Kination, Meet Kasner: On The Asymptotic Cosmology of String Compactifications

TL;DR

This paper explores the late-time behavior of string cosmology models, showing how classical decompactification can lead to a Kasner solution with collapsing dimensions, and discusses quantum effects and Swampland constraints.

Contribution

It establishes a connection between 4D kination epochs and 10D Kasner solutions, extending the understanding of runaway behaviors in string cosmology.

Findings

Decompactification can be described as a Kasner solution in 10D.

Collapse of non-compact dimensions towards a Big Crunch.

Quantum effects and Swampland constraints modify classical cosmological scenarios.

Abstract

We study runaway, kination-dominated epochs in string cosmology. We show how the apparent classical decompactification runaway of the volume modulus, described by a kination epoch in the 4-dimensional EFT, can be uplifted to a classical Kasner solution in 10d in which the non-compact dimensions collapse towards a Big Crunch. This can also be generalised for arbitrary spacetime and compactification dimensions. We conclude with some comments on how this picture is modified by quantum effects, and the need for both dynamical and kinematical Swampland constraints.