2008/03/31 by Nathalie Deruelle, Misao Sasaki, Yuuiti Sendouda
Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Relativity and Gravitational Theory #astro-ph #gr-qc #hep-th
paper · pdf · doi:10.1103/physrevd.77.124024
published as Phys.Rev.D77:124024,2008 · 10 pages, no figure; a clarifying comment added, typos corrected, references added
arxiv created 2008/04/02 · openalex publication_date 2008/06/18 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
In gravity theories derived from a f(R) Lagrangian, matter is usually supposed to be minimally coupled to the metric, which hence defines a ``Jordan frame.'' However, since the field equations are fourth order, gravity possesses an extra degree of freedom on top of the standard graviton, as is manifest from its equivalent description in the conformally related, Einstein, frame. We introduce explicitly this extra scalar degree of freedom in the action and couple it to matter, so that the original metric no longer defines a Jordan frame. This ``detuning'' puts f(R) gravity into a wider class of scalar-tensor theories. We argue that a ``chameleonlike'' detuning tracing the background matter density may provide purely gravitational models which account for the present acceleration of the universe and evade local gravity constraints.