Folding to the Bessel-Clifford system, and Equivariant Topological Recursion

Abstract

We study the interplay between symmetry reductions of meromorphic connections, folding, and topological recursion. As a motivating example, we realize the Bessel-Clifford system as a folding of a symmetry-invariant subspace of the $0-$member of the Painlevé IV hierarchy. We introduce equivariant topological recursion for spectral curves with a Klein four-group $\mathbb Z_2\times\mathbb Z_2$ symmetry and prove that the corresponding equivariant correlators can be folded to the ordinary topological recursion correlators on the quotient spectral curve. We further establish the compatibility of this folding with the associated wave functions and quantum curves. In the Bessel-Clifford example, this yields an explicit relation between the equivariant and folded wave functions and recovers the corresponding quantum curve reduction. These results provide a framework for relating symmetry reductions of integrable systems to folding operations in topological recursion.