Kinematic Flow for Banana Loops and Unparticles

Abstract

We extend kinematic flow to a class of momentum-integrated loop-level cosmological correlators: banana loops of conformally coupled scalars in power-law cosmologies and, in de Sitter, banana loops containing arbitrary mixtures of massless and conformally coupled scalars. Exploiting their dual description as tree-level exchanges of unparticles, we show that the associated correlators are described by a finite set of master integrals obeying a first-order system of differential equations. The corresponding basis is constructed from tubings of marked graphs and is distinguished by the appearance of nested tubes and an arborescence ordering of the vertices. We derive the connection matrices from four combinatorial rules---activation, merger, swap, and copy. The last two are unique to unparticle exchanges: they induce richer mixing among basis functions and introduce new kinematic letters. Our framework extends systematically to arbitrarily complicated configurations, including necklace diagrams, and establishes unparticle exchange as a distinct class of kinematic flow.

arXiv comment41 pages; v2: published version