2 research outputs found
Thermodynamics of Decaying Vacuum Cosmologies
The thermodynamic behavior of vacuum decaying cosmologies is investigated
within a manifestly covariant formulation. Such a process corresponds to a
continuous irreversible energy flow from the vacuum component to the created
matter constituents. It is shown that if the specific entropy per particle
remains constant during the process, the equilibrium relations are preserved.
In particular, if the vacuum decays into photons, the energy density and
average number density of photons scale with the temperature as and . The temperature law is determined and a generalized
Planckian type form of the spectrum, which is preserved in the course of the
evolution, is also proposed. Some consequences of these results for decaying
vacuum FRW type cosmologies as well as for models with ``adiabatic'' photon
creation are discussed.Comment: 21 pages, uses LATE
Decaying Vacuum Energy and Deflationary Cosmology in Open and Closed Universes
We consider a nonsingular deflationary cosmological model with decaying
vacuum energy density in universes of arbitrary spatial curvature. Irrespective
of the value of , the models are characterized by an arbitrary time scale
which determines the initial temperature of the universe and the
largest value of the vacuum energy density, the slow decay of which generates
all the presently observed matter-energy of the universe. If is of
the order of the Planck time, the models begin with the Planck temperature and
the present day value of the cosmological constant satisfies
as theoretically suggested. It is also
shown that all models allow a density parameter and that the
age of the universe is large enough to agree with observations even with the
high value of suggested by recent measurements.Comment: 20 pages, 2 figures (available from the authors), uses LaTe