2018/07/31 by Arthur Hebecker, Thomas Mikhail, Pablo Soler · 1 citation
Physics and Astronomy · #Axion #Black Holes and Theoretical Physics #Boson #Classical mechanics #Context (archaeology) #Cosmology #Cosmology and Gravitation Theories #Dark energy #Dark matter #Goldstone boson #Gravitation #Instanton #Particle physics #Particle physics theoretical and experimental studies #Physics #Quantum #Quantum gravity #Quantum mechanics #Theoretical physics #Wormhole #astro-ph.CO #hep-th
paper · pdf · doi:10.3389/fspas.2018.00035
Review article for Frontiers. v3: Discussion of euclidean AdS wormholes and entanglement added
openalex created_date 2018/07/10 · openalex publication_date 2018/10/08 · arxiv created 2018/10/10 · arxiv updated 2018/10/11 · openalex updated_date 2026/08/05
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.