On Exclusion of Positive Cosmological Constant

TL;DR

This paper discusses the potential inconsistency of a positive cosmological constant due to quantum breaking, deriving bounds that influence inflationary and dark energy models, and showing existing models remain viable.

Contribution

It introduces a string theoretic version of a bound on vacuum energy variation, extending previous ideas and demonstrating the viability of current inflationary and dark energy models.

Findings

The bound constrains the variation rate of vacuum energy.

Existing inflationary models with gravitational strength interactions are safe from quantum breaking.

The window for model building remains large despite the bounds.

Abstract

Some time ago we have suggested that positive vacuum energy exhibits a finite quantum break time, which can be a signal that a positive cosmological constant is inconsistent. From the requirement that Universe never undergoes through quantum breaking, we have derived an absolute lower bound on the speed of variation of positive vacuum energy. The same suggestion about exclusion of positive cosmological constant was made recently. We show that the new bound represents a particular string theoretic version of the old bound, which is more general. In this light, we show that the existing window still provides a large room for the inflationary and dark energy model building. In particular, the inflationary models with gravitational strength interactions, are protected against fast quantum breaking.