Viscous coupled fluids in inflationary cosmology

Abstract

We consider the inflation produced by two coupled fluids in the flat Friedmann-Robertson-Walker universe. Different cosmological models for describing inflation by use of an inhomogeneous equation of state for the fluid are investigated. The gravitational equations for energy and matter are solved, and analytic representations for the Hubble parameter and the energy density are obtained. Corrections in the energy density for matter inducing the inflation and the coupling with energy are discussed. We analyze the description of inflation induced by non-constant equation-of-state parameters from fluid viscosity. The correspondence between the spectral index and the tensor-to-scalar ratio recently observed by the Planck satellite is considered.PACS numbers: 98.80.-k, 95.36.+x

Viscous fluid holographic bounce

“…Assuming that the bounce has a holographic origin we will represent the energy conservation laws in terms of the cutoff radius which, as mentioned above, is identified with the particle horizon. The motivation for describing the holographic bounce by a viscous fluid, is that the inclusion of viscosity allows one to achieve better agreement between theoretical models and astronomical observations [42][43][44].…”

Inflationary universe with a viscous fluid avoiding self‐reproduction

“…The notation in (4) is the same as in the recent paper [22]. The notation in (4) is the same as in the recent paper [22].…”

“…We choose the viscosity function ζ (N) to be proportional to the square of H [22], We choose the viscosity function ζ (N) to be proportional to the square of H [22],…”

“…Let us suppose that the viscosity function is proportional to H [22], Such an exponential form can describe powerlaw inflation.…”

“…Inhomogeneous fluid cosmology may also be interpreted as a kind of modified gravity [17,18]. Various examples of inhomogeneous viscous fluids were investigated in [19][20][21], and the recent papers [22,23] are devoted to inflationary cosmological models with viscous coupled fluids.…”