Related papers: Gravitational particle production in bouncing cosm…
We calculate the reheating temperature in scenarios where heavy particles are gravitationally produced during a phase transition. We explore two distinct situations: the decay of these particles both during and after the kination phase.…
An oscillating universe cycles through a series of expansions and contractions. We propose a model in which ``phantom'' energy with $p < -\rho$ grows rapidly and dominates the late-time expanding phase. The universe's energy density is so…
In quantum cosmology, it is expected that the Big Bang singularity is resolved and the universe undergoes a bounce. We find that for Gaussian initial states, matter-gravity entanglement entropy rises rapidly during the bounce, declines, and…
We propose a mechanism to have a smooth transition from a pre-Big Bang phase to a standard cosmological phase. Such transition is driven by gravitational production of heavy massive string states that backreact on the geometry to stop the…
We calculate the number density and the energy density of a massive scalar particle conformally coupled to gravity produced by gravitational particle creation in the case the kination stage follows inflation. In this model, mode functions…
Quantum fluctuation of unstable modes about gravitational instantons causes the instability of flat space at finite temperature, leading to the spontaneous process of nucleating quantum black holes. The energy-density of quantum black…
In the inflationary scenario all the matter constituting the universe was created from the process of reheating after inflation. Recent development of the theory of reheating is briefly reviewed. The list of topics includes elementary…
We study particle production in infrared-modified gravitational theories in the contemporary universe. It is shown that in astronomical systems with rising mass density, the curvature scalar may oscillate with very high frequency. These…
Combining intervals of ekpyrotic (ultra-slow) contraction with a (non-singular) classical bounce naturally leads to a novel cyclic theory of the universe in which the Hubble parameter, energy density and temperature oscillate periodically,…
The gravitational collapse and the birth of a new universe are considered in terms of quantum mechanics. Transitions from annihilation of matter to deflation in the collapse and from inflation to creation of matter in the birth of a…
Structure in the Universe grew through gravitational instability from very smooth initial conditions. Energy conservation requires that the growing negative potential energy of these structures is balanced by an increase in kinetic energy.…
The phenomenon of cosmological gravitational particle production (CGPP) is expected to occur during the period of inflation and the transition into a hot big bang cosmology. Particles may be produced even if they only couple directly to…
One of the most important issues in an inflationary theory as standard or quintessential inflation is the mechanism to reheat the universe after the end of the inflationary period in order to match with the Hot Big Bang universe. In…
Our Universe has multiple examples of unexplained gravitational losses in black holes and neutron stars. As all of the space is squeezed out, nucleons are not easily compressible further. Gravitational loss will allow galactic black holes…
We investigate a new scenario of dark matter production in a bouncing universe, in which dark matter was produced completely out of equilibrium in the contracting as well as expanding phase. We explore possibilities of using dark matter as…
The purely gravitational dark matter (PGDM) which interacts with the standard model particles only by gravitational interaction has recently been discussed. Due to its feeble interaction, PGDM may be produced mainly by the gravitational…
We provide a detailed study of reheating in the kination regime in a scenario where the particle content is produced by gravitational production of massive scalars decaying into massless scalars and fermions which eventually reheat the…
We study the thermal formation history of four simulated galaxies that were shown in Naab et al. (2007) to reproduce a number of observed properties of elliptical galaxies. The temperature of the gas in the galaxies is steadily increasing…
Quantum fluctuation of unstable modes about gravitational instantons causes the instability of flat space at finite temperature, leading to the spontaneous process of nucleating quantum black holes. The density of vacuum energy-gain in such…
Particle production processes in the expanding universe are described within a simple kinetic model. The equilibrium conditions for a Maxwell-Boltzmann gas with variable particle number are investigated. We find that radiation and…