence

The idea of the multifractals is basically contained in the large deviation theory; however, the introduction of the multifractal description in 1980s had an important role in statistical physics, chaos and disordered systems. In particular, to clarify in a rather neat way that the  usual idea, coming from critical phenomena, that just few scaling exponents are relevant, is not completely correct, and an infinite set of exponents is necessary for a complete characterization of the scaling features. I discuss the  multifractal approach  to  fully developed turbulence, in particular  some nontrivial predictions for the statistical properties of the velocity gradients, the existence of an intermediate dissipative range and Lagrangian statistics.

19:00 to 20:00 Roberto Benzi (University of Rome Tor Vergata, Italy) Stochastic Resonance in Climate Change

In this talk I will review the mechanism of stochastic resonance and in particular its relevance in paleo-climatic variability. The idea was introduced in a paper in collaboration with G. Parisi, A. Sutera and A. Vulpiani in 1982. I will discuss how the idea of stochastic resonance was born and  which were the basic physical motivations. Next I will address the main point of the paper, namely the rather unique role of the noise in the system and its cooperation with external forcing. At the time the paper was written,   this effect was entirely new  in physics not only within climate theory: nobody ever thought about this possibility. The paper by Parisi and co-workers, showed for the first time that this cooperation may occur in non linear systems like Earth climate. Later on, this cooperative effect was generalised for chaotic systems by Benzi, Sutera Vulpiani and, by now, there exist thousands of applications which exploit the mechanism of Stochastic Resonance in physics, biology and other scientific research.

Friday, 17 December 2021
Time Speaker Title Resources
14:00 to 14:30 Spenta Wadia (ICTS-TIFR, India) Planar Diagrams and Random Matrix Theory

We will summarize some of Parisi's contributions to the large N limit of quantum field theory and matrix models.

14:30 to 15:00 V. Ravindran (IMSc, India) Infrared Structure of SU(N) Gauge Theory

Higher order radiative corrections, in particular from Quantum Chromodynamics (QCD), play an important role at the Large Hadron Collider (LHC).   They also exhibit rich perturbative structure of the underlying quantum field theory. In this talk, we will discuss the universal infrared structure and the factorisation properties of on-shell scattering amplitudes and cross sections in perturbative QCD and demonstrate how they are useful to resume certain large logarithms that spoil the prediction of fixed order computations.  We present few applications in the context of inclusive and semi inclusive productions of Higgs boson and the Drell-Yan pairs at the LHC

15:00 to 16:00 Marc Mezard (ENS, France) Statistical Physics and Statistical Inference

A major challenge of contemporary statistical inference is the large-scale limit, where one wants to discover the values of many hidden parameters, using large amounts of data. In recent years, ideas from statistical physics of disordered systems, notably the cavity method, have helped to develop new algorithms for important inference problems, ranging from compressed sensing to machine learning and generalized linear regression.  The talk will review these developments and explain how they can be used, together with the replica method, to identify phase transitions in benchmark statistical ensembles of inference problems.

16:00 to 17:00 Break Break
17:00 to 18:00 Irene Giardina (Sapienza University, Italy) The Statistical Physics of Flocks and Swarms

Flocks and swarms represent iconic examples of living active matter, where motile interacting individuals give rise to emergent global patterns. Despite the great complexity of their biological components, these groups obey robust statistical laws and can be described within a statistical physics approach. In this talk I will review our current understanding of these systems.  Using experimental evidence and theoretical modelling I will show how conservation laws, interactions and motility combine together leading to non-trivial dynamics and out-of-equilibrium features on the large scale. Our analysis explains the mechanistic origin of efficient collective behaviour in living groups and unveils new challenges in the statistical physics of active systems.

18:00 to 19:00 Jorge Kurchan (ENS, France) The Replica-dynamic Correspondence in Finite Dimensions

I have recently completed the last missing link between replicas and dynamics, along the lines of a paper by Franz, Mezard Parisi and Peliti. Effective temperatures are in a one-to-one correspondence with the X parameters of Parisi's ansatz, and dynamic ultrametricity is in a one-to-one correspondence with  equilibrium ultrametricity. This correspondence, plus simple dynamic arguments, strongly suggest that time-reparametrization invariance is a central condition for the consistency of both approaches, and, furthermore, that a `sigma model'  of reparametrizations may be a promising next step to make.

19:00 to 20:00 Gilles Tarjus (Sorbonne Université, France) Supersymmetry, Dimensional Reduction and Avalanches in Random-field Models

In 1979, Parisi and Sourlas in a beautiful 2-page paper related the critical behavior of the random-field Ising model (RFIM) to a supersymmetric scalar field theory and showed that the supersymmetry (SUSY) leads to a ‘dimensional reduction’ property by which the RFIM 
behavior is identical to that of the Ising model without disorder in 2 dimensions less. It is however well established that the dimensional-reduction property breaks down in low dimensions. We relate this breakdown to the existence of scale-free avalanches in the ground state of the system at criticality and show how this long-distance physics can be described through a functional Renormalization Group. Formulating the functional RG in a superfield formalism enables us to follow the underlying SUSY and its spontaneous breaking along the RG flow and to identify a critical dimension below which dimensional reduction fails.