A stringy perspective on the coincidence problem

Cunillera, Francesc; Padilla, Antonio

Abstract

We argue that, for string compactifications broadly consistent with swampland constraints, dark energy is likely to signal the beginning of the end of our universe as we know it, perhaps even through decompactification, with possible implications for the cosmological coincidence problem. Thanks to the scarcity (absence?) of stable de Sitter vacua, dark energy in string theory is assumed to take the form of a quintessence field in slow roll. As it rolls, a tower of heavy states will generically descend, triggering an apocalyptic phase transition in the low energy cosmological dynamics after at most a few hundred Hubble times. As a result, dark energy domination cannot continue indefinitely and there is at least a percentage chance that we find ourselves in the first Hubble epoch. We use a toy model of quintessence coupled to a tower of heavy states to explicitly demonstrate the breakdown in the cosmological dynamics as the tower becomes light. This occurs through a large number of corresponding particles being produced after a certain time, overwhelming quintessence. We also discuss some implications for early universe inflation.

• Journal Article Type: Article
• Acceptance Date: Sep 16, 2021
• Online Publication Date: Oct 6, 2021
• Publication Date: Oct 1, 2021
• Deposit Date: Sep 17, 2021
• Publicly Available Date: Sep 17, 2021
• Journal: Journal of High Energy Physics
• Electronic ISSN: 1029-8479
• Peer Reviewed: Peer Reviewed
• Volume: 2021
• Issue: 10
• Article Number: 55
• DOI: https://doi.org/10.1007/JHEP10%282021%29055
• Public URL: https://nottingham-repository.worktribe.com/output/6244121
• Publisher URL: https://link.springer.com/article/10.1007/JHEP10(2021)055