Eur. Phys. J. Plus (2021) 136: 4
https://doi.org/10.1140/epjp/s13360-020-01007-1

Regular Article

Complete set of GW polarization modes in higher-derivative $f(R,\square R,T)$ theories of gravity

Department of Theoretical Physics, Faculty of Basic Sciences, University of Mazandaran, 47416-95447, Babolsar, Iran

^b t.azizi@umz.ac.ir

Received: 24 October 2020
Accepted: 8 December 2020
Published online: 1 January 2021

Abstract

In this paper, we investigate the gravitational waves in a particular class of alternative theories of gravity which is known as higher-derivative $f(R,\square R,T)$ gravity theory. In low curvature regime and by using Newman–Penrose analysis for the linear order of the field equations, we show that in addition to the usual plus and cross polarization modes which appear in general relativity, all other modes can exist too. Actually, according to our analysis, in such a theory by choosing the proper values from the parameter space of the model, a complete set of gravitational wave polarization modes can be produced in this concept.