Revisiting pre-inflationary Universe of family of alpha-attractor in loop quantum cosmology

摘要

In this work, we revisit the dynamics of pre-inflationary Universe with a family of alpha-attractor potentials, in the framework of loop quantum cosmology, in which the big bang singularity is generically resolved purely with quantum geometric effects, and replaced by a quantum bounce. At the bounce, the background evolution is divided into two distinct classes, the first is dominated by the kinetic energy of the inflaton field and the second by the potential energy. In both classes, we find the physically viable initial conditions numerically that provide not only the slow-roll inflation, but also sufficiente-folds to be compatible with observations. In the entire range of kinetic energy dominated initial conditions (except some subsets of models 2 and 4), the background evolution prior to reheating is always split into three different phases: bouncing, transition and slow-roll inflation. In the bouncing phase, the numerical evolution of the scale factor is independent not only of the initial data, but also the inflationary potentials, as long as it is dominated by the kinetic energy, and can be well approximated by an analytical solution, whereas in the potential energy dominated case, such approximated results do not exist. Moreover, we study the phase space analysis for a class of alpha-attractor potentials, and discuss the phase space trajectories for physically viable initial conditions of the inflaton field.