Related papers: Particle Production in f(R) Gravity during Structu…
Cosmological gravitational particle production (GPP) is a generic mechanism by which particles are produced during the inflationary epoch. In this work we consider the GPP of massive scalars in an effort to fully understand the spectrum of…
It is argued that the Universe reheating in bouncing cosmologies could be explained via gravitational particle production, as due to a sudden phase transition in the contracting regime. To this end, it is shown that gravitational production…
Scalar-tensor theories of gravity that embrace conformal coupling to the scalar curvature are the focal point of cosmology on discussions of inflation and late-time accelerating universe. Although there exists a stringent nucleo-synthesis…
The theoretical and observational consequences of thermodynamics of open systems, which allow particle creation are investigated in modified $f(R,T)$ ($R$ is the Ricci scalar and $T$ is the trace of energy-momentum tensor) theory of gravity…
Quantum theory of a test field on a quantum cosmological spacetime may be viewed as a theory of the test field on an emergent classical background. In such a case, the resulting dressed metric for the field propagation is a function of the…
We revisit the study of the phenomenology associated to a burst of particle production of a field whose mass is controlled by the inflaton field and vanishes at one given instance during inflation. This generates a bump in the correlators…
A variety of mechanisms in the early Universe lead to the generation of gravitational waves (GWs). We introduce here a novel source of GWs generated by vacuum fluctuations after inflation. Given that gravitons are minimally coupled…
The extreme physical conditions of Gamma Ray Bursts can constitute a useful observational laboratory to test theories of gravity where very high curvature regimes are involved. Here we propose a sort of curvature engine capable, in…
Universe heating in $R^2$-modified gravity is considered. The rates of particle production by the scalaron are calculated for different decay channels. Freezing of massive stable relics with the interaction strength typical for…
We study the production of charged scalar particles with well defined angular momentum, in the presence of an external Coulomb field on de Sitter expanding universe. This process of particle production is studied as a perturbative…
Infrared gravitons are continually produced during inflation. Like all particles, their contribution to the vacuum energy comes not only from their bare kinetic energy but also from the interactions they have with other gravitons. These…
The Universe evolution during the radiation-dominated epoch in the R^2-extended gravity theory is considered. The equations of motion for R and H are solved analytically and numerically. The particle production rate by the oscillating…
We investigate scalar particle creation in a set of bouncing models where the bounce occurs due to quantum cosmological effects described by the Wheeler-DeWitt equation. The scalar field can be either conformally or minimally coupled to…
In Chapter 1 I present the current picture of the universe and briefly review the cosmological constant problem and some of the theories proposed to solve it. The following Chapters essentially contain the published papers with some…
We consider cosmological particle production in 1+1 dimensional string theory. The process is described most efficiently in terms of anomalies, but we also discuss the explicit mode expansions. In matrix cosmology the usual vacuum ambiguity…
The effect of gravitational particle production of scalar particles on the total effective cosmic energy density (in the era after photon decoupling till the present) is considered. The effect is significant for heavy particles. It is found…
Particle creation during inflation is considered. It could be important for species whose interaction is of gravitational strength or weaker. A complete but economical formalism is given for spin-zero and spin-half particles, and the…
Quantum fields in cosmological spacetimes can experience particle production due to their interaction with the expanding background. This effect is particularly relevant for models of the very early Universe, when the energy density…
A flat FLRW cosmological model with perfect fluid comprising of variable Chaplygin gas has been studied in context of f(R; T) gravity with particle creation. The considered scale factors describe the accelerated expansion of universe due to…
In the transition between inflation and reheating, the curvature scalar typically undergoes oscillations which have significant impact on the density of gravitationally produced particles. The commonly used adiabatic vacuum prescription for…