How many particles do make a fluid? Qualifying collective behavior in expanding ultracold gases

Abstract

Collective phenomena in quantum many-body systems are often described in terms of hydrodynamics, an appropriate framework when the involved particle numbers are effectively macroscopic. We propose to use experiments on expanding clouds of few and many interacting cold atoms to investigate the emergence of hydrodynamics as a function of particle number. We consider gases confined in two-dimensional elliptically-deformed traps, and we employ the manifestation of elliptic flow as an indicator of collective behavior. We quantify the response of the gas to the deformation of the trapping potential, and show how such information can be used to establish how many atoms are needed for the system to develop a degree of collectivity comparable to that expected in the hydrodynamic limit. This method permits one, in particular, to exploit observations made in expanding atomic gases to shed light on the apparent hydrodynamic behaviour of mesoscopic systems of quarks and gluons formed in the scattering of light ions in high-energy collider experiments.

arXiv comment28 pages, 8 figures

References in corpus (42)

• Many-Body Physics with Ultracold Gases
• Theory of Bose-Einstein condensation in trapped gases
• Feshbach Resonances in Ultracold Gases
• Theory of ultracold Fermi gases
• Observation of a Strongly-Interacting Degenerate Fermi Gas of Atoms
• Heavy Ion Collisions: The Big Picture, and the Big Questions
• Collision geometry fluctuations and triangular flow in heavy-ion collisions
• Triangularity and Dipole Asymmetry in Heavy Ion Collisions
• Nearly Perfect Fluidity: From Cold Atomic Gases to Hot Quark Gluon Plasmas
• Evidence for collectivity in pp collisions at the LHC
• Triangular flow in hydrodynamics and transport theory
• Measurement of interaction energy near a Feshbach resonance in a 6Li Fermi gas
• Directed and elliptic flow of charged pions and protons in Pb+Pb collisions at 40 and 158A GeV
• Creating small circular, elliptical, and triangular droplets of quark-gluon plasma
• Measurement of positive and negative scattering lengths in a Fermi gas of atoms
• Heavy Ion Collisions: Achievements and Challenges
• Relativistic hydrodynamics for heavy-ion collisions
• Expansion of an interacting Fermi gas
• Elliptic flow and incomplete equilibration at RHIC
• The physics of the centrality dependence of elliptic flow
• Investigations of anisotropic flow using multi-particle azimuthal correlations in pp, p-Pb, Xe-Xe, and Pb-Pb collisions at the LHC
• Spin-resolved single-atom imaging of ${}^6$Li in free space
• Thermodynamics of hot strong-interaction matter from ultrarelativistic nuclear collisions
• Observation of deviations from ideal gas thermodynamics in a trapped Bose-Einstein condensed gas
• Measurement of multi-particle azimuthal correlations with the subevent cumulant method in $pp$ and $p$+Pb collisions with the ATLAS detector at the LHC
• Hydrodynamic Expansion of a Strongly Interacting Fermi-Fermi Mixture
• The smallest fluid on earth
• Observation of Pauli Crystals
• Shear viscosity of a universal Fermi gas near the superfluid phase transition
• Dissipation and elliptic flow at RHIC
• Fluid Dynamics and Viscosity in Strongly Correlated Fluids
• Observation of conformal symmetry breaking and scale invariance in expanding Fermi gases
• Anomalous minimum in the shear viscosity of a Fermi gas
• Anisotropic expansion of a thermal dipolar Bose gas
• Development of transverse flow at small and large opacities in conformal kinetic theory
• Hydrodynamization in systems with detailed transverse profiles
• Hydrodynamic behavior in expanding thermal clouds of Rb-87
• Second law of thermodynamics for relativistic fluids formulated with relative entropy
• Quantum Many-Body Conformal Dynamics: Symmetries, Geometry, Conformal Tower States, and Entropy Production
• Elliptic flow in ultra-relativistic collisions with polarized deuterons
• A matter of shape: seeing the deformation of atomic nuclei at high-energy colliders
• Collective flow in single-hit QCD kinetic theory