BH2 - Theoretical and observational studies of astrophysical black holes |
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Speaker |
Motohashi, Hayato |
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Coauthors |
Motohashi, Hayato; Minamitsuji, Masato |
| Talk Title |
General Relativity solutions in modified gravity |
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Abstract |
Since recent gravitational wave observations constrain deviation from General Relativity (GR) both on strong-field regime and cosmological scales with high accuracy, it is important to identify theories of modified gravity that intrinsically possess the same solutions as in GR among a huge number of theories. We clarify three conditions for a wide class of single-/multi-field scalar-tensor theories to allow GR solutions, i.e., solutions with the metric satisfying the Einstein equations in GR and the constant profile of the scalar fields. Our analysis applies in the presence of matter component, and any spacetime geometry including cosmological background as well as spacetime around black hole and neutron star, for the latter of which these conditions provide a necessary condition for no-hair theorem. The three conditions classify general theories of modified gravity into three classes, each of which possesses i) unique GR solutions (i.e., no-hair cases), ii) only hairy solutions (except the cases that GR solutions are realized by cancellation between singular coupling functions in the Euler-Lagrange equations), and iii) both GR and hairy solutions, for the last of which one of the two solutions may be selected dynamically. ----- Reference: Motohashi, Minamitsuji, arXiv1804.01731. |
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