相关论文: Particle production in string cosmology models

Recent BICEP2 detection of low-multipole B-mode polarization anisotropy in the cosmic microwave background radiation supports the inflationary universe scenario and suggests a large inflaton field range. The latter feature can be achieved…

We discuss some peculiar properties of the stochastic graviton background predicted by string cosmology. At Planckian times, for the values of the parameters of the model which are more interesting for the detection in gravitational wave…

We compute the spectral distribution of the quantum fluctuations of the vacuum, amplified by inflation, after an arbitrary number of background transitions. Using a graphic representation of the process we find that the final spectrum can…

We analyse numerically the onset of pre-big bang inflation in an inhomogeneous, spherically symmetric Universe. Adding a small dilatonic perturbation to a trivial (Milne) background, we find that suitable regions of space undergo…

We present the first calculation of the bispectrum of the matter perturbations induced by cosmic strings. The calculation is performed in two different ways: the first uses the unequal time correlators (UETCs) of the string network -…

We study the pair creation of point-particles and strings in a time-dependent, weak gravitational field. We find that, for massive string states, there are surprising and significant differences between the string and point-particle…

Time-like linear dilaton triggers, at the classical level, the creation of closed folded strings at an instant. We show that in cosmology these instant folded strings induce negative pressure at no energy cost. Hence they seem to allow an…

We derive a generalized equation for the evolution of tensor perturbations in a cosmological background, taking into account higher-curvature contributions and a tree-level coupling to the dilaton in the string frame. The equation is…

A spectrum of relic stochastic gravitational radiation, strongly tilted towards high frequencies, and characterized by two basic parameters is shown to emerge in a class of string theory models. We estimate the required sensitivity for…

The recent measurements of cosmological parameters by the Planck collaboration favors inflationary models with a redshifted spectrum and a very low tensor-to-scalar ratio. Two well-studied scenarios in the particle physics/string theory…

Recently, it has been shown in Ref.[1] that the string thermodynamic fluctuation may lead to a scale invariant spectrum of scalar metric perturbation. However, its realization is still in study. In this note we suppose that the correlation…

String Gas Cosmology is a model of the evolution of the very early universe based on fundamental principles and key new degrees of freedom of string theory which are different from those of point particle field theories. In String Gas…

We present an overview of inflationary models derived from string theory focusing mostly on closed string moduli as inflatons. After a detailed discussion of the eta-problem and different approaches to address it, we describe possible ways…

A continuous process of creation of particles is investigated as a possible connection between the inflationary stage with late cosmic acceleration. In this model, the inflationary era occurs due to a continuous and fast process of creation…

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…

Adiabatic (curvature) perturbations are produced during a period of cosmological inflation that is driven by a single scalar field, the inflaton. On particle physics grounds -- though -- it is natural to expect that this scalar field is…

We derive a class of solutions to the string sigma-model equations for the closed bosonic string. The tachyon field is taken to form a constant condensate and the beta-function equations at one-loop level are solved for the evolution of the…

We show that inflation in type IIB string theory driven by the volume modulus can be realized in the context of the racetrack-based Kallosh-Linde model (KL) of moduli stabilization. Inflation here arises through the volume modulus…

In spite of the phenomenological successes of the inflationary universe scenario, the current realizations of inflation making use of scalar fields lead to serious conceptual problems which are reviewed in this lecture. String theory may…

String-loop effects may generate very weak matter couplings for a (massless) dilaton. We examine limits on the shift of such a dilaton toward its present equilibrium value from big-bang nucleosynthesis and the binary pulsar. On the other…