On gravitational waves in Born-Infeld inspired non-singular cosmologies

Abstract

We study the evolution of gravitational waves for non-singular cosmological solutions within the framework of Born-Infeld inspired gravity theories, with special emphasis on the Eddington-inspired Born-Infeld theory. We review the existence of two types of non-singular cosmologies, namely bouncing and asymptotically Minkowski solutions, from a perspective that makes their features more apparent. We study in detail the propagation of gravitational waves near these non-singular solutions and carefully discuss the origin and severity of the instabilities and strong coupling problems that appear. We also investigate the role of the adiabatic sound speed of the matter sector in the regularisation of the gravitational waves evolution. We extend our analysis to more general BornInfeld inspired theories where analogous solutions are found. As a general conclusion, we obtain that the bouncing solutions are generally more prone to instabilities, while the asymptotically Minkowski solutions can be rendered stable, making them appealing models for the early universe.

Constraints on Born-Infeld gravity from the speed of gravitational waves after GW170817 and GRB 170817A

“…The exactly same result is seen in the case of gravitational waves in a Friedmann-Robertson-Walker (FRW) background [16,52]. Using Eq.…”

Wormholes with nonexotic matter in Born-Infeld gravity

“…The theory is equivalent to Einstein's GR in vacuum but differs from it within matter. Since its introduction, various aspects of EiBI gravity have been studied by many researchers in the recent past, including black holes [47,[51][52][53][54][55][56][57][58][59][60], wormholes [61][62][63][64], compact stars [65][66][67][68][69], cosmological aspects [47,[70][71][72][73][74][75][76][77][78][79][80], astrophysical aspects [81][82][83], gravitational collapse [84,85], gravitational waves [86,87], implications in nongravitational contexts like particle physics [88] etc. See [89] for a recent review on various studies in EiBI gravity.…”

Constraints on generalized Eddington-inspired Born-Infeld branes

“…Therefore, one could define the above two kinds of line elements, i.e., Eqs. (25) and (26), where the previous one could be seen by the matter field and the latter could be seen by the gravitational waves [33,35,[46][47][48]. To clarify it, we first come to the matter field.…”

“…In this case, the equivalent principle is hard to preserve on the geometry defined by the auxiliary metric and the free-falling particles will instead feel a "force" from the effective energy-momentum tensor constructed by the auxiliary metric. For the gravitational waves, since the Einstein-Hilbert equation of the auxiliary metric could be obtained from the action (27), one may prefer to describe the propagations of them in the q geometry [35,46]. Now, for the sake of simplicity, we replace the equations of motion (14) and (15) as follows:…”