Abstract
We study models with a generalized inhomogeneous equation of state fluids, in the context of singular inflation, focusing to so-called Type IV singular evolution. In the simplest case, this cosmological fluid is described by an equation of state with constant w, and therefore a direct modification of this constant w fluid is achieved by using a generalized form of an equation of state. We investigate from which models with generalized phenomenological equation of state, a Type IV singular inflation can be generated and what the phenomenological implications of this singularity would be. We support our results with illustrative examples and we also study the impact of the Type IV singularities on the slow-roll parameters and on the observational inflationary indices, showing the consistency with Planck mission results. The unification of singular inflation with singular dark energy era for specific generalized fluids is also proposed.
Highlights
One of the most astonishing surprises that the scientific community experienced in the late 90’s was the observationally verified late-time acceleration of the Universe [1], an observation which was contrary to any up to that date perception or expectation for the Universe’s late-time evolution
The paper outline is: In section II, we present some essential information for the theoretical framework we shall use and we study in detail the how a singular evolution can be produced by generalized EoS models and we provide some concrete examples
When t → ±∞, we find H(t) becomes a constant H(t) → h0 and when t ∼ t0, a Type IV singularity occurs, since the Hubble rate behaves as, H(t) ∼ h0 t−t0 t1 α
Summary
One of the most astonishing surprises that the scientific community experienced in the late 90’s was the observationally verified late-time acceleration of the Universe [1], an observation which was contrary to any up to that date perception or expectation for the Universe’s late-time evolution. The homogeneous modifications assume the inclusion of terms in the EoS which depend on the effective energy density, and the inhomogeneous modifications assume terms that depend explicitly on the Hubble rate or its higher derivatives, and as was demonstrated in [7], in the context of inhomogeneous phenomenological EoS theories, it is possible to describe even phantom evolution without introducing a scalar field with negative kinetic energy Apart from this appealing feature of phenomenological EoS theories, a strong motivation to use and study these comes from the fact that inhomogeneous terms may be understood as the time-dependent bulk or shear viscosity [8] and symmetry considerations indicate such modifications of EoS [9].
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