Inconsistency of modified gravity in cosmology

Autor:	Cano, Pablo A.
Rok vydání:	2024
Předmět:	General Relativity and Quantum Cosmology Astrophysics - Cosmology and Nongalactic Astrophysics High Energy Physics - Theory
Druh dokumentu:	Working Paper
Popis:	We show that there is a fundamental flaw in the application of modified gravity theories in cosmology, taking $f(R)$ gravity as a paradigmatic example. This theory contains a scalar degree of freedom that couples to the matter stress-energy tensor but not to gravitational energy. However, when applied to cosmology this theory is unable to distinguish between gravitational and non-gravitational energy. Hence the cosmological version of the theory does not coincide with its own macroscopic average, and we show that this leads to order-one discrepancies. We argue that the same inconsistency is common to many other modified gravity theories with extra degrees of freedom. Our results put into question whether these theories can make sense as the cosmological average of a fundamental theory, hence challenging their physical significance. Comment: 6 pages; v2: references added, version sent to the journal
Databáze:	arXiv
Externí odkaz:	http://arxiv.org/abs/2404.01376 Zobrazit plný text záznamu View this record from Arxiv