Related papers: A Gravitational Mechanism for Cosmological Screeni…
In a previous paper [1] we considered the possibility that (within the early-radiation epoch) there has been (also) a short period of a significant presence of cosmic strings. During this radiation-plus-strings stage the Universe…
Previous numerical investigations of gravitational particle production during the coherent oscillation period of inflation displayed unexplained fluctuations in the spectral density of the produced particles. We argue that these features…
We show that a de Sitter spacetime is a solution of Einstein's field equations with the energy momentum tensor of a self-interacting, classical Maxwell-Boltzmann gas in collisional equilibrium. The self-interaction is described by a…
An explanation is proposed for the fact that pp-waves superpose linearly when they propagate parallely, while they interact nonlinearly, scatter and form singularities or Cauchy horizons if they are antiparallel. Parallel pp-waves do…
The particles of a classical relativistic gas are supposed to move under the influence of a quasilinear (in the particle four-momenta), self-interacting force inbetween elastic, binary collisions. This force which is completely fixed by the…
Gravitation, the universal attractive force, acts upon all matter (and radiation) relentlessly. Stable extended structures can exist only when gravity is held off by other forces of nature. This series of articles explores this interplay,…
It is possible that the expansion of the universe began with an inflationary phase, in which the inflaton driving the process also was a Higgs field capable of stabilizing magnetic monopoles in a grand-unified gauge theory. If so, then the…
In supersymmetric models of warm inflation, the large temperature of the radiation bath produced by the dissipative motion of the inflaton field may induce a significant thermal abundance of potentially dangerous gravitinos. While previous…
In order to draw out the essential behavior of the universe, investigations of early universe cosmology often reduce the complex system to a simple integrable system. Inflationary models are of this kind as they focus on simple scalar field…
Primordial magnetic fields of cosmologically interesting field strengths can be generated from gravitationally coupled electrodynamics during inflation. As the cosmological constraints require this to be power law inflation it is not…
The generation of a magnetic field in the Early Universe is considered, due to the gravitational production of the Z-boson field during inflation. Scaled to the epoch of galaxy formation this magnetic field suffices to trigger the galactic…
A central theme in cosmology is the perplexing fact that the Universe is undergoing an accelerating expansion. The latter, one of the most important and challenging current problems in cosmology, represents a new imbalance in the governing…
Gravitons produced from quantum vacuum fluctuations during an inflationary stage in the early Universe have zero entropy as far as they reflect the time evolution (squeezing) of a pure state, their large occupation number notwithstanding. A…
We show how a mass term for gravitational axions (''gravi-axions'') with a Chern-Simons coupling to gravity can naturally arise due to non-perturbative contributions from Euclidean wormholes, breaking the continuous shift symmetry of the…
It has recently been shown [1] that light vector particles produced from inflationary fluctuations can give rise to the dark matter in the Universe. A similar mechanism has been discussed in [2] for a non-minimally coupled scalar enjoying a…
Several major open problems in cosmology, including the nature of inflation, dark matter, and dark energy, share a common structure: they involve spacetime-filling media with unknown microphysics, and can be probed so far only through their…
We describe a simple and efficient mechanism by which very heavy particles are copiously created from a primordial inflationary epoch. It works for scalar fields which are massless or very light during inflation and acquire a large mass…
In an earlier work we showed that the gravitational interaction could be reproduced as a retarded dispersion interaction (Casimir interaction) between particles composed of hypothetical particles having harmonic oscillator interactions.…
Extending previous results [Phys. Rev.D {\bf 56}, 6351 (1997)], we estimate the back reaction of cosmological gravitons in the expansion dynamics, during the matter age. Tensor perturbations with scales larger than the Hubble radius are…
Unexpected astrophysical observations can be explained by gravitationally captured massive particles, which are produced inside the Sun or other Stars and are accumulated over cosmic times. Their radiative decay in solar outer space would…