Non-linear gravitational waves in Horndeski gravity

          @misc{ pirsa_PIRSA:24070063,
            doi = {10.48660/24070063},
            url = {https://pirsa.org/24070063},
            author = {},
            keywords = {},
            language = {en},
            title = {Non-linear gravitational waves in Horndeski gravity},
            publisher = {Perimeter Institute},
            year = {2024},
            month = {jul},
            note = {PIRSA:24070063 see, \url{https://pirsa.org}}
          }
          

Abstract

The non-linear dynamics of gravitational wave propagation in spacetime can contain drastic new phenomenology that is absent from the linearised theory. In this talk, I will probe the non-linear radiative regime of Horndeski gravity by making use of disformal field redefinition. I will discuss how disformal transformations alter the properties of congruences of geodesics and in particular how they can generate disformal gravitational waves at the fully non-linear level. I will illustrate this effect by presenting a new exact radiative solution in Horndeski gravity describing a scalar pulse. Analysing the non-linear dynamics of this new radiative solution will show that it contains tensorial gravitational waves generated by a purely time-dependent scalar monopole. This intriguing result is made possible by the higher-order nature of Horndeski gravity.