Horndeski gravity without screening in binary pulsars

Abstract

We test the subclasses of Horndeski gravity without Vainshtein mechanism in the strong field regime of binary pulsars. We find the rate of energy losses via the gravitational radiation predicted by such theories and compare our results with observational data from quasi-circular binaries PSR J1738+0333, PSR J0737-3039, PSR J1012+5307. In addition, we consider few specific cases: the hybrid metric-Palatini f(R)-gravity and massive Brans-Dicke theory.

Beyond Horndeski interactions induced by quantum effects

“…Therefore one should study gravitational scattering of the scalar field on matter degrees of freedom. The simplest suitable amplitude corresponds to the following diagram (11) Here we note matter degrees of freedom with a double plain line. We only consider tree-level interaction between the matter and gravity because of the two reasons.…”

“…It must be noted that both Horndeski and beyond Horndeski models are well motivated and widely studied [5,6,7,8,9,10,11]. In particular, beyond Horndeski models originated from degenerate higher-order scalar-tensor (DHOST) theories [12,13,14,15,16,17,18,19] and it was shown that only models (3) have no ghost modes in the spectrum of tensor perturbations propagating about a cosmological background [18,19].…”

Phenomenological Extension for Tidal Charge Black Hole

“…The system (11) was solved numerically and the corresponding plot for the critical impact parameter is presented in Fig. 3.…”

“…3. System (11) has no solutions for certain configurations of metric parameters. In full analogy with the standard Reissner-Nordstrom metric, the absence of solution for (11) indicates the absence of the shadow.…”

“…A particular modify gravity model can be considered as a suitable generalization of GR, if it provides a better description of gravitational phenomena at least at one spacial scale. Because of this feature one is only interested in modified gravity models that passes Solar system tests, for instance, such a model should have post-Newtonian parameters (and post-Keplerian parameters for binary pulsars) consistent with the current empirical data [1,7,11].…”