arXiv subjects

Andrew J. Kricker

Publications and source records attributed to Andrew J. Kricker.

3 recordsLinked to original sources

arXiv2025

On the asymptotics of the meromorphic 3D-index

In their recent work, Garoufalidis and Kashaev extended the 3D-index of an ideally triangulated 3-manifold with toroidal boundary to a well-defined topological invariant which takes the form of a meromorphic function of 2 complex variables per boundary component and which depends in addition on a quantisation parameter q. In this paper, we study asymptotics of this invariant as q approaches 1 and develop a conjectural asymptotic approximation in the form of a sum of contributions associated to conjugacy classes of certain boundary parabolic PSL(2,C) representations of the fundamental group. Furthermore, we study the coefficients appearing in these contributions, which include the hyperbolic volume, the '1-loop invariant' of Dimofte and Garoufalidis, as well as a new topological invariant of 3-manifolds with torus boundary, which we call the 'beta invariant'. The technical heart of our analysis is the expression of the state-integral of the Garoufalidis--Kashaev invariant as an integral over one connected component of the space of circle-valued angle structures introduced by Luo. Our stationary phase analysis of the asymptotics of this integral reveals many connections to the theory of angle structures and volume optimization. This investigation was motivated by extensive numerical experiments. In addition, we prove a variety of theorems about the quantities appearing in the analysis which support the overall conjectural picture.

math.GT↗

arXiv2025

Circle-valued angle structures and obstruction theory

We study spaces of circle-valued angle structures, introduced by Feng Luo, on ideal triangulations of 3-manifolds. We prove that the connected components of these spaces are enumerated by certain cohomology groups of the 3-manifold with $\mathbb{Z}_2$-coefficients. Our main theorem shows that this establishes a geometrically natural bijection between the connected components of the spaces of circle-valued angle structures and the obstruction classes to lifting boundary-parabolic $PSL(2,\mathbb{C})$-representations of the fundamental group of the 3-manifold to boundary-unipotent representations into $SL(2,\mathbb{C})$. In particular, these connected components have topological and algebraic significance independent of the ideal triangulations chosen to construct them. The motivation and main application of this study is to understand the domain of the state-integral defining the meromorphic 3D-index of Garoufalidis and Kashaev, necessary in order to classify the boundary-parabolic representations contributing to its asymptotics.

math.GT↗

arXiv2016

Random Walks on Graphs and Approximation of L2-Invariants

Right multiplication operators $R_w: l_2G \rightarrow l_2G$, $w \in \C[G]$, are interpreted as random-walk operators on labelled graphs that are analogous to Cayley graphs. Applying a generalization of the graph convergence defined by R. Grigorchuk and A. Żuk \cite{Grigorchuk_Zuk_1} gives a new proof and interpretation of a special case of W. Lück's famous Theorem on the Approximation of $l_2$-Betti numbers for countable residually finite groups. In particular, using this interpretation, the proof follows quickly from standard theorems about the weak convergence of probability measures that are characterized by their moments.

math.GR↗