The quantum swampland

TL;DR

The paper addresses the challenge of realizing metastable de Sitter vacua in string theory when quantum effects are included. It develops a quantum swampland perspective by analyzing quantum corrections to the effective potential, the role of vacuum choice in de Sitter space, and their backreaction on the cosmological constant. A key contribution is relating quantum instability to a swampland-like bound, yielding $c=\sqrt{\tfrac{2}{3}}\frac{\Lambda}{M_p}$ within a slow-roll framework and arguing that the Bunch-Davies vacuum is unphysical, implying quantum drainage of vacuum energy. The result suggests that quantum loop effects generically preclude time-independent de Sitter, motivating new theoretical tools and possible dualities to address quantum gravity constraints on cosmology.

Abstract

In this paper we propose a quantum version of the swampland conjecture. We argue that quantum instabilities of de Sitter space discovered using field theoretical methods, are directly related to the difficulties in finding stringy de Sitter vacua.