Local gravity and the cosmos: using local tests of modified gravity to probe cosmological physics

          @misc{ pirsa_PIRSA:07110033,
            doi = {10.48660/07110033},
            url = {https://pirsa.org/07110033},
            author = {Smith, Tristan},
            keywords = {Cosmology},
            language = {en},
            title = {Local gravity and the cosmos: using local tests of modified gravity to probe cosmological physics},
            publisher = {Perimeter Institute},
            year = {2007},
            month = {nov},
            note = {PIRSA:07110033 see, \url{https://pirsa.org}}
          }
          

Abstract

We have two strong reasons to argue that Einstein\'s theory of general relativity may be incomplete. First, given that it cannot be expressed within a consistent quantum field theory there is reason to expect higher energy corrections. Second, the observation that we are undergoing a current epoch of accelerated expansion might indicate that our understanding of gravity breaks down at the largest scales. A generic result of modified gravity is the creation of a new degree of freedom within the gravitational sector. This new degree of freedom then generically connects local physics to cosmological dynamics. I will present the results of studying two modified theories of gravity emphasizing how they bridge the gap between local and cosmological physics. First I will discuss work I have done on f(R) modified gravity theories, delineating under what conditions these theories deviate strongly from general relativity. Using these results I will talk about some recent work on attempting to detect a characteristic signature of these theories from gravitational lensing. Second I will discuss recent results on ways we may test Chern-Simons gravity (a result of the low energy effective string action) in the Solar System. Chern-Simons gravity has been identified as a candidate for leptogenesis as well as a source for circularly polarized gravitational-waves from inflation. As I will discuss, constraints to Chern-Simons gravity may improve in the near future with further observations of double pulsar systems.