Complex Eigenvalues in a pseudo-Hermitian \b{eta}-Laguerre ensemble

TL;DR

This paper studies how eigenvalues of a non-Hermitian ta-Laguerre ensemble behave under symmetry-breaking perturbations, revealing complex eigenvalue structures and their asymptotic properties.

Contribution

It provides the first analytical characterization of eigenvalue loci in a non-Hermitian ta-Laguerre ensemble, extending understanding beyond the well-studied ta-Hermite case.

Findings

Eigenvalues form balloon-like structures in the complex plane.

A finite line of real eigenvalues persists under perturbation.

Asymptotic analysis matches numerical simulations.

Abstract

Non-Hermitian PT-symmetric models have been extensively studied in recent years. Following the seminal work that reduced classical random matrix ensembles to a tridiagonal form, several efforts have aimed to generalize this framework to non-Hermitian extensions of the so-called \b{eta}-ensembles. In particular, while the transition of eigenvalues from the real axis to the complex plane has been well characterized for the \b{eta}-Hermite ensemble under symmetry breaking, the behavior of the \b{eta}-Laguerre ensemble in a similar non-Hermitian setting remains less understood. In this work, we investigate an ensemble of unstable matrices isospectral to the \b{eta}-Laguerre ensemble. Introducing a small non-Hermitian perturbation breaks the symmetry and drives the eigenvalues into the complex plane. We derive analytical expressions for the loci of complex-conjugate eigenvalue pairs, which organize into a balloon-like structure in the complex plane, followed by a discrete finite line of real eigenvalues. The asymptotic behavior of these eigenvalues is analyzed in the large matrix-size limit, and our theoretical predictions are supported by numerical simulations.