English

Does the Cosmological Constant really indicate the existence of a Dark Dimension?

High Energy Physics - Theory 2024-09-18 v3 General Relativity and Quantum Cosmology High Energy Physics - Phenomenology

Abstract

According to the "dark dimension" (DD) scenario, we might live in a universe with a single compact extra dimension, whose mesoscopic size is dictated by the measured value of the cosmological constant. This scenario is based on swampland conjectures, that lead to the relation ρswampmKK4\rho_{\rm swamp}\sim m_{_{\rm KK}}^4 between the vacuum energy ρswamp\rho_{\rm swamp} and the size of the extra dimension mKK1m_{_{\rm KK}}^{-1} (mKKm_{_{\rm KK}} is the mass scale of a Kaluza-Klein tower), and on the corresponding result ρEFT\rho_{_{\rm EFT}} from the EFT limit. We show that ρEFT\rho_{_{\rm EFT}} contains previously missed UV-sensitive terms, whose presence invalidates the widely spread belief (based on existing literature) that the calculation gives automatically the finite result ρEFTmKK4\rho_{_{\rm EFT}}\sim m_{_{\rm KK}}^4 (with no need for fine-tuning). This renders the matching between ρswamp\rho_{\rm swamp} and ρEFT\rho_{_{\rm EFT}} a non-trivial issue. We then comment on the necessity to find a mechanism that implements the suppression of the aforementioned UV-sensitive terms. This should finally allow to frame the DD scenario in a self-consistent framework, also in view of its several phenomenological applications based on EFT calculations.

Keywords

Cite

@article{arxiv.2308.16548,
  title  = {Does the Cosmological Constant really indicate the existence of a Dark Dimension?},
  author = {Carlo Branchina and Vincenzo Branchina and Filippo Contino and Arcangelo Pernace},
  journal= {arXiv preprint arXiv:2308.16548},
  year   = {2024}
}

Comments

18 pages; 1 Appendix. Accepted for publication in International Journal of Geometric Methods in Modern Physics (DOI:10.1142/S0219887824503055)