scholarly journals Precision cosmology in modified and extended theories of gravity: An insightful test

2021 ◽  
Author(s):  
Celia Escamilla‐Rivera
Keyword(s):  
Extended Theories Of Gravity ◽  
Theories Of Gravity ◽  
Extended Theories ◽  
Precision Cosmology

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
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