Differential identities for the structure function of some random matrix ensembles

Abstract

The structure function of a random matrix ensemble can be specified as the covariance of the linear statistics ${\sum }_{j=1}^N{e}^{i{k}_1{\lambda }_j}$, ${\sum }_{j=1}^N{e}^{-i{k}_2{\lambda }_j}$ for Hermitian matrices, and the same with the eigenvalues ${\lambda }_j$ replaced by the eigenangles ${\theta }_j$ for unitary matrices. As such it can be written in terms of the Fourier transform of the density-density correlation ${\rho }_{(2)}$. For the circular $\beta$-ensemble of unitary matrices, and with $\beta$ even, we characterise the bulk scaling limit of ${\rho }_{(2)}$ as the solution of a linear differential equation of order $\beta +1$ -- a duality relates ${\rho }_{(2)}$ with $\beta$ replaced by $4/\beta$ to the same equation. Asymptotics obtained in the case $\beta =6$ from this characterisation are combined with previously established results to determine the explicit form of the degree 10 palindromic polynomial in $\beta /2$ which determines the coefficient of $|k{|}^{11}$ in the small $|k|$ expansion of the structure function for general $\beta >0$. For the Gaussian unitary ensemble we give a reworking of a recent derivation and generalisation, due to Okuyama, of an identity relating the structure function to simpler quantities in the Laguerre unitary ensemble first derived in random matrix theory by Brézin and Hikami. This is used to determine various scaling limits, many of which relate to the dip-ramp-plateau effect emphasised in recent studies of many body quantum chaos, and allows too for rates of convergence to be established.

32 pages; v2 minor update

References in corpus (7)

• Chaos, Complexity, and Random Matrices
• JT gravity, KdV equations and macroscopic loop operators
• Thermofield dynamics: Quantum Chaos versus Decoherence
• Vertices from replica in a random matrix theory
• Nonperturbative theory of power spectrum in complex systems
• Large $N$ expansions for the Laguerre and Jacobi $\beta$ ensembles from the loop equations
• Loop Equation Analysis of the Circular $\beta$ Ensembles

Cited by in corpus (9)

• Full counting statistics for interacting trapped fermions
• On the Spectral Form Factor for Random Matrices
• Quantifying dip-ramp-plateau for the Laguerre unitary ensemble structure function
• The classical $\beta$-ensembles with $\beta$ proportional to $1/N$: from loop equations to Dyson's disordered chain
• Dip-ramp-plateau for Dyson Brownian motion from the identity on $U(N)$
• No-resonance conditions, random matrices, and quantum chaotic models
• Hierarchical analytical approach to universal spectral correlations in Brownian Quantum Chaos
• Statistics of the Random Matrix Spectral Form Factor
• Topological gravity for arbitrary Dyson index