The equivalence between Feynman transform and Verdier duality

TL;DR

This paper generalizes the known equivalence between dg duality and Verdier duality from cyclic operads to twisted modular operads, establishing a geometric interpretation via sheaves on moduli spaces and linking Feynman transforms with Verdier dual sheaves.

Contribution

It extends the duality correspondence to twisted modular operads and provides a geometric interpretation, also proving a previously unestablished relation between cyclic and modular operads.

Findings

Established the sheaf-theoretic correspondence for twisted modular operads.

Proved a relation between cyclic and modular operads.

Provided a new, simpler proof of the homotopy properties of Feynman transform.

Abstract

The equivalence between dg duality and Verdier duality has been established for cyclic operads earlier. We propose a generalization of this correspondence from cyclic operads and dg duality to twisted modular operads and Feynman transform. Specifically, for each twisted modular operad $\mathcal{P}$ (taking values in dg-vector spaces over a field $k$ of characteristic 0), there is a certain sheaf $\mathcal{F}$ associated with it on the moduli space of stable metric graphs such that the Verdier dual sheaf $D\mathcal{F}$ is associated with the Feynman transform $F\mathcal{P}$ of $\mathcal{P}$. In the course of the proof, we also prove a relation between cyclic operads and modular operads originally proposed in the pioneering work of Getzler and Kapranov; however, to the best knowledge of the author, no proof has been given in any literature. This geometric interpretation in operad theory is of fundamental importance. We believe this result will illuminate many aspects of the theory of modular operads and find many applications in the future. We illustrate an application of this result, giving another proof on the homotopy properties of Feynman transform, which is quite intuitive and simpler than the original proof.