Euclidean Wormholes, Baby Universes, and Their Impact on Particle Physics and Cosmology

Frontiers in Astronomy and Space Sciences

Hebecker, Arthur¹  Soler, Pablo¹  Mikhail, Thomas¹ 

[1] Institute for Theoretical Physics, University of Heidelberg, Germany

关键词: string theory;    Quantum Gravity;    Euclidean wormhole;    axions;    particle physics -cosmology connection;    inflation;    weak gravity conjecture;    gravitational instanton;   

DOI  :  10.3389/fspas.2018.00035

学科分类：空间科学

来源: Frontiers

【 摘 要 】

The euclidean path integral remains, in spite of its familiar problems, an important approach to quantum gravity. One of its most striking and obscure features is the appearance of gravitational instantons or wormholes. These renormalize all terms in the Lagrangian and cause a number of puzzles or even deep inconsistencies, related to the possibility of nucleation of "baby universes". In this review, we revisit the early controversies surrounding these issues as well as some of the more recent discussions of the phenomenological relevance of gravitational instantons. In particular, wormholes are expected to break the shift symmetries of axions or Goldstone bosons non-perturbatively. This can be relevant to large-field inflation and connects to arguments made on the basis of the Weak Gravity or Swampland conjectures. It can also affect Goldstone bosons which are of physical interest in the context of the strong CP problem or as dark matter.

【 授权许可】

CC BY