Rotational quantum friction in superfluids: Radiation from object rotatingin superfluid vacuum

The friction experienced by a body rotating in a superfluid liquid at T=0 i s discussed. The effect is analogous to the amplification of electromagneti c radiation and spontaneous emission by a body or black hole rotating in th e quantum vacuum, first discussed by Zel'dovich and Starobinsky. The fricti on is caused by the interaction of the part of the liquid which is rigidly connected with the rotating body and thus represents a comoving detector, w ith the "Minkowski'' superfluid vacuum outside the body. The emission proce ss is the quantum tunneling of quasiparticles from the detector to the ergo region, where the energy of quasiparticles is negative in the rotating fram e. This quantum rotational friction caused by the emission of quasiparticle s is estimated for phonons and rotons in superfluid He-4 and for Bogoliubov fermions in superfluid He-3. (C) 1999 American Institute of Physics. [S002 1-3640(99)00104-8].