New class of hybrid metricPalatini scalartensor theories of gravity
Abstract
A class of scalartensor theories (STT) including a nonmetricity that unifies metric, Palatini and hybrid metricPalatini gravitational actions with nonminimal interaction is proposed and investigated from the point of view of their consistency with generalized conformal transformations. It is shown that every such theory can be represented onshell by a purely metric STT possessing the same solutions for a metric and a scalar field. A set of generalized invariants is also proposed. This extends the formalism previously introduced in [1]. We then apply the formalism to Starobinsky model, write down the Friedmann equations for three possible cases: metric, Palatini and hybrid metricPalatini, and compare some inflationary observables.
 Publication:

Journal of Cosmology and Astroparticle Physics
 Pub Date:
 July 2020
 DOI:
 10.1088/14757516/2020/07/003
 arXiv:
 arXiv:2003.02741
 Bibcode:
 2020JCAP...07..003B
 Keywords:

 General Relativity and Quantum Cosmology;
 High Energy Physics  Theory
 EPrint:
 34 pages in LaTeX, comments and references added, final version published in JCAP