Gravitational memory and soft theorems: The local perspective

De Luca, Valerio [University of Pennsylvania, Philadelphia, PA (United States)] (ORCID:0000000214445372); Khoury, Justin [University of Pennsylvania, Philadelphia, PA (United States)] (ORCID:0000000220010076); Wong, Sam S. C. [City University of Hong Kong (China)] (ORCID:0000000150549219)

doi:10.1103/gbg1-mz49

DOE OSTI · 3011547

Gravitational memory and soft theorems: The local perspective

De Luca, Valerio [University of Pennsylvania, Philadelphia, PA (United States)] (ORCID:0000000214445372)·Khoury, Justin [University of Pennsylvania, Philadelphia, PA (United States)] (ORCID:0000000220010076)·Wong, Sam S. C. [City University of Hong Kong (China)] (ORCID:0000000150549219)

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Abstract

In general relativity, gravitational memory describes the lasting change in the separation and relative velocity of freely falling detectors after the passage of gravitational waves (GWs). In this paper, we elucidate the relation between Bondi-Metzner-Sachs transformations at future null infinity and the description of gravitational memory in local synchronous coordinates, commonly used in GW detectors like LISA. We show that gravitational memory corresponds to large residual diffeomorphisms in this gauge, such as volume-preserving spatial rescalings. We reproduce the associated soft theorems for scattering amplitudes. Finally, we derive novel soft theorems for equal-time (in-in) correlation functions, which are recognized as the flat space analogues of inflationary consistency relations with a soft tensor mode. Furthermore, these relations provide a pathway toward uncovering deeper connections between gravitational memory and cosmological correlators.

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De Luca, Valerio [University of Pennsylvania, Philadelphia, PA (United States)] (ORCID:0000000214445372), Khoury, Justin [University of Pennsylvania, Philadelphia, PA (United States)] (ORCID:0000000220010076), Wong, Sam S. C. [City University of Hong Kong (China)] (ORCID:0000000150549219). 2025-07-14. Gravitational memory and soft theorems: The local perspective. https://doi.org/10.1103/gbg1-mz49

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