Shift operators from the simplex representation in momentum-space CFT

TL;DR

This paper introduces new integral representations for scalar n-point functions in momentum-space conformal field theory, revealing novel weight-shifting operators and enabling direct verification of conformal Ward identities.

Contribution

It derives explicit parametric integral forms for n-point functions, connects them to graph polynomials and electrical network analogies, and uncovers new weight-shifting operators in momentum-space CFT.

Findings

Expressible graph polynomials via Laplacian minors

New weight-shifting operators connecting different dimensions

Direct proof of conformal Ward identities

Abstract

We derive parametric integral representations for the general $n$-point function of scalar operators in momentum-space conformal field theory. Recently, this was shown to be expressible as a generalised Feynman integral with the topology of an $(n-1)$-simplex, featuring an arbitrary function of momentum-space cross ratios. Here, we show all graph polynomials for this integral can be expressed in terms of the first and second minors of the Laplacian matrix for the simplex. Computing the effective resistance between nodes of the corresponding electrical network, an inverse parametrisation is found in terms of the determinant and first minors of the Cayley-Menger matrix. These parametrisations reveal new families of weight-shifting operators, expressible as determinants, that connect $n$-point functions in spacetime dimensions differing by two. Moreover, the action of all previously known weight-shifting operators preserving the spacetime dimension is manifest. Finally, the new parametric representations enable the validity of the conformal Ward identities to be established directly, without recourse to recursion in the number of points.