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G. Karra

Publications and source records attributed to G. Karra.

4 recordsLinked to original sources
arXiv2000

The Onset of Phase Transitions in Condensed Matter and Relativistic QFT

Kibble and Zurek have provided a unifying causal picture for the appearance of topological defects like cosmic strings or vortices at the onset of phase transitions in relativistic QFT and condensed matter systems respectively. There is no direct experimental evidence in QFT, but in condensed matter the predictions are largely, but not wholly, supported in superfluid experiments on liquid helium. We provide an alternative picture for the initial appearance of strings/vortices that is commensurate with all the experimental evidence from condensed matter and consider some of its implications for QFT.

cond-mat↗
arXiv1998

A reexamination of quenches in Helium 4 and Helium 3

In the light of recent difficulties in observing vortices in quenches of liquid helium 4 to its superfluid state we re-examine the Zurek scenario for their production. We argue that experiments in helium 4 are unlikely to produce true vortices in the numbers originally anticipated, if at all, because of the wide Ginzberg regime and the slowness of the mechanical quenches. On the other hand, the observed production of unambiguous vortices in neutron-bombarded helium 3, with its narrow Ginzberg regime, and fast quenches, is to be expected.

cond-mat↗
arXiv1998

A Re-examination of Quenches in $^{4}$He

In the light of recent difficulties in observing vortices in quenches of liquid $^{4}$He to its superfluid state we re-examine the Zurek scenario for their production. We find that the standard prediction is suspect because of a confusion over correlation lengths.

hep-ph↗