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Geometry of In-In Correlators
Phys. Rev. Lett. 137, 161603 – Published 14 October, 2026
DOI: https://doi.org/10.1103/39dm-2rsw
Abstract
We introduce a family of polytopes—in-in zonotopes—whose boundary structure organizes the contributions to scalar equal-time correlators in flat space computed via the in-in formalism. We provide explicit Minkowski sum and facet descriptions of these polytopes, and show that their boundaries factorize into products of graphical zonotopes and lower-dimensional in-in zonotopes, thereby mimicking the factorization structure of the correlators themselves. Evaluating their canonical forms at the origin—equivalently, calculating the volume of the dual polytope—reproduces the correlator. Finally, in a simple example, we show that the wave function decomposition of the correlator corresponds to a subdivision of the dual polytope.
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