Dr Thomas Billam gives a webinar on 'Crossover in the dynamical critical exponent of a quenched two-dimensional Bose gas' (4pm UK time)
Dr Thomas Billam (Newcastle University) gives a webinar on “Crossover in the dynamical critical exponent of a quenched two-dimensional Bose gas” at 4pm UK time. The abstract is below.
The coarsening dynamics of a many-body system quenched to an ordered phase is a well-studied problem. The dynamics typically features annealing of topological defects, and the theory of phase ordering kinetics predicts the emergence of scale-invariant dynamics with the correlation length as the only relevant length scale. The dynamical critical exponents, and possible logarithmic corrections, are generally tied to the conservation laws of the system. However, in the apparently simple case of a quenched scalar 2D Bose gas there remain open questions regarding the link between the scaling and the conservation laws in the dynamics. In recent work, we have numerically explored the crossover between dissipative and conservative dynamics in this system. In the dissipative limit we find scaling consistent with the logarithmically corrected law $ [t/\log(t/t_0)]^{1/z} $, and exponent $ z=2 $, in agreement with previous studies. Decreasing the dissipation towards the conservative limit, we find strong numerical evidence for the expected growth law $ t^{1/z} $. However, we observe a smooth crossover in $ z $ that converges to an anomalous value distinctly lower than $ 2 $ at a small finite dissipation strength. We show that this lower-than-expected exponent may be attributable to a power-law vortex mobility arising from vortex–sound interactions.