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Alexander Zhiboedov is a theoretical physicist who, with Andrew Strominger, connected gravitational memory to the Soft graviton theorem. Their 2014 preprint considers arrays of detectors before and after passage of a gravitational radiation pulse near future null infinity.

The resulting relative displacement reproduces gravitational memory, while its formula is related to the low-energy limit described by the Soft graviton theorem. This unites a lasting change in detector separation with an apparently different statement about emission of very low-energy gravitons.^[ref]

Institutional profile: theory.cern/roster/zhiboedov-alexander.

Andrew Strominger studies quantum gravity, string theory and black holes. His work with Alexander Zhiboedov relates gravitational memory to the Soft graviton theorem through the behaviour of detectors and radiation near future null infinity.

A pulse need not leave only a passing oscillation: it can produce a lasting relative displacement between freely moving detectors. Their calculation links that displacement to the radiation energy flux, making a measurable classical effect part of a broader relationship with low-energy quantum emission.^[ref]

Institutional profile: www.physics.harvard.edu/people/facpages/strominger.

The Bondi shear is the leading trace-free angular distortion in an asymptotically flat spacetime described by Bondi-Sachs coordinates. In a common expansion, the angular metric is $h_{AB}=q_{AB}+C_{AB}/r+O(r^{-2})$, with $q^{AB}{C}_{AB}=0$.

Its retarded-time derivative determines the Bondi news function, with normalization depending on convention. The distinction matters: a nonzero but time-independent shear need not represent ongoing radiation, while changing shear describes radiative degrees of freedom. Changes between early and late configurations are also connected with gravitational memory.^[ref]

Gravitational memory is a persistent change in the relative configuration of freely falling bodies after a gravitational-wave burst has passed. In the weak-field transverse-traceless description, an initially separated pair obeys $\Delta {\xi }^i\simeq \frac{1}{2}\Delta h_{ij}^{\mathrm{TT}}{\xi }^j$. A nonzero net strain change leaves a displacement rather than only a temporary oscillation.

Memory can arise from changes in the motion of material sources and from the energy carried away by radiation itself. The latter contribution reflects the nonlinear gravitational role of wave energy. Distinguishing this slow or step-like response from detector drift requires more than identifying an oscillatory waveform.^[ref]