We study the two field model for reheating based on the scalar inflaton field, φ, and its interaction with another scalar field, χ, through a Lagrangian term 1 2 gχφ,much investigated for parametric resonance or preheating. Attention is particularly on the quantum excitations of the inflaton field and the metric with a smooth transition from quantum to classical stochastic states, and with rehe...

A new version of the inflationary universe scenario is suggested which provides a possible solution of the cosmological singularity

We stochastically formulate the theory of scalar quantum electrodynamics on a de Sitter background. This reproduces the leading infrared logarithms at each loop order. It also allows one to sum the series of leading infrared logarithms to obtain explicit, nonperturbative results about the late time behavior of the system. One consequence is confirmation of the conjecture by Davis, Dimopoulos, P...

According to the inflationary universe scenario the universe in the very early stages of its evolution was exponentially expanding in the unstable vacuum-like state. At the end of the exponential expansion (inflation) the energy of the unstable vacuum (of a classical scalar field) transforms into the energy of hot dense matter, and the subsequent evolution of the universe is described by the us...

The energy scale of inflation is of much interest, as it suggests the scale of grand unified physics and also governs whether cosmological events such as topological defect formation can occur after inflation. The COBE results are used to limit the energy scale of inflation at around 60 e-foldings from the end of inflation. An exact dynamical treatment based on the Hamilton-Jacobi equations is ...

Cosmic microwave anisotropy satellites promise extremely accurate measures of the amplitude of perturbations in the universe. We use a numerical code to test the accuracy of existing approximate expressions for the amplitude of perturbations produced by single-field inflation models. We find that the second-order Stewart– Lyth calculation gives extremely accurate results, typically better than ...

Brane inflation and the production of topological defects at the end of the inflationary phase are discussed. After a description of the inflationary setup we discuss the properties of the cosmic strings produced at the end of inflation. Specific examples of brane inflation are described: D − ¯ D inflation, D3/D7 inflation and modular inflation.

Using the “δN -formalism”, We obtain the expression of the non Gaussianity of multiple-field inflationary models with the nontrivial field-space metric. Further, we rewritten the result by using the slowrolling approximation. Finally, using our result, we calculate the nonlinear parameter of the racetrack inflationary model. PACS: 98.80.Cq, 98.80.Jk, 04.20.Gz

Various issues concerning the impact of inflationary models on parameter estimation from the cosmic microwave background are reviewed, with particular focus on the range of possible outcomes of inflationary models and on the amount which might be learnt about inflation from the microwave background.

We suggest that the cosmological constant has been relaxed to its present, very small value during the inflationary stage of the evolution of the Universe. This requires relatively low scale, very long duration and unconven-tional source of inflation. We present a concrete mechanism of the cosmolog-ical constant relaxation at the inflationary epoch.