Alford, Reddy, and Schwenzer have written a paper pointing out that a high amplitude density oscillation can
have unexpectedly large effects in a superfluid.
Cooper pairing between fermions in dense matter leads to the formation of a gap in the fermionic
excitation spectrum and typically exponentially suppresses transport properties. The authors show
that reactions involving conversion between different fermion species, such as Urca reactions
in nuclear matter, become strongly enhanced and approach their ungapped level when the matter
undergoes density oscillations of su.ciently large amplitude. They study both the neutrino emissivity
and the bulk viscosity due to direct Urca processes in hadronic, hyperonic and quark matter and
discuss different superfluid and superconducting pairing patterns.

This paper has been accepted for publication in Physical Review Letters. The preprint can be viewed online.

The research was supported by this Topical Collaboration, and also by the Nuclear Physics office of the U.S. department of Energy.