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Shadows of rotating Hayward-de Sitter black holes with astrometric observables

Peng-Zhang He; Qi-Qi Fan; Hao-Ran Zhang; Jian-Bo DengSubjects: Physics >> Geophysics, Astronomy, and Astrophysics

Motivated by recent work on rotating black hole shadow [Phys. Rev. D101, 084029 (2020)], we investigate the shadow behaviors of rotating Hayward-de Sitter black hole for static observers at a finite distance in terms of astronomical observables. This paper uses the newly introduced distortion parameter in [arXiv:2006.00685] to describe the shadow's shape quantitatively. We show that the spin parameter would distort shadows and the magnetic monopole charge would increase the degree of deformation. At the same time, the distortion could be relieved because of the cosmological constant and the distortion would increase with the distance from the black hole. Besides, the spin parameter, magnetic monopole charge and cosmological constant increase will cause the shadow to shrink. |

The cosmological constant from space-time discreteness

Qi-Qi Fan; Cong Li; Hao-Ran Zhang; Peng-Zhang He,; Jian-Bo DengSubjects: Physics >> The Physics of Elementary Particles and Fields

We regard the background of space-time as a physical system composed of discrete volume elements at the Planck scale and get the internal energy of space-time by Debye model. A temperature-dependent minimum energy limit of the particles is proposed from the thermal motion part of the internal energy. As decreases of the temperature caused by the expansion of the universe, more and more particles would be "released" because of the change of the energy limit, we regard these new particles as a source of dark energy. The minimum energy limit also leads to a corrected number of particles in universe and a modified conservation equation. According to the modified conservation equation, an effective cosmological constant consistent with its observed value is obtained. |

[1 Pages/ 2 Totals]