Probing quantum chaos through singular-value correlations in sparse non-Hermitian SYK model

TL;DR

This paper investigates the spectral properties of a sparse non-Hermitian SYK model using singular value decomposition, revealing how sparsity affects chaos indicators and potentially disrupts holographic duality.

Contribution

It introduces the analysis of singular values in non-Hermitian SYK models, showing their statistical similarity to Hermitian ensembles and how sparsity influences chaotic behavior.

Findings

Singular value statistics match Hermitian Gaussian ensembles.

Increased sparsity leads to deviation from chaotic behavior.

Disappearance of the linear ramp in the singular form factor with sparsity.

Abstract

Utilizing singular value decomposition, our investigation focuses on the spectrum of the singular values within a sparse non-Hermitian Sachdev-Ye-Kitaev (SYK) model. Unlike the complex eigenvalues typical of non-Hermitian systems, singular values are inherently real and positive. Our findings reveal a congruence between the statistics of singular values and those of the analogous Hermitian Gaussian ensembles. An increase in sparsity results in the non-Hermitian SYK model deviating from its chaotic behavior, a phenomenon precisely captured by the singular value ratios. Our analysis of the singular form factor ({\upsigma}FF), analogous to the spectral form factor (SFF) indicates the disappearance of the linear ramp with increased sparsity. Additionally, we define singular complexity, inspired by the spectral complexity in Hermitian systems, whose saturation provides a critical threshold of sparseness. Such disintegration is likely associated with the breakdown of the existing holographic dual for non-Hermitian systems.