Twisted Neumann--Zagier matrices

TL;DR

This paper introduces twisted Neumann--Zagier matrices, explores their symplectic properties, and demonstrates their application in defining a twisted 1-loop invariant related to hyperbolic knot complements.

Contribution

It defines a new twisted version of Neumann--Zagier matrices, details their computation from triangulations, and applies them to topological invariants of hyperbolic knots.

Findings

Twisted matrices retain symplectic properties.

They enable defining a twisted 1-loop invariant.

The invariant relates to the adjoint twisted Alexander polynomial.

Abstract

The Neumann--Zagier matrices of an ideal triangulation are integer matrices with symplectic properties whose entries encode the number of tetrahedra that wind around each edge of the triangulation. They can be used as input data for the construction of a number of quantum invariants that include the loop invariants, the 3D-index and state-integrals. We define a twisted version of Neumann--Zagier matrices, describe their symplectic properties, and show how to compute them from the combinatorics of an ideal triangulation. As a sample application, we use them to define a twisted version of the 1-loop invariant (a topological invariant) which determines the 1-loop invariant of the cyclic covers of a hyperbolic knot complement, and conjecturally equals to the adjoint twisted Alexander polynomial.