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SUMMARY:Dynamics of superfluid states of matter - Dr Natasha Berloff (DAMT
 P)
DTSTART:20100308T170000Z
DTEND:20100308T180000Z
UID:TALK22825@talks.cam.ac.uk
CONTACT:Amanda Stagg
DESCRIPTION:When in 1937 liquid helium was first observed\nto flow with ne
 gligible viscosity through a narrow gap\, it was clear that\, at low tempe
 ratures\,\nhelium was different from ordinary fluids. The attempts to unde
 rstand this phenomenon (called superfluidity by Pyotr Kapitza) led to the 
 development of a two-fluid theory by Lev Landau. In this theory the fluid 
 is modelled as an interacting mixture of superfluid and normal fluid compo
 nents. In more recent times\, an aspect of superfluidity that has been emp
 hasized as most central is that the superfluid velocity is associated with
  the gradient of the phase of the macroscopic classical complex-valued mat
 ter field.\nSuch a description implies that the system possesses a Bose--E
 instein condensate (a form of matter that emerges when particles collapse 
 into the same lowest-energy state) -- with the matter field being the cond
 ensate wavefunction -- and\, therefore\, can be described by a nonlinear e
 quation for classical waves\, known as the nonlinear Schrodinger equation.
  This description has the ingredients necessary to produce many of the asp
 ects of superfluidity\, such as frictionless flow below the Landau critica
 l velocity\, two-fluid hydrodynamics\, quantized vortices\, and  metastabl
 e persistent flow in a doughnut-shaped geometry. These features of superfl
 uidity have been experimentally observed not only in liquid helium\, but a
 lso in ultracold gases and very recently in condensates of semiconductor m
 icrocavity polaritons -- entities comprising both matter and light.\nHow t
 he condensate model can be modified and applied to study the dynamics of t
 hese various superfluid systems is the subject of my talk.\n
LOCATION:MR2\, Centre for Mathematical Sciences
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