Banks-Zaks Stabilisation of Non-SUSY Strings

TL;DR

This paper introduces a novel string theory mechanism for achieving scale-separated vacua by balancing one-loop and two-loop contributions, enabling stable non-supersymmetric solutions with potential phenomenological relevance.

Contribution

It proposes a new scale separation mechanism based on stringy effects involving one-loop and two-loop vacuum energy contributions, demonstrated in explicit heterotic orbifold models.

Findings

Stable non-supersymmetric vacua can be achieved through this mechanism.

The smallness of the one-loop term relative to the two-loop term enables scale separation.

The mechanism is applicable to theories with one-loop energies from only massive states.

Abstract

It appears to be difficult within string theory to obtain genuine scale separation between spacetime and the internal sector. In this paper, we propose a novel mechanism for scale-separated vacua which hinges on stringy effects that are invisible at the level of effective field theory. We show that (meta)stable vacua can form if a super no-scale one-loop potential combines with generic two-loop contributions to the vacuum energy, in a manner analogous to Banks-Zaks fixed points. Weak string coupling and scale separation arise from the accidental smallness of the one-loop term, which receives contributions only from massive states, relative to the two-loop term. We provide a proof of concept of this mechanism in explicit non-supersymmetric heterotic toroidal orbifolds by balancing the complete one-loop contribution against the estimated two-loop term and numerically minimizing the resulting effective potential in a restricted sector of moduli space. We note that this mechanism is generically possible within any fundamental theory that has a one-loop energy that gets contributions only from massive modes.