AT4 - Massive gravity, Horndeski theory and other "ghost-free" models of modified gravity |
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Speaker |
Zhidkova, Sofia |
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Coauthors |
Gal'tsov, Dmitri V. |
| Talk Title |
Horndeski-minimal gravity duality and resetting Fisher solution |
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Abstract |
We consider a particular scalar-tensor Horndeski gravity in Palatini formalism as a theory with two disformally related metrics. The first metric couples to matter, while the second one gives rise to an independent connection. This theory admits an alternative interpretation as Einstein gravity with minimally coupled scalar field. This proves the absence of ghosts in the considered variant of the Palatini-Hordeski model and also gives rise to generating technique for Horndeski theory. We construct the Horndeski counterpart to Fisher-Janis-Newman-Winicour (FJNW) singular solution of the standard theory for some partiucular mass to scalar charge ratio. Surprisingly, we find that in the Horndeski setting this solution becomes fully regular. The disformal transformation turns the former singular FJNW horizon to the product space of the two-dimensional Minkowski space $M_{-1,1}$ and a two sphere. This sphere is spatial section of the null hypersurface, which is neither a horizon nor an infinite redshift surface, though radial geodesics take infinite coordinate time to approach it. |
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Talk view |
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