Black hole shadow to probe modified gravity. (arXiv:2101.08261v1 [gr-qc])
<a href="http://arxiv.org/find/gr-qc/1/au:+Stepanian_A/0/1/0/all/0/1">A. Stepanian</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Khlghatyan_S/0/1/0/all/0/1">Sh. Khlghatyan</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Gurzadyan_V/0/1/0/all/0/1">V.G. Gurzadyan</a>

We study the black hole’s shadow for Schwarzschild – de Sitter and Kerr – de
Sitter metrics with the contribution of the cosmological constant Lambda.
Based on the reported parameters of the M87* black hole shadow we obtain
constraints for the $Lambda$ and show the agreement with the cosmological
data. It is shown that, the coupling of the Lambda-term with the spin
parameter reveals peculiarities for the photon spheres and hence for the
shadows. Within the parametrized post-Newtonian formalism the constraint for
the corresponding Lambda-determined parameter is obtained.

We study the black hole’s shadow for Schwarzschild – de Sitter and Kerr – de
Sitter metrics with the contribution of the cosmological constant Lambda.
Based on the reported parameters of the M87* black hole shadow we obtain
constraints for the $Lambda$ and show the agreement with the cosmological
data. It is shown that, the coupling of the Lambda-term with the spin
parameter reveals peculiarities for the photon spheres and hence for the
shadows. Within the parametrized post-Newtonian formalism the constraint for
the corresponding Lambda-determined parameter is obtained.

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