Related papers: Particle Creation in Pre-Big-Bang Cosmology: theor…
TeV string-mass-scale strings have been excluded experimentally at colliders, as their effects have not been observed at the Large Hadron Collider (CERN). On the other hand, higher-scale string theory, with mass scales typically close to…
Particle production by expanding in the future light cone scalar quantum field is studied by assuming that the initial state is associated with the quasiequilibrium statistical operator corresponding to fluid dynamics. We calculate particle…
The Cosmic Defect theory has been confronted with four observational constraints: primordial nuclear species abundances emerging from the big bang nucleosynthesis; large scale structure formation in the universe; cosmic microwave background…
We find the spectrum P(w)dw of the gravitational wave background produced in the early universe in string theory. We work in the framework of String Driven Cosmology, whose scale factors are computed with the low-energy effective string…
Cosmic strings are one-dimensional topological defects which could have been formed in the early stages of our Universe. They triggered a lot of interest, mainly for their cosmological implications: they could offer an alternative to…
Classical and quantum gravitational instabilities, can, respectively, inflate and warm up a primordial Universe satisfying a superstring-motivated principle of "Asymptotic Past Triviality". A physically viable big bang is thus generated…
Large amplitude oscillation of cosmic field that may occur right after inflation and in the decay process of weakly interacting fields gives rise to violent particle production via the parametric resonance. In the large amplitude limit the…
We describe the detailed study and results of high-resolution numerical simulations of string-induced structure formation in open universes and those with a non-zero cosmological constant. The effect from small loops generated from the…
Important open questions in cosmology require a better understanding of the Big Bang singularity. In string and matrix theories, light-like analogues of cosmological singularities (singular plane wave backgrounds) turn out to be…
Production of axionlike particles (ALPs) by primordial magnetic fields may have significant impacts on cosmology. We discuss the production of ALPs in the presence of the primordial magnetic fields. We find a region of the ALP mass and…
General ideas of gauge/gravity duality allow for the possibility of time dependent solutions that interpolate between a perturbative gauge theory phase and a weakly curved string/gravity phase. Such a scenario applied to cosmology would…
A quantum theory is developed for the scattering of a nonrelativistic particle in the field of a cosmic string regarded as a combination of a magnetic and gravitational strings. Allowance is made for the effects due to the finite transverse…
We compare the anisotropies in the cosmic microwave background radiation measured by the COBE experiment to the predictions of cosmic strings. We use an analytic model for the $\Delta T/T$ power spectrum that is based on our previous…
According to the standard models of particle physics and cosmology, there should be a background of cosmic neutrinos in the present Universe, similar to the cosmic microwave photon background. The weakness of the weak interactions renders…
Massive scalar particle production, due to the anisotropic evolution of a five-dimensional spacetime, is considered in the context of a quadratic Lagrangian theory of gravity. Those particles, corresponding to field modes with non-vanishing…
Using some simple toy models, we explore the nature of the brane-bulk interaction for cosmological models with a large extra dimension. We are in particular interested in understanding the role of the bulk gravitons, which from the point of…
Axions have for some time been considered a plausible candidate for dark matter. They can be produced through misalignment, but it has been argued that when inflation occurs before a Peccei-Quinn transition, appreciable production can…
A string cosmology scenario ("pre-big-bang") postulates that the evolution of the Universe starts from a state of very small curvature and coupling, undergoes a long phase of dilaton-driven kinetic inflation and at some later time joins…
A primordial stochastic background of very weakly coupled massless (pseudo-)scalars can seed CMB anisotropy, when large-scale fluctuations of their stress-tensor re-enter the horizon during the matter-dominated era. A general relation…
In this paper I review some recent, interlinked, work undertaken using cosmological perturbation theory -- a powerful technique for modelling inhomogeneities in the Universe. The common theme which underpins these pieces of work is the…