Hydrodynamics at All Scales

4 Sept 2023, 09:00 → 29 Sept 2023, 18:00 Europe/Stockholm

Albano 3: 4205 - SU Conference Room (40 seats) (Albano Building 3)

Amos Yarom, Cristina Marchetti, Jay Armas, Leo Radzihovsky

Venue

Nordita, Stockholm, Sweden

 

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Scope

Hydrodynamics has a universal character spanning various energy scales: it emerges as an effective description of black holes, accretion disks at astrophysical scales, plasmas in fusion reactors, electron flows in quantum matter or of active flows in curved membranes. The purpose of this workshop is to bring together experimental and theoretical physicists working on different aspects of hydrodynamics in order to share methods for solving problems in fluid dynamics and fostering new collaborations.

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Themes and preliminary program schedule

To be announced in due time.

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Confirmed participants

Pavel Kovtun, Natascia Pinzani, Sriram Ramaswamy, Enkeleida Lushi, Marzena Szymanska, Andrew Lucas, Larry Yaffe, Akash Jain, Graham Baker, Sergej Moroz, Piotr Surowka, Axel Brandenburg, Dhrubaditya Mitra, Niko Jokela, Ármann Gylfason, Niels Obers, John Toner, Vipin Agrawal, Andrea Amoretti, George Batzios, Daniel Brattan, Daniel Brattan, Paolo Comaron, Tejas Dethe, Alan Dorsey, Sriram Ganeshan, Aleksander Glodkowski, Daniele Gregori, Umut Gursoy, Emil Have, Johannes Hofmann, Gregory Huber, Michael Landry, Ruben Lier, Enkeleida Lushi, Ananyo Maitra, Luca Martinoia, Pawel Matus, Bernhard Mehlig, Vahid Nasirimarekani, Gianbattista-Piero Nicosia, Andre Oliveira Pinheiro, Francisco Pena-Benitez, Kitinan Pongsangangan, Nick Poovuttikul, Giuseppe Pucci, Dylan Reynolds, David Rodriguez, Igor Rogachevskii, Alberto Roper Pol, Shuvayu Roy, Koenraad Schalm, Ashish Shukla, Jonas Veenstra, Sebastian Waeber.

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Accommodation

Nordita provides a limited number of rooms in the Stockholm apartment hotel, BizApartments, free of charge for accepted participants and after application evaluation. These hotel apartments are designed for long-stay accommodation with fully-equipped kitchens and standard amenities. For more details, see here. Subject to availability, it is also possible to arrange a larger apartment (for families) upon request. Please specify the type of accommodation you would like in the application form, including if you will make your own arrangements. Any special requests should be made using the comments section of the application form.

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Travel support

We can cover travel expenses partly or fully of a limited number of participants. If you would like to apply for travel funding check the box "apply for travel grant" in the registration form. We encourage participants to use their own travel grants if possible as to allow for supporting a larger number of participants.

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Application/Registration

For participation in the program, please register/apply using the link "Application" in the sidebar at the top. The deadline for applications is July 1st 2023. 

We encourage a minimum stay of one week. Due to space restrictions, the total number of participants is strictly limited.

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Organisers

Jay Armas (U. Amsterdam), Cristina Marchetti (UCSB), Leo Radzihovsky (U. Colorado), Amos Yarom (Technion).

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This workshop has the generous and kind support of Nordita, Delta Institute for Theoretical Physics (Delta ITP) in the Netherlands, and the Dutch Institute for Emergent Phenomena.

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Monday 4 September

1 Hydrodynamics: a theoretical physicist’s perspective

Speaker: Pavel Kovtun

2 Non-invertible symmetries, chiral magnetohydrodynamics and lattice QCD

Speaker: Napat Poovuttikul

Tuesday 5 September

3 Hydrodynamics of active matter: from motile organisms to non-reciprocal magnets

I will present a theoretical framework for building symmetry-based coarse-grained descriptions of systems whose constituents receive a sustained free-energy supply that they convert to work. I'll summarise progress in the field and offer a prospective outlook on its future. I hope to build bridges to other parts of the large enterprise of hydrodynamic approaches to nonequilibrium physics.

Speaker: Sriram Ramaswamy

4 Unflappable flocks at fluid interfaces

More than two decades ago it was shown [PRL 89, 058101 (2002)] that flocks in fluids are unstable at least in the viscous limit. This instability of uniaxial orientational order in bulk active fluids is an inescapable consequence of the conservation of total mass and momentum. In this talk, I will use the fluctuating, broken-symmetry hydrodynamic framework for internally driven (i.e., active) systems to show that the very activity that conspires with conservation laws to destroy bulk nematic or polar ordering can instead promote it, with radically suppressed fluctuations, in a layer of active fluid in contact with a solid or fluid medium. These escapes from the bulk instability and active stabilisation of uniaxial order via dynamical, nonequilibrium analogues of the Anderson-Higgs mechanism, would be impossible in equilibrium systems in which the existence of order and all equal-time correlators are independent of dynamics and the presence or absence of conservation laws.

Speaker: Ananyo Maitra

17:00 Reception

Wednesday 6 September

5 Geometrical and topological mysteries of intracellular membranes

Speaker: Gregory Huber

6 Elastic membrane hydrodynamics

Speaker: Varghese Mathai

Thursday 7 September

7 Beyond Drude transport in hydrodynamic metals

Hydrodynamics provides an effective macroscopic description for systems near thermal equilibrium. In hydrodynamic metals, due to the weak explicit breaking of translation invariance from impurity and/or phonon scattering, momentum relaxes slowly with a certain rate, which formally appears on the right-hand side of the momentum dynamical equation and causes a Drude-like peak in the thermoelectric conductivities. In this talk, I will discuss a systematic approach for constructing a hydrodynamic theory which incorporates momentum-relaxing gradient corrections beyond Drude i.e. arising at subleading order in the gradient expansion. The subleading terms arise at the same order as the shear and bulk viscosities. They effectively renormalize the weight of the Drude pole in the thermoelectric conductivities, and contribute to the dc conductivities at the same order as the incoherent conductivities. Our model is able to perfectly capture the transport properties of strongly-coupled holographic
metallic phases with broken translation invariance.

Speaker: Ashish Shukla

8 Surprises in Fermi liquid theory: Anomalously long lifetimes in 2D systems

I will give an introduction to transport phenomena and transport calculations in non-relativistic Fermi liquids. Such systems encompass interacting electron gases in the hydrodynamic regime, which has recently been accessed experimentally, but also atomic quantum gases. In particular, I will present calculations of the shear viscosity within kinetic theory at finite temperature. I will then discuss in more detail the structure of quasiparticle scattering in the presence of a Fermi surface in two-dimensional systems, which reveals a parity-dependence of relaxation rates. Such an odd-even effect gives rise to a new transport regime with long-lived odd-parity modes in addition to hydrodynamic ones, and the talk will conclude by discussing signatures of this regime in the collective mode spectrum.

Speaker: Johannes Hoffman

Friday 8 September

9 Hydrodynamics of pseudo-Goldstones and singular Goldstones

At all scales, phases of matter can be found which can be understood from the point of view of spontaneous symmetry breaking. For such phases of matter, it is possible to formulate an adequate hydrodynamic description by including Goldstone fields. In my seminar, I will consider ways in which damped hydrodynamics can arise when the spontaneous symmetry breaking is undermined weakly. This undermining can happen either through explicit symmetry breaking, which gives rise to pseudo-Goldstones, or through topological defects, which give rise to singular Goldstones. I will then discuss how to systematically construct the most general hydrodynamic theory of pseudo-Goldstones and singular Goldstones and what are the distinct effects on transport.

Speaker: Ruben Lier

10 Hydrodynamics of a relativistic charged fluid in the presence of a periodically modulated chemical potential

We study charged relativistic hydrodynamics driven by an external chemical potential made periodic in order to mimick the charge modulation generated by an ionic lattice. The background periodicity fluctuations are mixing Bloch waves rather than independent single momentum Fourier waves. The modes at momenta separated by integer multiples of the modulation wavevector interact and lead to novel physical effects which bear resemblance to the physics of cuprates. We connect our results to explicit realizations in AdS/CFT models with an outlook towards condensed matter applications.

Speaker: Nicolas Chagnet

Monday 11 September

11 Bernhard Mehlig - Statistical models for turbulent aerosols

When very small particles are suspended in a fluid in motion, they tend to follow the flow. How such
tracer particles are mixed, transported, and dispersed by turbulent flow has been successfully described by statistical
models. Heavy particles, with mass densities larger than that of the carrying fluid, can detach from the flow. This
results in preferential sampling, small-scale fractal clustering, and large collision velocities. To describe these effects
of particle inertia, it is necessary to consider both particle positions and velocities in phase space. In recent years,
statistical phase-space models have significantly contributed to our understanding of inertial-particle dynamics in
turbulence. These models help to identify the key mechanisms and non-dimensional parameters governing the
particle dynamics, and have made qualitative, and in some cases quantitative predictions. This article reviews
statistical phase-space models for the dynamics of small, yet heavy, spherical particles in turbulence. We evaluate
their effectiveness by comparing their predictions with results from numerical simulations and laboratory
experiments, and summarise their successes and failures.

12 Sebastian Waeber - Turbulent flow from a stochastic gravitational potential

The fluid/gravity correspondence, the duality between the dynamics of black holes in Anti-de Sitter
space and fluid behaviour of field theories, may be used to geometrize turbulent flow and translate statistical
properties of turbulent fluids into geometric observables. Likewise turbulent solutions to Navier-Stokes equations
can be obtained from black hole dynamics. We study the fluid phase of conformal matter driven by a randomly
fluctuating gravitational potential, by numerically solving the evolution of a black hole in Anti-de Sitter space with a
fluctuating, stochastic boundary metric. We discuss subtleties regarding the fluid's compressibility and the
non-relativistic limit in this set up, and identify observables in the dual gravity theory which correspond to
correlators of the fluid velocity and their higher moments with the goal to translate anomalous scaling exponents
into geometry.

Tuesday 12 September

13 Piotr Surówka - Elasticty, hydrodynamics and fractons

This seminar explores the evolving field of fractons, quasiparticles with limited mobility, and their
relationship with elasticity and fluid mechanics. We review key developments in fracton-elasticity dualities, using
examples from Cauchy, Cosserat, and curved elasticity theories to demonstrate their significance. The talk will also
introduce a hydrodynamic theory for dipole moment-conserving excitations and discuss its generalization to
dipole-conserving superfluids.

14 Akash Jain - Aspects of Schwinger-Keldysh hydrodynamics

Schwinger-Keldysh effective field theory (SK-EFTs) is a framework for systematically including stochastic
thermal fluctuations into the hydrodynamic framework. In this talk, we will review some aspects of SK hydrodynamics
and how it goes past the regime of applicability of the conventional Martin-Siggia-Rose (MSR) formulation of
stochastic hydrodynamics. We will pay particular attention to the dynamical Kubo-Martin-Schwinger (KMS)
symmetry, which is responsible for implementing n-point fluctuation-dissipation theorems (FDTs) in SK-EFTs. Time
permitting, we will also discuss the extensions of these ideas to non-conserved degrees of freedom, in particular to
the Muller-Israel-Stewart model of relativistic hydrodynamics.

17:00 Reception at Proviant Restaurant (location of the canteen where we have lunch)

Wednesday 13 September

15 Laurence Yaffe - Relativistic hydro for quark-gluon plasma: applicability, initial conditions & limits of validity.

16 Michael Landry - Macroscopic quantum effects: a systematic formulation of chiral anomalous magnetohydrodynamics

We introduce a novel approach for understanding how electromagnetic fields interact with quantum
matter, giving rise to macroscopically observable quantum mechanical effects. This method is useful for
systematically studying complex phenomena involving strong magnetic fields, with applications to a wide variety of
physics subfields including condensed matter, nuclear, and astrophysics. Specific applications include the study of
Dirac and Weyl semimetals, electroweak plasmas, heavy ion collisions, and neutron stars.
We focus specifically on magnetohydrodynamics (MHD) with an Adler-Bell-Jackiw (ABJ) anomaly (also known as the
triangle anomaly or chiral anomaly). This new framework allows us to consolidate various effects, like the chiral
magnetic effect, electric separation effect, and much more, into a single comprehensive model. As a testable
prediction, we explore a new type of chiral wave that we term the chiral magnetic electric separation wave. This
prediction is emphatically distinct from the previously-predicted chiral magnetic wave which we show fails to exist in
the presence of dynamical electromagnetic fields. Finally, we introduce a simplified model to investigate the outcome
of the well-known chiral instability and comment on a potential application to neutron stars.

15:00 Fika (coffee and pastries at the 6th floor)

Thursday 14 September

17 Alan Dorsey - Hydrodynamics of supersolids

In this talk I will provide an overview of the search for supersolids, an elusive state of matter in which
superfluid and solid behaviors coexist. Theoretical speculations on the coexistence of off-diagonal long-range order
and crystalline order (with the accompanying shear rigidity) date from the 1960s; after a long dormant period, there
was great excitement in 2004 when several experimental groups announced the observation of nonclassical
rotational inertia, a hallmark of the putative supersolid phase, in samples of solid 4He. Alas, careful experiments from
2004-2012 determined that the signals of a supersolid phase were most likely a result of defects in the solid that
affected the shear modulus, with little to do with ODRLO. However, the experiments stimulated interest in a
hydrodynamic theory of supersolids, with the identification of new collective modes. I will review this hydrodynamic
theory, in which point defects in the solid play a starring role. While not immediately relevant to solid 4He, variants of
this work may be relevant to supersolid phases observed in dipolar atomic gases over the past five years.

Friday 15 September

18 Axel Brandenburg - Hydrodynamics with magnetic fields: new qualities

The presence of magnetic fields brings entirely new qualities into the game. Magnetic fields imply the
presence of an additional energy reservoir, and energy can flow between magnetic and kinetic energies. Unlike
hydrodynamics, where energy gets thermalized through viscous heating, it can now also be thermalized through
Joule heating. The macroscopic dynamics, and the relative importance of both heating processes depend on
ill-known microphysical processes and transport coefficients. Magnetic fields also facilitate the emergence of
spatio-temporal coherence associated with inverse cascading. Spatio-temporal coherence can also emerge in
ordinary hydrodynamics, but such effects are mostly due to boundaries. When magnetic fields are strong, there can
be inverse cascading of two different types: with and without net magnetic helicity. The helical case is relevant in all
types of large-scale dynamos in much of astrophysics ranging from planetary and stellar scales all the way to
galactic scales. Even the entire Universe could have magnetic fields with magnetic helicity of one sign, for example
if it is generated by the chiral magnetic effect, or during inflation from an axion-like field. A major qualitative
difference to hydrodynamics is the conservation of magnetic helicity in conducting media. But even in the absence
of net magnetic helicity, this conservation plays an important role due to the conservation of what is now known as
the Hosking integral. This is a very new subject and we are just beginning to appreciate the full extent
of the phenomenon of inverse cascading in cases when the net magnetic helicity vanishes. In addition to numerical
simulations and astrophysical observations, there are laboratory experiments that allow us to study important
processes such as dynamos and reconnection. The Pencil Code is an example of a community effort to develop a
continuously growing toolbox to address many of those questions. Laboratory experiments, on the other hand,
focus often on liquid sodium experiments, but many of the processes can also be studied in plasma experiments.

Monday 18 September

19 Ármann Gylfason - Non-intrusive Lagrangian temperature measurements in convective turbulent flows

Turbulent convection, and thermal flows, remain interesting areas of study due to the presence of
complex structures and multiscale coupling. Advances in experimental methods have rapidly improved measurable
quantities of convective flows systems, and expanded the range of parameters that are accessible. Lagrangian
Particle Tracking is among other optical measurement techniques that have gained considerable momentum in the
last few decades with rapid development of imaging systems and computational capabilities and replaced
point-based measurement of flow quantities to some extent. In this presentation I will present our recent attempts to
expand the traditional Lagrangian Particle Tracking methodology to simultaneously detect the Lagrangian
temperature. In this work, we have found that one such promising experimental method is a temperature
measurement based on the application of thermochromic liquid crystals.

Tuesday 19 September

20 Umut Gursoy - Hydrodynamics of quarks

I will review recent developments, state of the arts and some of the open problems in relativistic
hydrodynamics applied to the deconfined matter of quarks and gluons. I will focus on how the data obtained in heavy
ion collisions is matched onto results of hydrodynamic simulations and how the various transport properties of the
quark-gluon plasma can be obtained through Bayesian analysis. Among the many open problems, I will discuss i)
inclusion of electromagnetic properties of the quark-gluon matter, and, ii) effects of vorticity e.g. explanation of the
recently observed global spin polarization of hadrons through spin transport. These problems urge us to develop a
full-fledged relativistic theory of spin-magneto-hydrodynamics. I will discuss challenges associated to this theory,
and, if time permits also how holography could help solving these challenges.

17:00 Reception catered by Proviant Restaurant (location: big kitchen area at Nordita floor 6)

Wednesday 20 September

21 Natalia Pinzani Fokeeva - Horizon symmetries, hydrodynamics, and chaos

To write fluid dynamics from a modern effective field theory point of view, an infinite reparameterization
symmetry is required. Curiously, black hole horizons possess the same redundancy. In this talk, I will show how
horizon symmetries can be interpreted as symmetries of a dual hydrodynamic theory. In addition, I will show how the
horizon structure leads to additional symmetries that are responsible for the chaotic behavior of the dual theory.

Thursday 21 September

22 Marzena Szymanska - Driven-dissipative non-equilibrium quantum fluids of light

23 Sriram Ganeshan - Dynamics of Fractional Quantum Hall Effect: Lessons from geophysics

In this talk, I will explore the similarities and differences between the fluid dynamical equations that
govern ocean waves and the "hydrodynamics" of Fractional Quantum Hall (FQH) fluids. The linearized edge dynamics
of the FQH hydro reveals two chiral edge modes propagating in the same direction: a non-dispersing Kelvin mode
(observed on coasts) and a dispersing chiral boson mode. The presence of two modes at the edge of a Laughlin state
is somewhat perplexing because only one chiral mode is expected for these states.Contrary to what is discussed in
literature, I will explain that the Kelvin mode is incompatible with the gauge anomaly and, thus, cannot be associated
with the charge transport at the edge. However, the chiral boson mode is consistent with the anomaly-induced chiral
edge dynamics. By invoking a fluid dynamical perspective, we can gain further insights into the non-linear dynamics
of FQH edge.

Friday 22 September

24 John Toner - Birth, Death, and Flocking: The Hydrodynamics of Dry Active matter

In creatures ranging from birds to fish to wildebeest, we observe the collective and coherent motion of
large numbers of organisms, known as ‘flocking’. In this talk, I'll use the hydrodynamic theory of flocking to explain
why a crowd of people can all walk, but not point, in the same direction. Along the way I'll illustrate how one goes
about formulating a hydrodynamic theory for heretofore unconsidered states and system, using powerful techniques
from theoretical condensed matter physics such as hydrodynamic theories, the gradient expansion, and the
renormalization group, and using concepts from fluid mechanics.

25 Enkeleida Lushi - Micro-swimmers in complex confinement

Interactions between micro-swimmers and solid boundaries play an important role in many biological
and technological processes. I will discuss our ongoing work in modeling and simulations that aim to understand the
motion of micro-swimmers such as bacteria, micro-algae, spermatozoa or active colloids in various confinements or
in structured environments. Our results highlight a complex interplay of the hydrodynamic and contact interactions of
the individuals with each-other and the boundaries to give rise to non-trivial individual and collective behavior.