Coupling matter in modified Q gravity
Abstract
We present a novel theory of gravity by considering an extension of symmetric teleparallel gravity. This is done by introducing, in the framework of the metricaffine formalism, a new class of theories where the nonmetricity Q is nonminimally coupled to the matter Lagrangian. More specifically, we consider a Lagrangian of the form L ∼f_{1}(Q )+f_{2}(Q )L_{M} , where f_{1} and f_{2} are generic functions of Q , and L_{M} is the matter Lagrangian. This nonminimal coupling entails the nonconservation of the energymomentum tensor, and consequently the appearance of an extra force. The formulation of the gravity sector in terms of the Q instead of the curvature may result in subtle improvements of the theory. In the context of nonminimal matter couplings, we are therefore motivated to explore whether the new geometrical formulation in terms of the Q , when implemented also in the matter sector, would allow more universally consistent and viable realizations of the nonminimal coupling. Furthermore, we consider several cosmological applications by presenting the evolution equations and imposing specific functional forms of the functions f_{1}(Q ) and f_{2}(Q ), such as powerlaw and exponential dependencies of the nonminimal couplings. Cosmological solutions are considered in two general classes of models, and found to feature accelerating expansion at late times.
 Publication:

Physical Review D
 Pub Date:
 October 2018
 DOI:
 10.1103/PhysRevD.98.084043
 arXiv:
 arXiv:1806.10437
 Bibcode:
 2018PhRvD..98h4043H
 Keywords:

 General Relativity and Quantum Cosmology;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 High Energy Physics  Theory
 EPrint:
 12 pages, 4 figures