Dust and radiation quantum perfect fluid cosmology: selection of time variable

Quadratic quantum cosmology with Schutz’ perfect fluid

We study the classical and quantum models of a Friedmann-Robertson-Walker (FRW) cosmology coupled to a perfect fluid in the context of f(R) gravity. We use the Schutz’ variational formalism for the perfect fluid and show that it leads to a time parameter for the corresponding dynamical system. This formalism gives rise to a Schrödinger-Wheeler-DeWitt (SWD) equation for the quantum cosmology of ...

Symmetrized Gravitational Formulism in Perfect-fluid Cosmology

We investigate the model of magnetized cosmology, and simplify the exact solutions on the perfect-fluid. We show that large-scale magnetic components of cosmological fields have mathematical connection to the angular-momentum. In the general case where cosmologies are generalized by magnetic components, it introduces some mathematical solutions for gravitational fields in a manner similar to Di...

Tilt Classifications in Perfect Fluid Cosmology

Variable Selection by Perfect Sampling

Variable selection is very important in many fields, and for its resolution many procedures have been proposed and investigated. Among them are Bayesian methods that use Markov chain Monte-Carlo (MCMC) sampling algorithms. A problem with MCMC sampling, however, is that it cannot guarantee that the samples are exactly from the target distributions. This drawback is overcome by related methods kn...

Multidimensional perfect fluid cosmology with stable compactified internal dimensions

Multidimensional cosmological models in the presence of a bare cosmological constant and a perfect fluid are investigated under dimensional reduction to D0 = 4 dimensional effective models. Stable compactification of the internal spaces is achieved for a special class of perfect fluids. The external space behaves in accordance with the standard Friedmann model. Necessary restrictions on the par...