Can Fractional Time Operators Reproduce Gravitational-Wave Memory? A No-Go Result

Abstract

We initiate an investigation into whether fractional calculus, with its intrinsic long-tailed memory and nonlocal features, can provide a viable model for gravitational-wave memory effects. We consider two toy constructions: ($i$) a fractional modification of the linearized Einstein field equations using a sequential Caputo operator; and ($ii$) a fractionalized quadrupole formula in which the same operator acts on the source moment. Both constructions yield history-dependent responses with small memory-like offsets. However, in all cases we studied, the signal decays to zero at late times, failing to reproduce the permanent displacement predicted by General Relativity. We showed that, under asymptotic and spatial flatness of spacetime, the solutions of the proposed models decay to zero at late times when the time derivatives of the perturbed metric are temporally localized and bounded at each spatial point. Therefore, our results constitute a no-go demonstration: naive fractionalization is insufficient to model the permanent offset in the metric without explicitly building in flux-balance laws or asymptotic symmetry structure. We argue that any successful model must incorporate fractional kernels directly into the hereditary flux-balance integral of General Relativity while preserving gauge invariance and dimensional consistency. We also discuss possible connections to modified gravity and the absence of memory in spacetime with $D>4$ dimensions.