Quadratic Gravity: From Weak to Strong

 

Dr Jing Ren
University of Toronto
 

13 Sep 2016 (Tuesday)
2:00 pm
IAS4042, 4/F, Lo Ka Chung Building, Lee Shau Kee Campus, HKUST

More than three decades ago, quadratic gravity was found to present a perturbative, renormalizable and asymptotically free theory of quantum gravity. Unfortunately, the theory appeared to have problems with a spin-2 ghost. In this talk, the speaker will revisit quadratic gravity in a different light by considering the case that the asymptotically free interaction flows to a strongly interacting regime. This occurs when the coefficient of the Einstein-Hilbert term is smaller than the scale that the quadratic couplings grow strong. Here QCD provides some useful insights. By pushing the analogy with QCD, she conjectures that the nonperturbative effects can remove the naive spin-2 ghost and lead to the emergence of general relativity in the IR, with the Planck mass identified as the strong gravity scale. This theory has new static spherically symmetric vacuum solutions that resemble black holes while remaining horizonless. It might be of great interests in the new era of gravitational wave astronomy.