Computing the twisted $L^2$-Euler characteristic

Abstract

We present an algorithm that computes Friedl and Lück’s twisted $L^2$-Euler characteristic for a suitable CW complex, employing Oki’s matrix expansion algorithm to indirectly evaluate the Dieudonné determinant. The algorithm needs to run for an extremely long time to certify its outputs, but a truncated, human-assisted version produces very good results in many cases, such as hyperbolic link complements, closed census $3$-manifolds, free-by-cyclic groups, and higher-dimensional examples, such as the fiber of the Ratcliffe–Tschantz manifold.