During a very rapid superfluid transition in 3 He following a reaction with a single neutron, the creation of topological defects (vortices) has been recently demonstrated to be in accordance with the Kibble-Zurek scenario for the cosmological analog. We discuss here the extension of the Kibble-Zurek scenario to the case when alternative symmetries may be broken and different states nucleated independently. We have calculated the nucleation probability of the various states of superfluid 3 He during a superfluid transition. Our results can explain the transition from the supercooled A phase to the B phase triggered by a nuclear reaction. The new scenario is an alternative to the well-known "baked Alaska" scenario. [S0031-9007(98)06200-0] PACS numbers: 64.60.Qb, 98.80.Cq Superfluid 3 He has an order parameter which describes the simultaneous spin, orbital, and gauge symmetries which are broken at the superfluid transition. This transition can be regarded as the closest condensed matter analogy to the cosmological grand unification transition. This analogy has been utilized in the experimental test of the Kibble cosmological mechanism of cosmic strings creation. According to this mechanism [1], at the transition separate regions of the Universe are independently nucleated with a random orientation of the gauge field in each region. The size of these initial regions (domains) depends strongly on the rapidity with which the transition is traversed. According to Zurek [2] the fundamental distance between the independently created coherent domains (in the language of [2] the distance between the ensuing vortices Z) is of the order of Z j 0 ͑t Q ͞t 0 ͒ 1͞4 , where j 0 is the zero temperature coherence length, t 0 ͑j 0 ͞y F ͒ is the characteristic time constant of the superfluid, and t Q is the characteristic time for cooling through the phase transition. As the domains grow and make contact with their neighbors, the resulting gauge field cannot be uniform. The subsequent order-parameter "glass" forces a distribution of topological defects leading to a tangle of quantized vortex lines. The first quantitative tests of defect creation during a gauge symmetry transformation have been recently performed in superfluid 3 He.The superfluid 3 He (at very low temperatures in the Grenoble experiment [3] and at relatively high temperatures in the Helsinki experiment [4]) was heated locally by neutron irradiation via the nuclear reaction:3 He 1 n 3 H 2 1 p 1 1 764 keV .The energy released by the neutron reaction heats a small region of the liquid 3 He (about 30 mm) into the normal state. This region recools rapidly through the superfluid transition owing to the rapid outflow of quasiparticles into the surrounding superfluid. For the experimental conditions of both experiments it has been proposed that quasiparticles from the heated region disperse outwards, meaning that the hot bubble is cooled rapidly from its sides and that the cooling rate is so fast that the order parameter of the surrounding superfluid 3 He cannot follow t...
We have applied the so-called HPD spectroscopy, i.e. the NMR of the homogeneously precessing domain (HPD) in superfluid SHe-B, to study the magnetic relaxation processes down to 0.3T c. The power absorbed by HPD from cw NMR rf-field was divided into several contributions corresponding to different relaxation processes. From these contributions nonhydrodynamic corrections to spin diffusion and Leggett-Takagi (L-T) relaxation were extracted for a pressure of 6 bar. Below 0.45Tc a large absorption term linear with the HPD length and increasing with the falling temperature was observed. This term could be associated with an instability of coherent precession in the nonhydrodynamic regime. The process of the HPD formation in the nonwetting regime, for T < 0.37Tc, was observed and described, leading to a new possibility to determine the d-constant of the surface energy. oo22-2291/97/o9oo-o461512.5o/o ~; 1997 Plenum Publishing Corporation
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