Momentogenesis by 3He vortices: an experimental analogue of primordial baryogenesis.

T.D.C. Bevan1 A.J. Manninen1,2 J.B. Cook1 J.R. Hook1 H.E. Hall1 T. Vachaspati3 and G.E. Volovik4,5

1 Schuster Laboratory, University of Manchester, Manchester, M13 9PL, UK
2 Now at Physics Dept., University of Jyväskylä, P.O.Box35, 40351 Jyväskylä, Finland
3 Physics Department, Case Western Reserve University, Cleveland, OH 44106, USA
4 Low Temperature Laboratory, Helsinki University of Technology, 02150 Espoo, Finland
5 Landau Institute for Theoretical Physics, 117334 Moscow, Russia

Abstract

The observed excess of matter over antimatter is believed to result from baryogenesis during phase transitions in the early universe [1, 2]. Out-of-equilibrium, anomalous baryon number violating processes could have occurred on phase separation boundaries (bubble walls) during a first order phase transition, or within topological defects such as cosmic strings [3]. The violation of baryon number conservation is a consequence of a chiral anomaly and can be viewed as the creation of particles by spectral flow of fermions from the Dirac sea to positive energy states. A spectral flow of fermionic quasiparticles can also occur in superfluid 3He and is described by a similar anomaly equation, which in this case results in the anomalous transfer of linear momentum from the ground state to the heat bath (momentogenesis). This spectral flow leads to an additional force on a moving vortex which has been measured in the Manchester rotating cryostat. In this letter we describe the correspondence between baryon number violating processes and excitation momentum violation in 3He, and present the experimental evidence for momentogenesis.

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