259 research outputs found
Wave asymptotics at a cosmological time-singularity: classical and quantum scalar fields
We investigate the propagation of the scalar waves in the FLRW universes
beginning with a Big Bang and ending with a Big Crunch, a Big Rip, a Big Brake
or a Sudden Singularity. We obtain the sharp description of the asymptotics for
the solutions of the linear Klein-Gordon equation, and similar results for the
semilinear equation with a subcritical exponent. We prove that the number of
cosmological particle creation is finite under general assumptions on the
initial Big Bang and the final Big Crunch or Big Brake.Comment: 40 p., 5 figure
Quantum cosmology and late-time singularities
The development of dark energy models has stimulated interest to cosmological
singularities, which differ from the traditional Big Bang and Big Crunch
singularities. We review a broad class of phenomena connected with soft
cosmological singularities in classical and quantum cosmology. We discuss the
classification of singularities from the geometrical point of view and from the
point of view of the behaviour of finite size objects, crossing such
singularities. We discuss in some detail quantum and classical cosmology of
models based on perfect fluids (anti-Chaplygin gas and anti-Chaplygin gas plus
dust), of models based on the Born-Infeld-type fields and of the model of a
scalar field with a potential inversely proportional to the field itself. We
dwell also on the phenomenon of the phantom divide line crossing in the scalar
field models with cusped potentials. Then we discuss the Friedmann equations
modified by quantum corrections to the effective action of the models under
considerations and the influence of such modification on the nature and the
existence of soft singularities. We review also quantum cosmology of models,
where the initial quantum state of the universe is presented by the density
matrix (mixed state). Finally, we discuss the exotic singularities arising in
the brane-world cosmological models.Comment: final version, published in Classical and Quantum Gravity as a
topical revie
- …