Quantum no-scale regimes in string theory

TL;DR

This paper demonstrates that in string theory no-scale models, cosmological evolutions tend to a quantum no-scale regime where classical no-scale structure is restored, with quantum effects dominating only in certain initial conditions.

Contribution

It introduces the concept of a quantum no-scale regime in string theory and analyzes its conditions and implications at 1-loop in heterotic compactifications.

Findings

Quantum no-scale regime is attractor for certain initial conditions.

Supercritical initial conditions lead to collapsing quantum universes.

Classical no-scale structure is preserved asymptotically at the quantum level.

Abstract

We show that in generic no-scale models in string theory, the flat, expanding cosmological evolutions found at the quantum level can be attracted to a "quantum no-scale regime", where the no-scale structure is restored asymptotically. In this regime, the quantum effective potential is dominated by the classical kinetic energies of the no-scale modulus and dilaton. We find that this natural preservation of the classical no-scale structure at the quantum level occurs when the initial conditions of the evolutions sit in a subcritical region of their space. On the contrary, supercritical initial conditions yield solutions that have no analogue at the classical level. The associated intrinsically quantum universes are sentenced to collapse and their histories last finite cosmic times. Our analysis is done at 1-loop, in perturbative heterotic string compactified on tori, with spontaneous supersymmetry breaking implemented by a stringy version of the Scherk-Schwarz mechanism.