f(R) and Brans-Dicke Theories and the Swampland

Abstract

We discuss the viability of $f(R)$ and Brans-Dicke theories of gravity in light of the recent Swampland conjectures. We show that in the case of perfect fluid domination the swampland conjecture conditions may be easily satisfied and therefore we focus on the constraints in the vacuum theory. We derive the conditions for the swampland conjectures in $f(R)$ and Brans-Dicke framework, and find that a large portion of the parameter space is not allowed. Furthermore, we analyze particular $f(R)$ models of inflation and dark energy and in their case we set the allowed range of $R$.

19 pages, 3 figures, version accepted in JCAP

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• The Grand Canonical Multiverse and the Small Cosmological Constant
• Hitchhiker's Guide to the Swampland: The Cosmologist's Handbook to the string-theoretical Swampland Programme
• Escape from the swamp with spectator
• Hořava-Lifshitz $F(\bar{R})$ theories and the Swampland