A New Way for Spacetime to Remember

Artist’s impression of a compact-binary merger producing a gravitational-wave memory signal. In theories beyond general relativity, the reconfiguration of an additional gravitational field can generate an additional permanent imprint throug
Artist’s impression of a compact-binary merger producing a gravitational-wave memory signal. In theories beyond general relativity, the reconfiguration of an additional gravitational field can generate an additional permanent imprint through an extra polarization channel. Credit: Jann Zosso

Gravitational radiation does not only pass through the Universe as oscillating ripples. Einstein’s theory of gravity predicts that the passage of gravitational radiation also leaves behind a permanent deformation of spacetime, an effect known as gravitational memory. This memory effect can be understood as a consequence of fundamental spacetime symmetries and is a promising target for future gravitational-wave detectors to observe the universal low frequency structure of gravity.

A work led by CoG Fellow Jann Zosso that was recently published in Physics Letters B shows that gravitational memory can be much richer in theories beyond general relativity. The authors identify a general mechanism by which compact-binary coalescences can generate additional gravitational memory with the potential to significantly affect the measurable signal. When a merger reconfigures the charge of an extra gravitational field, this change can leave an additional permanent imprint in the detector response through a new polarization channel of gravitational radiation.

This result shows that memory-based tests of gravity cannot, in general, be interpreted only in terms of the tensor memory predicted by general relativity. Gravitational memory offers a low-frequency probe not only of the nonlinearity of gravity, but also of what fields gravity contains in the strong-field regime of black hole and neutron star mergers.

Aug. 1, 2026, 11:13 a.m.