Gravity as the square of gauge theory


Borsten, L. (2021). Gravity as the square of gauge theory. Perimeter Institute for Theoretical Physics.


Borsten, Leron. Gravity as the square of gauge theory. Perimeter Institute for Theoretical Physics, Mar. 01, 2021,


          @misc{ scivideos_PIRSA:21030011,
            doi = {10.48660/21030011},
            url = {},
            author = {Borsten, Leron},
            keywords = {Mathematical physics, Particle Physics, Quantum Fields and Strings},
            language = {en},
            title = {Gravity as the square of gauge theory},
            publisher = {Perimeter Institute for Theoretical Physics},
            year = {2021},
            month = {mar},
            note = {PIRSA:21030011 see, \url{}}

Leron Borsten Heriot-Watt University

Source RepositoryPIRSA


Can gravity, in certain regards, be the `product' of two gauge theories, such as those appearing in the Standard Model? I will begin by reviewing the Bern—Carrasco—Johansson colour—kinematics duality conjecture, which implies that one can write the scattering amplitudes of Einstein-Hilbert gravity (coupled to a Kalb-Ramond 2-form and dilaton scalar) as the double copy of Yang—Mills amplitudes. Although the colour—kinematics duality, and therefore the double copy, was quickly established at the tree level, it remains a longstanding open problem at the loop level, despite highly non-trivial explicit examples. I will then describe how one can take this `gravity = gauge x gauge' amplitude paradigm `off-shell’ as a product of spacetime fields: the Yang-Mills BRST-Lagrangian itself double copies into perturbatively quantised Einstein-Hilbert gravity coupled to a Kalb-Ramond 2-form and dilaton, establishing the validity of the double copy to all orders, tree and loop. I will end by briefly discussing the homotopy algebras underpinning this result and the inclusion of supersymmetry, which reveals fascinating octonionic structures (some very well-known, others completely new) that will be the subject of Mia Hughes's talk in the following week.