| Speaker: | A. Emir Gumrukcuoglu (U of Nottingham ) |
|---|---|
| Title: | Horava gravity: Suppressing the Lorentz violations in the matter sector |
| Date (JST): | Fri, May 29, 2015, 13:00 - 14:00 |
| Place: | Seminar Room A |
| Related File: | 1465.pdf |
| Abstract: |
Horava gravity is a carefully constructed theory which is renormalizable in the power-counting sense. As the theory is founded on an anisotropic scaling between time and space, it does not respect the local Lorentz symmetry that interchanges time and space coordinates. Instead, it has a preferred time direction allowing the high energy theory to have an improved behavior, without spoiling unitarity. A major obstacle for the theory is the restoration of Lorentz invariance at low energies in the matter sector, where constraints are very stringent. A promising mechanism, proposed by Pospelov and Shang (2010), restricts the Lorentz violations to the gravity sector at tree level and these percolate the matter sector only though graviton loops. In this set-up, a hierarchy of mass scales keeps the Lorentz-violating terms in the matter sector under control, although the vector graviton loops lead to a technical naturalness problem. A large portion of the talk will be devoted to the review of Horava gravity, with an emphasis on theoretical consistency requirements and observational constraints on the Lorentz breaking scales. I will conclude by a discussion of the mixed-derivative extension of the theory, designed to resolve the naturalness problems in the Pospelov-Shang model. |
