On Vanishing Two Loop Cosmological Constants in Nonsupersymmetric Strings

TL;DR

This paper clarifies and completes the two-loop calculation of the cosmological constant in certain nonsupersymmetric string models, confirming its vanishing at this order through corrected analysis.

Contribution

It provides the first complete two-loop computation of the cosmological constant in specific nonsupersymmetric string models, resolving previous incomplete calculations.

Findings

2-loop cosmological constant vanishes in the studied models

Previous 2-loop calculations were incomplete and are now corrected

Supports the idea of perturbative vanishing of the cosmological constant

Abstract

It has recently been suggested that in certain special nonsupersymmetric type II string compactifications, at least the first two perturbative contributions to the cosmological constant $\Lambda$ vanish. Support for perturbative vanishing beyond 1-loop (as well as evidence for the absence of some nonperturbative contributions) has come from duality arguments. There was also a direct 2-loop computation which was incomplete; in this note we explain the deficiency of the previous 2-loop calculation and discuss the complete 2-loop computation in two different models. The corrected analysis yields a vanishing 2-loop contribution to $\Lambda$ in these models.