In this paper, we explore the pre-inflationary evolution of the universe driven by a logarithmic potential in the context of Loop Quantum Cosmology. Our analysis focuses on identifying the physically admissible initial conditions for the inflaton field that result in a successful phase of slow-roll inflation. We also evaluate the corresponding number of e-folds and examine their consistency with current observational bounds. When the kinetic energy of the inflaton dominates at the initial stage, the cosmic evolution prior to reheating naturally separates into three successive phases: the bouncing phase, the transition phase, and the slow-roll inflationary phase. Throughout the bouncing phase, the dynamics of the scale factor are largely insensitive to both the chosen initial conditions and the detailed structure of the inflationary potential. In this regime, the evolution admits an explicit analytical solution, providing a clear and model-independent description of the background behavior before the onset of inflation. In this model, the quantum bounce is governed entirely by kinetic energy, since potential energy dominated initial conditions cannot be realized over the full range of inflaton field.

Coupling Quintessence to Inflation in Supergravity The evolution of the quintessence field during a phase of chaotic inflation is studied. The inflaton and the quintesssence field are described in a supergravity framework where the coupling between the inflaton and quintessence is induced by non-renormalisable operators suppressed by the Planck mass. We show that the resulting quintessence potential during inflation possesses a time--dependent minimum playing the role of an attractor. The presence of this attractor forces the quintessence field to be small during inflation. These initial conditions are such that the quintessence field is on tracks now. Published as: Phys.Rev.D71:063530,2005 DOI: 10.1103/PhysRevD.71.063530 arXiv categories: astro-ph gr-qc hep-ph hep-th

Study of the preheating phase of chaotic inflation Particle production and its effects on the inflaton field are investigated during the preheating phase of chaotic inflation using a model consisting of a massive scalar inflaton field coupled to N massless quantum scalar fields. The effects of spacetime curvature and interactions between the quantum fields are ignored. A large N expansion is used to obtain a coupled set of equations including a backreaction equation for the classical inflaton field. Previous studies of preheating using these equations have been done. Here the first numerical solutions to the full set of equations are obtained for various values of the coupling constant and the initial amplitude of the inflaton field. States are chosen so that initially the backreaction effects on the inflaton field are small and the mode equations for the quantum fields take the form of Mathieu equations. Potential problems relating to the parametric amplification of certain modes of the quantum fields are identified and resolved. A detailed study of the damping of the inflaton field is undertaken.

large potential energy of the inflaton field was released at the end of the inflationary epoch, as the inflaton field decayed into other particles, known The chronology of the universe describes the history and future of the universe according to the current understanding of physical cosmology. In this model, the earliest stage that is supported by observational evidence is known as inflation, which occurred 13.8 billion years ago. During this epoch, space underwent a period of extremely rapid expansion in a tiny fraction of a second. Once inflatio At this point of the very early universe, the universe is thought to have expanded by at least a factor of 1026 in time on the order of 10−36 seconds. All of the mass-energy in all of the galaxies currently visible started in a sphere with a radius around 4×10−29 m, then grew to a sphere with a radius around 0.9m by the end of inflation. This phase of the cosmic expansion history is known as inflation or sometimes as the inflationary epoch. Inflation explains how today's universe has concentrations of matter, like galaxies and clusters of galaxies, rather than having matter spatially uniform through the universe. Tiny quantum fluctuations in the universe, amplified by inflation, are believed to be the basis of large-scale structures that formed much later. The mechanism that drove inflation remains unknown, although many models have been put forward. In several of the more prominent models, it is thought to have been triggered by the separation of the strong and electroweak interactions which ended the grand unification epoch. One of the theoretical products of this phase transition was a scalar field called the inflaton field. As this field settled into its lowest-energy state throughout the universe, it generated an enormous repulsive force that led to a rapid expansion of the universe. The rapid expansion meant that any potential particles (or other "unwanted" artifacts, such as topological defects) remaining from the time before inflation were now distributed very thinly across the universe.