New Ekpyrotic Quantum Cosmology

TL;DR

This paper introduces a higher-derivative modification to ekpyrotic instantons, enabling a smooth, non-singular bounce in quantum cosmology, and demonstrates that the universe's wavefunction remains classical across this transition.

Contribution

It presents a novel approach to resolving singularities in ekpyrotic instantons by incorporating ghost condensates, leading to a fully non-singular, calculable cosmological history.

Findings

Achieved a non-singular bounce in ekpyrotic models

Maintained classicality of the universe's wavefunction across the bounce

Provided a basis for a complete, non-singular cosmological evolution

Abstract

Ekpyrotic instantons describe the emergence of classical contracting universes out of the no-boundary quantum state. However, up to now these instantons ended in a big crunch singularity. We remedy this by adding a higher-derivative term, allowing a ghost condensate to form. This causes a smooth, non-singular bounce from the contracting phase into an expanding, kinetic-dominated phase. Remarkably, and although there is a non-trivial evolution during the bounce, the wavefunction of the universe is "classical" in a WKB sense just as much after the bounce as before. These new non-singular instantons can thus form the basis for a fully non-singular and calculable ekpyrotic history of the universe, from creation until now.