Cosmological Solutions of Low-Energy Heterotic M-Theory

TL;DR

This paper derives new exact cosmological solutions in heterotic M-theory, revealing a bouncing M5 brane behavior and identifying a persistent scale-invariant isocurvature mode, advancing understanding of early universe dynamics.

Contribution

The authors introduce a new SU(3) Toda model solution and apply symmetry transformations to generate additional cosmological solutions in heterotic M-theory.

Findings

Discovery of a bouncing M5 brane motion without explicit potentials

Identification of a scale-invariant isocurvature mode in static limits

Generation of multiple new solutions via symmetry transformations

Abstract

We derive a set of exact cosmological solutions to the D=4, N=1 supergravity description of heterotic M-theory. Having identified a new and exact SU(3) Toda model solution, we then apply symmetry transformations to both this solution and to a previously known SU(2) Toda model, in order to derive two further sets of new cosmological solutions. In the symmetry-transformed SU(3) Toda case we find an unusual "bouncing" motion for the M5 brane, such that this brane can be made to reverse direction part way through its evolution. This bounce occurs purely through the interaction of non-standard kinetic terms, as there are no explicit potentials in the action. We also present a perturbation calculation which demonstrates that, in a simple static limit, heterotic M-theory possesses a scale-invariant isocurvature mode. This mode persists in certain asymptotic limits of all the solutions we have derived, including the bouncing solution.