Thin accretion disk signatures in hybrid metric-Palatini f(R)-gravity

In the present work, accretion onto a spherically symmetric black hole in the hybrid metric-Palatini f(R)-gravity is considered. The Novikov-Thorne model for a relativistic thin accretion disk is used. The energy flux, temperature distribution, emission spectrum and energy conversion efficiency of accretion disks around such black holes are numerically calculated. A comparison with the results for a Schwarzschild black hole is made and conclusions about the viability of the model are drawn. As a result, it is obtained that the accretion disks around black holes in hybrid metric-Palatini f(R)-gravity are colder and less luminous than in general relativity.Comment: 27 pages, 26 figure

Test of hybrid metric-Palatini f(R)-gravity in binary pulsars

We developed the parameterized post-Keplerian formalism for hybrid metric-Palatini $f(R)$-gravity. We obtained analytical expressions in the generel eccentric case for four PPK parameters: $\dot\omega$, $\dot P_{\rm b}$, $r$ and $s$. Using observational data of PSR J0737-3039 and PSR J1903+0327 we imposed restrictions on the parameters of hybrid f(R)-gravity and showed that this theory is not ruled out by the observations in strong field regime. In addition we obtained predictions for masses of systems components and found that considered astrophysical objects will be heavier than in GR.Comment: 12 pages, 4 figure

Observational Limits on Gauss-Bonnet and Randall-Sundrum Gravities

We discuss the possibilities of experimental search for new physics predicted by the Gauss-Bonnet and the Randall-Sundrum theories of gravity. The effective four-dimensional spherically-symmetrical solutions of these theories are analyzed. We consider these solutions in the weak-field limit and in the process of the primordial black holes evaporation. We show that the predictions of discussed models are the same as of General Relativity. So, current experiments are not applicable for such search therefore different methods of observation and higher accuracy are required.Comment: 7 pages, accepted to JET

Polarization and speed of gravitational waves in hybrid metric-Palatini f(R)-gravity

The question of the correspondence between the number of degrees of freedom and the number of polarization states in hybrid metric-Palatini f(R)-gravity is considered. It is shown that the scalar transverse breathing and longitudinal modes are a mixture of one polarization state. The speed of gravitational waves propagation in hybrid f(R)-gravity is calculated.Comment: 6 pages, submitted to JETP. arXiv admin note: text overlap with arXiv:1907.0691

Tests of f(R)-gravity in binary pulsars

We develop the parameterized post-Keplerian approach for class of analytic f(R)-gravity models. Using the double binary pulsar system PSR J0737-3039 data we obtain restrictions on the parameters of this class of f(R)-models and show that f(R)-gravity is not ruled out by the observations in strong field regime