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Monday, 26 February 2024
Time Speaker Title Resources
09:00 to 09:20 -- Opening
09:20 to 10:00 Rahul Pandit (IISc, India) Self-gravitating bosonic and axionic systems and a minimal model for pulsar glitches

We study self-gravitating bosonic systems, candidates for dark-matter halos, by carrying out a suite of direct numerical simulations designed to investigate the formation of finite-temperature, compact objects in the three-dimensional (3D) Fourier-truncated Gross-Pitaevskii-Poisson equation (GPPE). This truncation allows us to explore the collapse and fluctuations of compact objects and show the following:

1) The statistically steady state of the GPPE, in the large-time limit and for the system sizes we study, can also be obtained efficiently by tuning the temperature in an auxiliary stochastic Ginzburg-Landau-Poisson equation.
2) Over a wide range of model parameters, this system undergoes a thermally driven first-order transition from a collapsed, compact, Bose-Einstein condensate to a tenuous Bose gas (that is not gravitationally condensed).
3) By a suitable choice of initial conditions in the GPPE, we also obtain a binary condensate that comprises a pair of collapsed objects rotating around their center of mass.
4) We use a generalised GPPE to study the collapse of an axion star.
5) By introducing a solid-crust potential and rotation in the GPPE, we develop a minimal model for pulsars and their glitches.

1. A.K. Verma, R. Pandit, and M.E. Brachet, The formation of compact objects at finite temperatures in a dark-matter-candidate self-gravitating bosonic system, Phys. Rev. Research 3 (2), L022016 (2021).
2. A.K. Verma, R. Pandit, and M.E. Brachet, Rotating self-gravitating Bose-Einstein condensates with a crust: a minimal model for pulsar glitches, Physical Review Research 4 (1), 013026 (2022).
3. S. Shukla, A.K. Verma, M.E. Brachet, and R. Pandit, Gravity- and temperature-driven phase
transitions in a model for collapsed axionic condensates, submitted for publication (November 2023).

10:00 to 10:40 Andrew Baggaley (Newcastle University, UK) Vortex Avalanches in Neutron Star Interiors

We perform large-scale 2D simulations of the Gross–Pitaevskii equation in a circular box-trap geometry with a periodic lattice of pinning sites to model nuclear lattice sites in the inner crust. By slowly spinning down the system we create localised vortex avalanches that lead to intermittent loss of the angular momentum of the superfluid. We anaylse the trajectories of vortices during these events and find evidence of collective motion of the vortices. 

10:40 to 11:10 Thibault Congy (University of Northumbria, UK) Topological Constraints on the Dynamics of Vortex Formation in a Two-Dimensional Quantum Fluid

We present experimental and theoretical results on formation of quantum vortices in a laser beam propagating in a nonlinear medium. Topological constrains richer that the mere conservation of vorticity impose an elaborate dynamical behaviour to the formation and annihilation of vortex/anti-vortex pairs. We identify two such mechanisms, both described by the same fold-Hopf bifurcation. One of them has been first proposed more than 30 years ago but had not been observed experimentally so far. The other one is new and appears particularly efficient. These results suggest new (experimentally relevant) observables for studying the transition to turbulence.
T. Congy, P. Azam, R. Kaiser, N. Pavloff, Phys. Rev. Lett. 132 033804 (2024)

11:40 to 12:20 Giacomo Roati (University of Florence, Italia) Engineering vortex matter in strongly-correlated Fermi superfluids
12:20 to 12:50 Ashton Bradley [ONLINE] (University of Otago, New Zealand) Energy damping and diffusion of quantum vortices in Bose-Einstein condensates

Dissipation mechanisms play an important role in superfluid dynamics in general, and a central role in the dynamics of high energy turbulent superfluids. While the need to understand condensate formation stimulated a solid foundation for reservoir theory of matter wave Bose-Einstein condensates, its standard incarnation - a damped Gross-Pitaevskii equation closely related to the imaginary time treatment of nonlinear ground states - fails spectacularly to describe the damping timescales of quantum vortices in experiments. I will describe an effective point vortex theory of 2D matter waves at finite temperature derived from open systems (c-field) theory in which number-conserving energy exchange with the reservoir determines the mutual friction coefficient, in agreement with experiments, and in stark contrast to the standard damped Gross-Pitaevskii treatment. Our results indicate the general significance of energy damping in cold quantum gases and we will briefly discuss implications for other systems where energy damping may be important.

14:30 to 15:00 Luca Galantucci (CNR-IAC Roma, Italia) Superfluid-driven energy and enstrophy injection in the viscous He II component

Superfluid vortex dynamics, interactions and reconnections are the fundamental elements of quantum turbulence, shaping its essential characteristics. Energy spectra, quasi-classical or exclusively quantum behaviours, Kelvin wave cascade are, for instance, all well-known quantum turbulent features arising from vortex dynamics. In the present work we instead shift the focus on the role played by vortex dynamics in perturbing the flow of the viscous component, employing a self-consistent numerical model capable of describing the mutual interaction between superfluid vortices and normal component. 

In particular, we study the characteristics of the vorticity structures generated in the normal fluid by moving superfluid vortices (e.g. vortex dipoles and wakes) and we investigate the features of the abrupt injection of energy and enstrophy in the normal fluid triggered by superfluid vortex reconnections. We discuss the potential impact of these normal fluid disturbances in determining the normal fluid flow regime and its statistical features, and on the motion of solid particles currently employed in flow visualisation experiments.

15:00 to 15:30 Marc-Etienne Brachet [ONLINE] (ENS Paris, France) Crossover in the 1D Burgers equation from KPZ to inviscid scaling: is there a 2D analogue in the Gross-Pitaevskii equation?

First, I will give a short review of the numerical [Phil. Trans. R. Soc. A 380: 20210090, (2022)] and functional renormalization group results [PHYSICAL REVIEW LETTERS 131, 247101 (2023)] on the unpredicted crossover from Kardar-Parisi-Zhang to inviscid scaling in the 1D Galerkin-truncated Burgers equation. Then I will discuss the possibility of observing a similar crossover in 2D, in particular in the Gross-Pitaevskii equation.

15:30 to 16:00 Emil Varga (Charles University, Czech Republic) Multistability, bifurcations and critical behaviour in quasi-2D turbulence

I will present an experimental study on periodically-driven turbulence in superfluid 4He within nanofluidic systems featuring an aspect ratio of approximately 2000. Measuring the average areal density of quantized vortices for a given flow velocity amplitude, we identify multi-stable behaviour within the transition range of velocity amplitudes featuring multiple saddle-node bifurcations. The observed multistability can be modeled by a dynamical system aligning intuitively with the formation of the inverse cascade. The flow exhibits random transitions among multiple metastable branches, resulting in unpredictability, even in large-scale time-averaged quantities.
Furthermore, during an isolated transition between two metastable branches, we observe divergent power-law scaling of state lifetimes with velocity amplitude. This scaling is reminiscent of the power-law divergence of correlation time observed in critical behaviour near phase transitions. The critical exponent closely corresponds to the longitudinal correlation time critical exponent of the 2+1D directed percolation, and the observed transitions align with the behaviour seen in the switching of large-scale topology in numerical simulations of 2D flows. However, the exact mechanism behind the observed phenomena remains, at present, unknown.

Tuesday, 27 February 2024
Time Speaker Title Resources
09:20 to 10:00 Iacopo Carusotto (CNR-INO, BEC Center, Trento) Superfluids of atoms and of light as analog models of gravity: a fruitful bidirectional synergy of gravity and quantum fluid hydrodynamics

In this talk, I will present the state of the art and the new perspectives in the theoretical and experimental study of analog models of quantum field theories in flat, curved, or time-dependent backgrounds using condensed matter and optical systems.
I will start by presenting recent results on superradiant effects in different geometries. In rotating configurations, the concept of ergoregion instability provides an intuitive understanding of the well-known hydrodynamic instabilities of multiply charged vortices. Introduction of synthetic gauge fields in planar geometries extends the range of space-time metrics that can be generated and allows for analytical insight into superradiant phenomena using quantum optics concepts. In particular, the subtle relations between superradiant scattering, quantum superradiant emission and superradiant instabilities will be clarified.
I will then outline on-going work on the intriguing interplay between the Hawking emission and the quasi-normal modes of the black holes, which gives rise to a significant excitation of these latter. Speculative considerations on the possible consequences of these results in astrophysical context will be discussed.

10:00 to 10:40 Alberto Bramati (Sorbonne Université, France) Quantum fluids of Light: from quantum turbulence and driven dissipative phase transitions to analogue black holes

Photons confined in optical cavities acquire an effective mass and behave like matter particles. Moreover, an effective photon-photon interaction can be engineered when the photons propagate in a nonlinear medium, resulting in collective fluid-like behaviors of light, such as superfluidity [1].
First, I will show how, in a resonantly driven 2D polariton superfluid, the combination of the bistability behaviour of the system with flexible all-optical methods allows to control the formation and the propagation of a new class of dark solitons [2]. Due to the onset of the snake instabilities these topological defects evolve in stationary symmetric or anti-symmetric arrays of vortex streets, straightforwardly observable in CW experiments [3]. 
Then I will present a novel coherent probe spectroscopy technique allowing to observe spontaneous symmetry breaking in a parametrically driven microcavity, revealing the appearance of a diffusive Goldstone mode; a phenomenology stemming from the out of equilibrium nature of the system [4].
Finally, I will show how the properties of polariton quantum fluids can be used to simulate astrophysical objects like Black Holes and I will discuss our progresses on the experimental investigation of the Hawking effect in a quantum fluid of polaritons.
In the last part of the talk, I will introduce a new kind of quantum fluid of light, obtained on a nonlinear hot Rb vapor, in a paraxial geometry and briefly discuss our recent results on 2D-turbulent dynamics in such a system [5]. 

[1] I. Carusotto and C. Ciuti, Quantum Fluids of Light, Rev. Mod. Phys. 85, 299 (2013)
[2] A. Maître, G. Lerario, A. Medeiros, F. Claude, Q. Glorieux, E. Giacobino, S. Pigeon, and A. Bramati, Phys. Rev. X 10, 041028 (2020)
[3] F. Claude, S. V. Koniakhin, A. Maître, S. Pigeon, G. Lerario, D. D. Stupin, Q. Glorieux, E. Giacobino, D. Solnyshkov, G. Malpuech, and A. Bramati, Optica, 7, 1660 (2020)
[4] F. Claude, M. Jacquet, R. Usciati, I. Carusotto, E. Giacobino, A. Bramati, Q. Glorieux, Phys. Rev. Lett. 129, 103601 (2022)
[5] M. Baker-Rasooli, W. Liu, T. Aladjidi, A. Bramati and Q. Glorieux, Phys. Rev. A 108, 063512 (2023)

10:40 to 11:10 Clement Hainaut (Univeristy of Lille, France) Single-shot imaging of microscopic turbulent phenomena in 2D quantum fluid-of-light

Out-of-equilibrium quantum gases, especially in two dimension gives rise to complex questions due to the particular density of states and specific connectivity providing thermal and/or quantum fluctuations more importance than in 3-dimensional systems. A prominent example is the low-dimensional quantum turbulent behavior of quantum gases possessing complex microscopic dynamics through proliferation of interacting quantized vortices leading to various possibilities of energy redistribution at macroscales.

In this presentation, I will present an experimental exploration of an out-of-equilibrium quantum fluid-of-light, composed of hybrid exciton-polariton quasiparticles hosted in a semiconductor microcavity. I will provide an overview of the ultrafast nonlinear imaging technique that we have developed to measure single-shot amplitude and phase distributions of the quantum fluid. This innovative approach gives us the tools to explore the existence of quantum vortices, which serve as a distinctive signature of turbulent phenomena within the system. Lastly, I will emphasize the limitations inherent in this cutting-edge detection technique.

11:40 to 12:20 Guido Boffetta (University of Torino, Italia) Two-dimensional turbulence
12:20 to 12:50 Miguel Onorato [ONLINE] (University of Torino, Italy) An introduction to wave turbulence and anomalous correlators
14:30 to 15:00 Ashton Bradley [ONLINE] (University of Otago, New Zealand) Energy damping and diffusion of quantum vortices in Bose-Einstein condensates
15:00 to 15:30 Hayder Salman (University of Norwich, UK) Relaxation to Equilibrium of a Two-dimensional Quantum Vortex Gas

We study the relaxation of a two-dimensional (2D) ultracold Bose gas from a nonequilibrium initial state containing vortex excitations in experimentally realisable traps. Numerical simulations of a neutral point vortex model and a Bose gas governed by the 2D Gross-Pitaevskii equation in a square trap reveal that a large-scale flow field with net angular momentum emerges. A theory describing this behaviour is presented in the form of a Poisson-Boltzmann equation. The theory is subsequently verified against recent experimental work focusing on the turbulent relaxation dynamics of a two-dimensional chiral vortex gas. Using carefully designed experimental forcing protocols to inject vortices into the system, equilibria spanning the full phase diagram of the vortex gas, including vortex states near zero temperature, infinite temperature, and negative absolute temperatures are realised. The resulting experimentally measured long-time vortex distributions are found to be in excellent agreement with the mean-field predictions of the Poisson Boltzmann equation. This allows us to demonstrate that, during the relaxation dynamics, the system evolves to a state that maximises the entropy of the vortex excitations.

15:30 to 16:00 Maciej Galka (University of Heidelberg, DE) Two-dimensional Bose Gas Far From Equilibrium: Wave Turbulence and Universal Coarsening Dynamics

Understanding many-body systems far-from equilibrium is an outstanding challenge in physics. It was proposed that such systems generically feature dynamic scaling while approaching non-thermal fixed points and the associated scaling exponents would provide a classification of the nonequilibrium phenomena analogously to the equilibrium universality classes. 

I will present our experimental results with homogeneous two-dimensional Bose gas on two prototypical far-from-equilibrium problems: driven turbulence (1) and isolated-system coarsening (2). For the turbulence, we have observed two key phenomena associated with its development – the emergence of statistical isotropy under anisotropic forcing, and the spatiotemporal scaling of the momentum spectrum.

For the coarsening we have observed universal dynamic scaling with exponents that match analytical nonequilibrium field theory predictions. For different initial states we reveal universal dynamics by accounting for state-dependent prescaling effects. The methods we introduce should be applicable to any quantitative study of universality far from equilibrium.

1.    M. Galka, P. Christodoulou, M. Gazo, A. Karailiev, N. Dogra, J. Schmitt, and Z. Hadzibabic, Emergence of Isotropy and Dynamic Scaling in 2D Wave Turbulence in a Homogeneous Bose Gas, Phys. Rev. Lett. 129, 190402 (2022)
2.    M. Gazo, A. Karailiev, T. Satoor, C. Eigen, M. Galka, and Z. Hadzibabic, Universal Coarsening in a Homogeneous Two-Dimensional Bose Gas, arXiv:2312.09248 (2023)

Wednesday, 28 February 2024
Time Speaker Title Resources
09:20 to 10:00 Andreas Hemmerich (University of Hamburg, DE) Observation of continuous and discrete time crystals

I will present experimental realizations of continuous and discrete time crystals in Bose-Einstein condensates of rubidium atoms strongly coupled to a high finesse optical cavity. I will discuss how these two dynamical many-body  phases are connected via a subharmonic injection locking process.

10:00 to 10:40 Ricardo Carrettero (San Diego State University, USA) Dynamical reductions in quantum superfluids: from solitonic filaments to vortices to vortex rings

Motivated by experiments studying 2D vortex dynamics in BECs, we illustrate that, by considering these vortices as quasi-particles, one can describe their dynamics using reduced ODE models. It is then possible to study in detail the dynamics, stability, and bifurcations of vortex configurations and match the ensuing results to experimental observations. We will also explore extensions of the quasi-particle approach for 3D vortex rings which are formed when a vortex line is looped back onto itself creating a close ring that carries vorticity. We focus, in particular, on vortex rings interactions, collisions, and scattering scenarios.These reduced ODE models might serve as a platform to study some basic properties (inc. turbulence) when considering large collections of these quasi-particles.

10:40 to 11:10 Tapio Simula [ONLINE] (Swinburne University of Technology, Australia) What can artificial intelligence teach us about quantum turbulence?

We consider computer-generated configurations of quantized vortices in planar superfluid Bose-Einstein condensates. We discuss how unsupervised machine learning technology can successfully be used for classifying such vortex configurations to identify prominent vortex phases of matter. The machine learning approach could thus be applied for automatically classifying large data sets of vortex configurations obtainable by experiments on two-dimensional quantum turbulence.

11:40 to 12:20 Martin Weitz (University of Bonn, Germany) Dissipative Phases of a Bose-Einstein Condensate of Photons

Bose-Einstein condensation has been observed with cold atomic gases, exciton-polaritons, and more recently also with low-dimensional photon gases e.g. in a dye solution-filled optical microcavity. I here report on experiments observing a non-Hermitian phase transition in a photon Bose-Einstein condensate realized in the dye-microcavity platform. The dissipative phase transition occurs due to an exceptional point in the condensate that is associated with the (small) system losses. While usually Bose-Einstein condensation is separated by a smooth crossover to lasing, the presence of the here observed phase transition reveals a state of the light field characterized by a bi-exponential second order coherence that is separated by a phase transition from lasing [1]. In more recent work, we have performed a critical test of the thermal nature of the photon condensate coupled to the reservoir of photo-excitable dye molecules by probing the fluctuation-dissipation theorem in this system [2].

[1] F. Öztürk, T. Lappe, G. Hellmann, J. Schmitt, J. Klaers, F. Vewinger, J. Kroha, and M. Weitz, Science 372, 6537 (2021). 
[2] F. Öztürk, F. Vewinger, M. Weitz, and J. Schmitt, Phys. Rev. Lett. 130, 033602 (2023).

12:20 to 12:50 Marzena Szymanska (University College of London, UK) Multicomponent and spinor driven-dissipative quantum fluids: unconventional BKT, full and fractional vortices
Thursday, 29 February 2024
Time Speaker Title Resources
09:20 to 10:00 Michiel Wouters (University of Antwerp, Belgium) Vortices in polariton and photon condensates

In this talk, I will discuss the properties of quantized vortices in nonequilibrium polariton and photon condensates and how they differ from their equilibrium quantum fluid counterparts.

10:00 to 10:40 Dario Ballarini (CNR NANOTEC – Lecce, Italia) Turbulent dynamics of 2D exciton-polariton quantum fluids

Exciton-polaritons, resulting from the strong coupling of photons and excitons in semiconductor microcavities, have demonstrated their potential for exploring quantum fluids in optical systems over the past two decades. This study presents the initial evidence of turbulent dynamics and vortex clustering within 2D exciton-polariton fluids, focusing on the statistical properties of velocity and vorticity fields. By directly measuring the phase of the polariton fluid, we can identify and categorize vortices, revealing the emergence of an inverse energy cascade. Simultaneously, this measurement facilitates the extraction of complete statistics regarding the velocity field, establishing connections with classical turbulence and the universal behavior of critical systems.

10:40 to 11:10 Nina Voronova (National Research Nuclear University, Russia) Exciton-polariton ring-shaped Josephson junction

We present the first to our knowledge bosonic current-biased ring Josephson junction realised in a system of exciton-polaritons. We show that the weak link created by means of incoherent optical beam in such a ring may work in two distinct regimes in which the phase of the order parameter either smoothly reconnects between the two sides of the barrier, creating zero or non-zero winding around the ring, or experiences stochastic jumps resulting in statistics of different windings created within a given experimental setting. Drawing comparisons with superconducting rings interrupted by one Josephson junction, we provide a simple toy-model theory in terms of the 'washboard' energy landscape that explains the appearance of these two regimes. Studying the under-barrier supercurrent depending on the applied flow, we reveal a sinusoidal relation characteristic for Josephson physics. Analogies with a current-biased quantum interference devices (SQUIDs), such as the appearance of Shapiro-like steps, are discussed.

11:40 to 12:20 Mathieu Gibert (Institut Neel CNRS, France) Direct visualization of the quantum vortex lattice structure, oscillations, and destabilization in rotating 4He

Quantum vortices are a core element of superfluid dynamics and elusively hold the keys to our understanding of energy dissipation in these systems. We show that we can visualize these vortices in the canonical and higher-symmetry case of a stationary rotating superfluid bucket. Using direct visualization, we quantitatively verify Feynman’s rule linking the resulting quantum vortex density to the imposed rotational speed. We make the most of this stable configuration by applying an alternative heat flux aligned with the axis of rotation. Moderate amplitudes led to the observation of collective wave mode propagating along the vortices, and high amplitudes led to quantum vortex interactions. When increasing the heat flux, this ensemble of regimes defines a path toward quantum turbulence in rotating 4He and sets a baseline to consolidate the descriptions of all quantum fluids. REF:

12:20 to 12:50 Vishwanath Shukla (IIT Kharagpur, India) TBA
14:30 to 15:00 Rama Govindarajan (ICTS, India) The strange behaviour of inertial particles near co-rotating vortices

This talk will be in the classical limit. Inertial particles are thought to evacuate the neighborhood of vortices and collect in strain regions. We will discuss how, in rotating flow, the simplest of which is just a co-rotating vortex pair, particles can remain for long periods in the neighborhood, display extreme clustering and bifurcations from fixed points to limit cycles to chaos.

15:00 to 15:30 Luiza Angheluta [ONLINE] (University of Oslo, Norway) Vortex nucleation and dynamics in stirred Bose-Einstein condensates

Quantum vortices, carriers of quantised vorticity, induce superfluid turbulence through collective dynamics. Turbulent fluctuations can also generate phonons, which mediate dipole nucleation and annihilation events. 
To better understand phonon-vortex interactions, we analyse patterns preceding vortex nucleation from a moving obstacle. The curl of the superfluid current represents a defect density which describes both high-energy phonons and vortices. Vortex nucleation involves localising this defect density around phase slips, and this localisation process determines the rate of vortex shedding or spawning. Dynamics of interacting vortices lead to clustering of co-rotating vortices. We discuss the scaling relation between the energy spectrum of vortex clusters and their spatial correlation and show that it obeys the Kraichnan-Kolmogorov scaling of 2D classical turbulence.

15:30 to 16:00 Takeshi Matsumoto (Kyoto University, Japan) Classical turbulence in two-dimensional lid-driven cavity

We numerically study a turbulent flow of a classical incompressible fluid in a two-dimensional, so-called, lid-driven cavity. The cavity here is square and the top side (lid)  moves with a prescribed horizontal velocity. Other three sides stay still (zero velocity). The boundary condition is no-slip. It is known that, at a moderate Reynolds number such as $Re=1000$, the lid-driven cavity flow is stationary.  It is a nontrivial nonlinear stationary solution of the incompressible Navier--Stokes equations. These stationary solutions have been used as benchmarks for various numerical methods. 
In this study, we increase the Reynolds numbers more than $10^5$ using a standard Chebyshev-tau method with a suitable regularization of the lid corners. Accordingly, the flow becomes turbulent. Our objective here is to characterize this turbulence. To our knowledge, such a study of 2D lid-driven cavity turbulence is not common. Our numerical findings suggest that the mean enstrophy dissipation rate increases as $Re^{1/2}$. Also we study the mean velocity profile near the center of the bottom wall to see if it is similar to the logarithmic law of the wall. We then discuss how we can understand some of the findings.

17:30 to 18:00 Nir Navon [ONLINE] (Yale University, New Haven, CT) Many-body physics with ultracold fermions in an optical box

For the past two decades harmonically trapped ultracold atomic gases have been used with great success to study fundamental many-body physics in flexible experimental settings. However, the resulting gas density inhomogeneity in those traps makes it challenging to study paradigmatic uniform-system physics (such as critical behavior near phase transitions) or complex quantum dynamics.
The realization of homogeneous quantum gases trapped in optical boxes has marked a milestone in the quantum simulation program with ultracold atoms [1]. These textbook systems have proved to be a powerful playground by simplifying the interpretation of experimental measurements, by making more direct connections to theories of the many-body problem that generally rely on the translational symmetry of the system, and by altogether enabling previously inaccessible experiments. 

I will present a set of studies with ultracold fermions trapped in a box of light. This platform is particularly suitable to study problems of Fermi-system stability, of which I will discuss two cases: the spin-1/2 Fermi gas with repulsive contact interactions [2], and the three-component Fermi gas with spin-population imbalance [3]. I will also show our recent observation of the quantum Joule-Thomson effect for fermions [4] and the realization of strongly driven Fermi polarons [5]. These studies led to surprising results, highlighting how spatial homogeneity not only simplifies the connection between experiments and theory, but can also unveil unexpected outcomes. 

[1] N. Navon, R.P. Smith, Z. Hadzibabic, Nature Phys. 17, 1334 (2021)
[2] Y. Ji et al., Phys. Lev. Lett 129, 203402 (2022)
[3] G.L. Schumacher et al., arXiv:2301.02237
[4] Y. Ji et al., arXiv:2305.16320
[5] F.J. Vivanco et al., arXiv:2308.05746

Friday, 01 March 2024
Time Speaker Title Resources
09:20 to 10:00 Alberto Villois (University of Torino, Italy) Solitary wave solutions in dipolar quantum fluids

Dipolar Bose-Einstein condensates (dBECs) are intriguing quantum fluids with long-range interactions arising from dipole-dipole forces between their bosonic constituents. When one spatial dimension is strongly confined, these condensates exhibit a two-dimensional dispersion relation that, much like superfluid liquid helium, features a roton minimum. Here, we present a comprehensive investigation of stationary solutions in dBECs, taking into account various orientations of the magnetic moments within the dipolar gas. Effects of rotonic excitations and the system's anisotropy are accounted for in the study of the existence and stability of vortex dipole solutions and their transition into Roberts-Jones soliton solutions.

10:00 to 10:40 Nick Proukakis (University of Newcastle, UK) Turbulent Vortices in Quantum Gases and Cosmological Galactic Halos

Dynamical quenches across phase transitions and subsequent relaxation into a steady-state represent an exciting field of non-equilibrium many-body quantum physics: during such evolution, turbulent-like dynamics are induced featuring the relevant quantum vortical (or more broadly nonlinear macroscopic) excitations, whose evolution obeys scaling laws in the appropriate regimes. In this talk I will discuss examples of the emergence of such scaling laws in 2D and 3D systems, both for open and closed quantum systems [1].

Recently, the potential role of a cosmological-size Bose-Einstein condensate as an alternative `fuzzy’ model for dark matter has been gaining traction: within such framework – which will be briefly motivated on observational grounds – we showcase the qualitative analogy of a single galaxy to trapped laboratory-based quantum gases, revealing a fully-coherent galactic core surrounded by a turbulent vortex tangle [2].

[1] N.P. Proukakis, Universality of Bose-Einstein Condensation and Quenched Formation Dynamics, arXiv:2304.09541 (Encyclopedia of Condensed Matter Physics (2nd Edition), Elsevier, 2023).
[2] I.K. Liu, N.P. Proukakis and G. Rigopoulos, Coherent and incoherent structures in fuzzy dark matter halos, arXiv:2211.02565 (Monthly Notices of the Royal Astronomical Society, 521, 3625 (2023).

10:40 to 11:10 Mithun Thudiyangal (MAHE, India) Dynamics Beyond Kibble-Zurek Mechanism in a Bose-Einstein Condensate
11:40 to 13:00 Coordinated by Iacopo Carusotto Round table