Power spectra and autocovariances of level spacings beyond the Dyson conjecture

Introduced in the early days of random matrix theory, the autocovariances $\delta I_k^j=\mathrm{c}\mathrm{o}\mathrm{v}(s_j,s_{j+k})$ of level spacings $\{s_j\}$ accommodate a detailed information on correlations between individual eigenlevels. It was first conjectured by Dyson that the autocovariances of distant eigenlevels in the unfolded spectra of infinite-dimensional random matrices should exhibit a power-law decay $\delta I_k^j\approx -1\mathrm{/}\beta {\pi }^2{k}^2$, where $\beta$ is the symmetry index. In this Letter, we establish an exact link between the autocovariances of level spacings and their power spectrum, and show that, for $\beta =2$, the latter admits a representation in terms of a fifth Painlevé transcendent. This result is further exploited to determine an asymptotic expansion for autocovariances that reproduces the Dyson formula as well as provides the subleading corrections to it. High-precision numerical simulations lend independent support to our results.