Speaker
Dr
Emir Gumrukcuoglu
(University of Nottingham)
Description
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
be finite 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,
one can keep the Lorentz-violating terms in the matter
sector under control, although the gauge mode loops uncover
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.
