On the hyperbolic Bloch transform

TL;DR

This paper introduces the hyperbolic Bloch transform, a mathematical tool inspired by hyperbolic crystal physics, proving its key properties and connecting it to geometric structures on hyperbolic surfaces.

Contribution

It develops the hyperbolic Bloch transform, proves its injectivity and asymptotic unitarity, and links it to geometric bundles over hyperbolic surfaces, advancing the mathematical framework for hyperbolic crystal analysis.

Findings

Hyperbolic Bloch transform is injective.

Transform is asymptotically unitary.

Connects wave functions to flat bundle sections.

Abstract

Motivated by recent theoretical and experimental developments in the physics of hyperbolic crystals, we study the noncommutative Bloch transform of Fuchsian groups that we call the hyperbolic Bloch transform. First, we prove that the hyperbolic Bloch transform is injective and "asymptotically unitary" already in the simplest case, that is when the Hilbert space is the regular representation of the Fuchsian group, $\Gamma$. Second, when $\Gamma \subset \mathrm{PSU} (1, 1)$ acts isometrically on the hyperbolic plane, $\mathbb{H}$, and the Hilbert space is $L^2 \left( \mathbb{H} \right)$, then we define a modified, geometric Bloch transform, that sends wave functions to sections of stable, flat bundles over $\Sigma = \mathbb{H} / \Gamma$ and transforms the hyperbolic Laplacian into the covariant Laplacian.