scholarly journals Kinematic reconstructions of extended theories of gravity at small and intermediate redshifts

2020 ◽  
Vol 135 (1) ◽  
Author(s):  
Marco Calzá ◽  
Alessandro Casalino ◽  
Orlando Luongo ◽  
Lorenzo Sebastiani
Keyword(s):  
Extended Theories Of Gravity ◽  
Theories Of Gravity ◽  
Intermediate Redshifts ◽  
Extended Theories

Shadow from a rotating black hole in an extended gravity

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040060
Author(s):  
Vjacheslav Prokopov ◽  
Stanislav Alexeyev
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Rotating Black Hole ◽  
Extended Gravity ◽  
Extended Theories Of Gravity ◽  
Theories Of Gravity ◽  
Extended Theories

We focus on the consequences of that the Event Horizon Telescope obtained images of the black hole shadow in the center of the M87 galaxy. We show that to test extended theories of gravity the improving of the resolution by 3 orders is necessary. In addition it is demonstrated that the rotation distorts the shape of the shadow and corrections from the extended gravity may affect on this distortion.

scholarly journals Evaporation/Antievaporation and energy conditions in alternative gravity

2018 ◽  
Vol 33 (04) ◽  
pp. 1850030 ◽  
Author(s):  
Andrea Addazi
Keyword(s):  
General Relativity ◽  
Degrees Of Freedom ◽  
Energy Conditions ◽  
Raychaudhuri Equation ◽  
Bonnet Gravity ◽  
Extended Theories Of Gravity ◽  
Theories Of Gravity ◽  
Extended Theories ◽  
Alternative Gravity

We discuss the evaporation and antievaporation instabilities of Nariai solution in extended theories of gravity. These phenomena were explicitly shown in several different extensions of General Relativity, suggesting that a universal cause is behind them. We show that evaporation and antievaporation are originated from deformations of energy conditions on the Nariai horizon. Energy conditions get new contributions from the extra propagating degrees of freedom, which can provide extra focalizing or antifocalizing terms in the Raychaudhuri equation. We show the two explicit cases of [Formula: see text]-gravity and Gauss–Bonnet gravity.

scholarly journals Model-independent limits and constraints on extended theories of gravity from cosmic reconstruction techniques

2016 ◽  
Vol 2016 (12) ◽  
pp. 042-042 ◽  
Author(s):  
Álvaro de la Cruz-Dombriz ◽  
Peter K.S. Dunsby ◽  
Orlando Luongo ◽  
Lorenzo Reverberi
Keyword(s):  
Extended Theories Of Gravity ◽  
Theories Of Gravity ◽  
Model Independent ◽  
Extended Theories

scholarly journals Probing the physical and mathematical structure of f(R)-gravity by PSR J0348 + 0432

2015 ◽  
Vol 12 (04) ◽  
pp. 1550040 ◽  
Author(s):  
Mariafelicia De Laurentis ◽  
Ivan De Martino
Keyword(s):  
General Relativity ◽  
Binary Systems ◽  
Time Derivative ◽  
Mathematical Structure ◽  
Graviton Mass ◽  
Upper Limit ◽  
Extended Theories Of Gravity ◽  
Theories Of Gravity ◽  
First Time ◽  
Extended Theories

There are several approaches to extend General Relativity in order to explain the phenomena related to the Dark Matter and Dark Energy. These theories, generally called Extended Theories of Gravity, can be tested using observations coming from relativistic binary systems as PSR J0348 + 0432. Using a class of analytical f(R)-theories, one can construct the first time derivative of orbital period of the binary systems starting from a quadrupolar gravitational emission. Our aim is to set boundaries on the parameters of the theory in order to understand if they are ruled out, or not, by the observations on PSR J0348 + 0432. Finally, we have computed an upper limit on the graviton mass showing that agree with constraint coming from other observations.

Sign in / Sign up

Export Citation Format

Share Document