A Cosmic Glitch in Gravity

          @misc{ pirsa_PIRSA:24070070,
            doi = {10.48660/24070070},
            url = {https://pirsa.org/24070070},
            author = {Wen, Yunfei (Robin)},
            keywords = {},
            language = {en},
            title = {A Cosmic Glitch in Gravity},
            publisher = {Perimeter Institute},
            year = {2024},
            month = {jul},
            note = {PIRSA:24070070 see, \url{https://pirsa.org}}
          }
          

Abstract

We present a model that modifies general relativity on cosmological scales, specifically by having a 'glitch' in the gravitational constant between the cosmological (super-horizon) and Newtonian (sub-horizon) regimes. This gives a single-parameter extension to the standard ΛCDM model, which is equivalent to adding a dark energy component, but where the energy density of this component can have either sign. Fitting to data from the Planck satellite, we find that negative contributions are, in fact, preferred. Additionally, we find that roughly one percent weaker superhorizon gravity can somewhat ease the Hubble and clustering tensions in a range of cosmological observations. Therefore, the extra parametric freedom offered by our model deserves further exploration, and we discuss how future observations may elucidate this potential cosmic glitch in gravity, through a four-fold reduction in statistical uncertainties.