The analog acoustic metric has been originally derived for adiabatic acoustic perturbations propagating in an isentropic irrotational ideal fluid. In the framework of a Lagrangian hydrodynamic description we demonstrate that under certain conditions the usual acoustic metric can be derived for nonisentropic fluids. In a special case when the pressure takes a special form and the nonadiabatic perturbations are neglected the adiabatic acoustic perturbations corresponding to massless phonons propagate in an analog metric of the usual type. * bilic@irb.hr † hnikolic@irb.hr
We study a supersymmetric model in curved background spacetime. We calculate
the effective action and the vacuum expectation value of the energy momentum
tensor using a covariant regularization procedure. A soft supersymmetry
breaking induces a nonzero contribution to the vacuum energy density and
pressure. Assuming the presence of a cosmic fluid in addition to the vacuum
fluctuations of the supersymmetric field an effective equation of state is
derived in a self-consistent approach at one loop order. The net effect of the
vacuum fluctuations of the supersymmetric fields in the leading adiabatic order
is a renormalization of the Newton and cosmological constants.Comment: 14 pages, references added, revised argument on vacuum energy
subtraction in section 1, discussion expanded, results unchange
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