1. Modified gravity approaches to the cosmological constant problem
- Author
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Collaboration, The FADE, Bernardo, Heliudson, Bose, Benjamin, Franzmann, Guilherme, Hagstotz, Steffen, He, Yutong, Litsa, Aliki, and Niedermann, Florian
- Subjects
High Energy Physics - Theory ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,gr-qc ,hep-th ,FOS: Physical sciences ,General Physics and Astronomy ,General Relativity and Quantum Cosmology (gr-qc) ,General Relativity and Quantum Cosmology ,High Energy Physics - Theory (hep-th) ,cosmological constant problem ,astro-ph.CO ,self-tuning ,modified gravity ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
The cosmological constant and its phenomenology remain among the greatest puzzles in theoretical physics. We review how modifications of Einstein's general relativity could alleviate the different problems associated with it that result from the interplay of classical gravity and quantum field theory. We introduce a modern and concise language to describe the problems associated with its phenomenology, and inspect no-go theorems and their loopholes to motivate the approaches discussed here. Constrained gravity approaches exploit minimal departures from general relativity; massive gravity introduces mass to the graviton; Horndeski theories lead to the breaking of translational invariance of the vacuum; and models with extra dimensions change the symmetries of the vacuum. We also review screening mechanisms that have to be present in some of these theories if they aim to recover the success of general relativity on small scales as well. Finally, we summarise the statuses of these models in their attempt to solve the different cosmological constant problems while being able to account for current astrophysical and cosmological observations., 54 pages, 2 figures, 1 table. Invited review for Universe, Special Issue "Cosmological Constant" (https://www.mdpi.com/journal/universe/special_issues/cosmological_constant_problem)
- Published
- 2023