Revision 1

Accepted · first revision · record

Title: Dynamical exponent of the vortex-dominated fixed point in two dimensions
Plain: In a flat two-dimensional atomic gas stirred into a tangle of vortices (tiny whirlpools), simulations find correlations stretching much more slowly than standard coarsening theory predicts. The true slowing law, and whether it is universal, is not settled.
Precise: For the 2D Gross-Pitaevskii field after a quench to a dense vortex ensemble, classical-field simulations (Karl and Gasenzer, New J. Phys. 19, 093014, 2017) find a strongly anomalous fixed point with dynamical exponent $z \sim 5$ ($\beta = 1/z \sim 0.2$) and anomalous exponent $\eta \sim -3$, compared with $z$ of about 2 for ordinary vortex-annihilation coarsening. Determine $z$ at asymptotically long times and large sizes, and whether it depends on the initial vortex configuration (random versus clustered). Answer: z with uncertainty and its dependence on initial conditions.
Settled by: Gross-Pitaevskii simulations over several decades in time with a theory of vortex-cluster dynamics predicting z, checked in a uniform 2D gas experiment.
Kind: well-posed
Answer type: value
References: (empty)
Literature status: open
Status note: (empty)
Posed since: 2017