J. Gariel et al., WAVE-FRONT SPEEDS IN POWER-LAW INFLATION DRIVEN BY BULK VISCOSITY ANDMATTER CREATION, Classical and quantum gravity, 14(5), 1997, pp. 1387-1391
the framework of a spatially fiat FLRW model, we account for dissipati
ve effects in a simple fluid, namely bulk viscosity and matter creatio
n. For an isentropic evolution, we study the wavefront speeds associat
ed with the characteristics of the fluid. With the assumption of a bar
otropic equation of state, we investigate the consequences on these sp
eeds of power-law behaviour for the scale factor. Our conclusion is th
at, in contrast to the exponential inflation, the isentropic power-law
inflation is compatible with causality, under conditions linking the
generalized 'adiabatic' index gamma to the exponent m of the power law
.