REMINDER - High Energy Physics Seminar TOMORROW - Porrati

[HECAP - Margherita Di Giovannantonio]

*_HIGH ENERGY PHYSICS SEMINARS_**__*

*/!!Please note unusual venue!!/*



*Thursday, 16 April *2026, at *16:00* - *_Euler Lecture 
Hall_***-*https://indico.ictp.it/event/11301/*

Massimo Porrati (New York University)


*“Supertranslations, Angular Momentum, and Covariance in 4D 
Asymptotically Flat Space"*
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_Abstract_

This talk reviews some aspects of the "angular momentum problem" in 
general relativity as well as of old and new results in the search for 
covariant and supertranslation-invariant formulas for the flux of 
angular momentum and other Lorentz charges in asymptotically flat 
spacetimes. It addresses in particular three problems with all existing 
solutions:
1) Supertranslation-invariance and covariance imply invariance under 
spacetime translations;
2) the flux depends on redundant auxiliary degrees of freedom that 
cannot be set to zero in all Lorentz frames without breaking Lorentz 
covariance;
3) supertranslation-invariant Lorentz charges do not generate the 
transformations of the Bondi mass aspect implied by the isometries of 
the asymptotic metric.
The resolution of these problems leads to new, covariant formulas for 
the fluxes that make explicit the choice of reference frame underpinning 
seemingly unambiguous results presented in the current literature. This 
choice will be described in some detail and an elementary method for 
measuring the rotational part of the angular momentum aspect will be 
presented.

To attend via _*Zoom*_, please *_register_* here:
https://zoom.us/meeting/register/saA-11bfRBupGr3Zz6MvRQ