PIRSA:15110010

What if Gravity is like QCD? -- Revisiting Quadratic Gravity in Analogy with QCD

Ren, J. (2015). What if Gravity is like QCD? -- Revisiting Quadratic Gravity in Analogy with QCD. Perimeter Institute. https://pirsa.org/15110010

Ren, Jing. What if Gravity is like QCD? -- Revisiting Quadratic Gravity in Analogy with QCD. Perimeter Institute, Nov. 10, 2015, https://pirsa.org/15110010 

          @misc{ pirsa_PIRSA:15110010,
            doi = {10.48660/15110010},
            url = {https://pirsa.org/15110010},
            author = {Ren, Jing},
            keywords = {Particle Physics},
            language = {en},
            title = {What if Gravity is like QCD? -- Revisiting Quadratic Gravity in Analogy with QCD},
            publisher = {Perimeter Institute},
            year = {2015},
            month = {nov},
            note = {PIRSA:15110010 see, \url{https://pirsa.org}}
          }

Jing Ren University of Toronto

DOI 10.48660/15110010
Collection
Talk Type Scientific Series
Subject

Abstract

It has been known for a long time that quadratic gravity, which generalizes Einstein gravity with quadratic curvature terms, is renormalizable and asymptotically free in the UV.  However the theory is afflicted with a ghost problem if the perturbative spectrum is taken seriously. We explore the possibility that the dimensional scale of Einstein-Hilbert term is far smaller than the scale where the dimensionless gravitational couplings become strong. The propagation of the gravitational degrees of freedom can change character at this strong interaction scale. Lattice QCD studies show a particular suppression of gluon propagator in the IR, which removes the perturbative gluon from the physical spectrum. We propose that the same fate can apply to the spin-2 ghost. The Planck mass is associated with the strong dynamics scale below which the normal Einstein description can emerge. In this picture both the UV and IR limits have weakly coupled descriptions, similar to perturbative QCD and the chiral Lagrangian. Some implications of a small mass ratio in the theory are considered.