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High Energy Theory artwork
October 2, 20232:00 pm – 3:00 pm (CDT)

A Lorentz-covariant and Supertranslation-invariant Formula for the Angular Momentum in 4D Asymptotically Flat Space


Massimo Porrati (New York University)



Mitchell Institute for Fundamental Physics & Astronomy

College Station, Texas 77843

Event Details

The angular momentum radiated in gravitational scattering can be changed by performing a supertranslation of the asymptotic metric, i.e. by adding radiation with infinite wavelength to the metric. This puzzling property can be avoided by adopting a supertranslation -invariant definition of the angular momentum flux in general relativity. None of the definitions for the angular momentum flux in terms of asymptotic data currently available in the literature is entirely satisfactory. In particular, to make the existing formulas Lorentz-covariant and in agreement with perturbative scattering calculations, some subtleties previously ignored in the literature have to be addressed. In this talk I will address those subtleties and present a supertranslation-invariant and Lorentz-covariant definition of the angular momentum and the angular momentum flux radiated during gravitational scattering. This definition uses only asymptotic metric data and reproduces the flux necessary to obtain known radiation reaction effects. The formula has an appealing physical interpretation, it extends to Lorentz boost charges and their flux, and agrees with other existing definitions in appropriate reference frames.

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