Noncommutativity in (2+1)-dimensions and the Lorentz group

TL;DR

This paper explores noncommutative models of particles in (2+1)-dimensional space-time, linking noncommutativity to Lorentz group representations and analyzing the modified Landau problem with perturbative spectrum analysis.

Contribution

It introduces a novel noncommutative framework based on Lorentz group representations and applies it to the Landau problem, revealing equivalence to models with an extra compact dimension.

Findings

No constraints between noncommutativity parameters in coordinates and momenta.

Spectrum analyzed perturbatively for small and large noncommutativity.

Models are equivalent to particles in a space with an additional compact dimension.

Abstract

In this article we considered models of particles living in a three-dimensional space-time with a nonstandard noncommutativity induced by shifting canonical coordinates and momenta with generators of a unitary irreducible representation of the Lorentz group. The Hilbert space gets the structure of a direct product with the representation space, where we are able to construct operators which realize the algebra of Lorentz transformations. We study the modified Landau problem for both Schr\"odinger and Dirac particles, whose Hamiltonians are obtained through a kind of non-Abelian Bopp's shift of the dynamical variables from the ones of the usual problem in the normal space. The spectrum of these models are considered in perturbation theory, both for small and large noncommutativity parameters. We find no constraint between the parameters referring to no-commutativity in coordinates and momenta but they rather play similar roles. Since the representation space of the unitary irreducible representations SL(2,R) can be realized in terms of spaces of square-integrable functions, we conclude that these models are equivalent to quantum mechanical models of particles living in a space with an additional compact dimension.