An Asymptotic Framework for Gravitational Scattering


Gralla, S. (2023). An Asymptotic Framework for Gravitational Scattering. Perimeter Institute. https://pirsa.org/23050033


Gralla, Samuel. An Asymptotic Framework for Gravitational Scattering. Perimeter Institute, May. 11, 2023, https://pirsa.org/23050033


          @misc{ pirsa_PIRSA:23050033,
            doi = {10.48660/23050033},
            url = {https://pirsa.org/23050033},
            author = {Gralla, Samuel},
            keywords = {Strong Gravity},
            language = {en},
            title = {An Asymptotic Framework for Gravitational Scattering},
            publisher = {Perimeter Institute},
            year = {2023},
            month = {may},
            note = {PIRSA:23050033 see, \url{https://pirsa.org}}

Sam Gralla University of Arizona

Talk Type Scientific Series


Gravitational scattering provides valuable insight into classical dynamics and is likely of fundamental importance in quantum gravity.  However, a complete framework for gravitational scattering does not yet exist.  The lack of a clear framework hinders progress; for example, different groups have reported different results for the loss of angular momentum in post-Minkowskian scattering.  In this talk I will report on recent work 2303.17124 with Compere and Wei constructing a general framework for classical gravitational scattering of finite-sized massive bodies in four spacetime dimensions.  We formulate assumptions and definitions such that the five asymptotic regions (past/future timelike/null infinity and spatial infinity) share a single Bondi-Metzner-Sachs (BMS) group of symmetries and associated charges and derive global conservation laws stating that the total change in charge is balanced by the corresponding radiative flux.  Our assumptions are compatible with all known properties of scattering spacetimes, including certain logarithmic corrections that invalidate common falloff assumptions.  Among the new implications are rigorous definitions for quantities like initial/final spin, scattering angle, and impact parameter in multi-body spacetimes, without the use of any preferred background structure.  We show that spin is supertranslation-invariant, while impact parameter is not.  To complement these derivations I will emphasize a helpful "puzzle piece" diagram that faithfully represents all five asymptotic regions, illustrating their roles in the scattering problem.

Zoom link:  https://pitp.zoom.us/j/94358515412?pwd=cUFocVNjQ1pqUmp4MDN0RmRLbjE0QT09