Boundary Conditions in Quantum String Cosmology

TL;DR

This paper explores how to impose boundary conditions in quantum string cosmology without a classical time parameter, analyzing wave packets and transitions between pre- and post-big-bang phases, leading to a novel scenario.

Contribution

It provides a detailed method for imposing boundary conditions in quantum string cosmology using intrinsic variables, offering a new perspective on pre- and post-big-bang transitions.

Findings

Constructed wave packets from different string effective actions.

Clarified the meaning of transitions between pre- and post-big-bang branches.

Proposed a scenario different from previous models.

Abstract

We discuss in detail how to consistently impose boundary conditions in quantum string cosmology. Since a classical time parameter is absent in quantum gravity, such conditions must be imposed with respect to intrinsic variables. Constructing wave packets for minisuperspace models from different tree-level string effective actions, we explain in particular the meaning of a transition between ``pre-big-bang" and ``post-big-bang" branches. This leads to a scenario different from previous considerations.