# Quantum Transitions Through Cosmological Singularities

## TL;DR

This paper investigates quantum transitions connecting different classical cosmological histories across singularities or bounces, providing a framework to compute probabilities for universe evolution through quantum effects.

## Contribution

It introduces a method to compute quantum transition probabilities between cosmological phases using saddle point approximation in minisuperspace models.

## Key findings

- Quantum transitions can connect inflationary histories across singularities.
- Probabilities for universe evolution through quantum bounces are derived.
- Transitions between contracting and expanding phases are characterized.

## Abstract

In a quantum theory of cosmology spacetime behaves classically only in limited patches of the configuration space on which the wave function of the universe is defined. Quantum transitions can connect classical evolution in different patches. Working in the saddle point approximation and in minisuperspace we compute quantum transitions connecting inflationary histories across a de Sitter like throat or a singularity. This supplies probabilities for how an inflating universe, when evolved backwards, transitions and branches into an ensemble of histories on the opposite side of a quantum bounce. Generalising our analysis to scalar potentials with negative regions we identify saddle points describing a quantum transition between a classically contracting, crunching ekpyrotic phase and an inflationary universe.