From a hydrodynamicist's point of view the inclusion viscosity concepts in macroscopic theory cosmic fluid would appear most natural, as an ideal is after all abstraction (excluding special cases such superconductivity). Making use modern observational results for Hubble parameter plus standard Friedmann formalism, we may extrapolate description universe back time up to inflationary era, or go opposite extreme and analyze probable ultimate fate universe. In this review discuss variety topics...

The big bang singularity could be understood as a breakdown of Einstein's General Relativity at very high energies. Adopting this viewpoint, other theories, that implement Einstein Cosmology energies, might solve the problem primeval singularity. One them is Loop Quantum (LQC) with small cosmological constant models universe moving along an ellipse, which prevents singularities like or rip, in phase space $(H,\rho)$, where $H$ Hubble parameter and $\rho$ energy density universe. Using LQC...

We demonstrate how holonomy corrections in loop quantum cosmology (LQC) prevent the Big Rip singularity by introducing a quadratic modification terms of energy density ρ Friedmann equation Friedmann-Lemaître-Robertson-Walker (FLRW) space-time consistent and useful way. In addition, we investigate whether other kind singularities like Type II,III IV survive or are avoided LQC when universe is filled barotropic fluid with state P = −ρ−f(ρ), where pressure f(ρ) function ρ. It shown that Little...

Abstract The cosmic microwave background (CMB) temperature and polarization anisotropies, as observed by independent astronomical missions such WMAP, Planck, most recently the Atacama Cosmology Telescope South Pole have played a vital role in accurately constraining cosmological theories models, establishing inflation widely accepted theory for describing physics of early Universe. However, absence definitive detection B-mode emerging discrepancies among different CMB experiments present...

The theory of nongravitational interaction between a pressureless dark matter (DM) and energy (DE) is phenomenologically rich cosmological domain which has received magnificent attention in the community. In present article we have considered some interacting scenarios with novel features: functions do not depend on external parameters Universe, rather, they intrinsic nature components; assumption unidirectional flow DM DE been extended by allowing possibility bidirectional characterized...

Working in Einstein frame, we introduce, order to avoid singularities, holonomy corrections the $f(R)=R+\ensuremath{\alpha}{R}^{2}$ model. We perform a detailed analytical and numerical study when are taken into account both Jordan frames, obtaining, dynamics which differs qualitatively, at early times, from one of original More precisely, account, Universe is not singular, starting times contracting phase bouncing enter expanding where, as model, it inflates. This completely different...

In a flat Friedmann–Lemaître–Robertson–Walker (FLRW) geometry, we consider the expansion of universe powered by gravitationally induced 'adiabatic' matter creation. To demonstrate how creation works well with expanding universe, have considered general rate and analysed this in framework dynamical analysis. The analysis hints presence non-singular (without big bang singularity) two successive accelerated phases, one at very early phase (i.e. inflation), other describes current accelerating...

An improved version of the well-known Peebles-Vilenkin model unifying early inflationary era to current cosmic acceleration, is introduced in order match with theoretical values spectral quantities provided by it recent observational data about universe. Since presents a sudden phase transition, we consider simplest way reheat universe—via gravitational production heavy massive particles—which assuming that inflation starts at GUT scales ∼ 1016 GeV, allows us use Wentzel-Kramers-Brillouin...

In the framework of a flat Friedmann-Lema{\^\i}tre-Robertson-Walker (FLRW) geometry, we present nonsingular model (no big bang singularity at finite time) our universe describing its evolution starting from early inflationary era up to accelerating phase. We found that hydrodynamical fluid with nonlinear equation state could result in such non singular scenario, which after end this stage, suffers sudden phase transition and enters into stiff matter dominated era, becomes reheated due huge...

Dark matter, one of the fundamental components universe, has remained mysterious in modern cosmology and particle physics, hence, this field is utmost importance at present moment. One foundational questions direction origin dark which directly links to its creation. In article, we study gravitational production matter two distinct contexts: firstly, when reheating occurs through production, secondly, it driven by decay inflaton field. We establish a connection between temperature mass from...

We perform a detailed investigation of the CCDM (creation cold dark matter) cosmologies using powerful techniques qualitative analysis dynamical systems. Considering wide variety creation rates ranging from constant to dynamical, we examine nature critical points and their stability obtained individual scenario consisting only matter, or matter plus second fluid with equation state. According our analyses, these scenarios predict unstable dominated points, stable accelerating attractors...

Based on Newtonian mechanics, in this article, we present a heuristic derivation of the Friedmann equations, providing an intuitive foundation for these fundamental relations cosmology. Additionally, using first law thermodynamics and Euler’s equation, derive set equations that, at linear order, coincide with those obtained from conservation stress-energy tensor general relativity. This approach not only highlights consistency between relativistic frameworks certain limits, but also serves...

A Hamiltonian approach is introduced in order to address some severe problems associated with the physical description of dynamical Casimir effect at all times. For simplicity, case a neutral scalar field one-dimensional cavity partially transmitting mirrors (an essential proviso) considered, but method can be extended fields any kind and higher dimensions. The motional force calculated our contains reactive term---proportional mirrors' acceleration---which fundamental obtain...

For bouncing cosmologies, a fine set of parameters is introduced in order to describe the nearly matter dominated phase, and which play same role that usual slow-roll inflationary cosmology. It shown that, as inflation case, spectral index running parameter for scalar perturbations cosmologies can be best expressed terms these small parameters. Further, they explicitly exhibit duality exists between Universe its contracting phase quasi de Sitter regime expanding one. The results obtained...

Non-gravitational interaction between dark matter and energy has been considered in a spatially flat Friedmann-Lemaître-Robertson-Walker (FLRW) universe. The rate is assumed to be linear the densities of it also proportional Hubble FLRW This kind model leads an autonomous dynamical system, depending on coupling parameters, could solved analytically by calculating exponential matrix, defining system. We show here that such very deep connection with some well known cosmological theories. then...

The dynamics of interacting dark matter-dark energy models is characterized through an interaction rate function quantifying the flow between these sectors. In most functions, expansion Hubble considered and sometimes it argued that, as a local property, inclusion may influence overall dynamics. This starting point present article where we consider very simple cosmic scenario vacuum cold matter by various functions originated from general function: $Q= \Gamma\rho_{c}^{\alpha...

It is stated that holonomy corrections in loop quantum cosmology introduce a modification Friedmann's equation which prevent the big rip singularity. Recently \cite{h12} it has been proved this modified Friedmann obtained an inconsistent way, what means results deduced from it, particular singularity avoidance, are not justified. The problem modify gravitational part of Hamiltonian system leading, after Legendre's transformation, to non covariant Lagrangian contradiction with one main...

Different models of universes are considered in the context teleparallel theories. Assuming that universe is filled by a fluid with equation state (EoS) $P=-\rho-f(\rho)$, for different theories and EoS we study its dynamics. Two particular cases studied detail: first one consider function $f$ two zeros (two de Sitter solutions) mimics huge cosmological constant at early times pressureless late times. In second one, loop quantum cosmology small constant, ($P=0\Leftrightarrow f(\rho)=-\rho$)...

The CMB map provided by the Planck project constrains value of ratio tensor-to-scalar perturbations, namely r, to be smaller than 0.11 (95 % CL). This bound rules out simplest models inflation. However, recent data from BICEP2 is in strong tension with this constrain, as it finds a r=0.20+0.07-0.05 0r= disfavored at 7.0 σ, which allows these inflationary survive. remarkable fact that, even though experiment was conceived search for evidence inflation, its experimental matches correctly...

We consider the matter bounce scenario in F (T ) gravity and Loop Quantum Cosmology (LQC) for phenomenological potentials that at early times provide a nearly dominated Universe contracting phase, having reheating mechanism expanding or i.e., being able to release energy of scalar field creating particles thermalize order match with hot Friedmann Universe, finally late leading current cosmic acceleration.For these potentials, numerically solving dynamical perturbation equations we have seen...