MG14 - Talk detail |
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Participant |
Shapiro, Ilya | |||||||
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Institution |
Universidade Federal de Juiz de Fora Campus Universitário - Rua José Lourenço Kelmer, s/n - Juiz de Fora - Minas Gerais - - Brazil | |||||||
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Session |
DE1 |
Accepted |
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Order |
Time |
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Talk |
Oral abstract |
Title |
Renormalization and stability in higher derivative models of quantum gravity | |||||
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Abstract |
The main difficulty of perturbative quantum gravity (QG) in 4d is related to the conflict between renormalizability and unitarity. The simplest version of QG is based on General Relativity and is non-renormalizable. One can construct renormalizable and even superrenormalizable versions of QG by introducing higher derivatives, but then one has to deal with the unphysical higher derivative massive ghosts. The dynamics of metric perturbations (gravitational waves) provides certain indications that the ghosts are actually not generated below the mass threshold, which is of the Planck order of magnitude. If this is true, the higher derivative models of QG can be seen as perfect theories below the Planck cut-off. The situation is very much different is the ghost is also a tachyon. In this case there is no Planck threshold for instabilities. One can show that, for a wide class of theories and models, the transition from ghost to tachyonic ghost is imminent in the far future of the LCDM universe. |
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