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Spectral form factor and energy correlations in banded random matrices

T0 review · 3 major / 5 minor · reviewed 2026-08-09 · deepseek-v4-flash

Pith's one-line read Nonergodic banded random matrices keep weak long-range energy correlations, so the spectral form factor retains its correlation hole while its ramp-onset and relaxation times shrink with bandwidth.

desk verdict Solid numerical SFF characterization of BRMs with a real caveat: the timescales come from a fitted ansatz, not from the ensemble, so the decrease with bandwidth is not yet an asymptotic result. read the letter →

arxiv 2502.02648 v2 pith:XO2VH4S6 submitted 2025-02-04 cond-mat.dis-nn quant-ph

classification cond-mat.dis-nnquant-ph MSC 15B5282B4481Q50
keywords bandedrandommatricesspectralformfactornonergodicphaselong-rangeenergycorrelationsAltshuler-Shklovskiistatisticslevelnumbervariancepowerspectrumofnoisecorrelationhole
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

Banded random matrices interpolate between fully chaotic and Poisson spectra as their bandwidth shrinks. This paper shows that in the nonergodic phase, where nearest-neighbor levels obey Poisson statistics and short-range correlations are absent, weak long-range energy correlations nevertheless survive. The spectral form factor—the Fourier transform of the energy-level density, a standard time-domain probe of level correlations—therefore still develops a dip-ramp-plateau correlation hole, and its two defining timescales both shrink as the bandwidth is reduced. A semi-analytical expression for the spectral form factor, combining a fitted two-level correlation function with a density of states that interpolates between Gaussian and semicircle, reproduces numerics across all bandwidths. If correct, this means correlations usually attributed to quantum chaos can appear in systems whose local level statistics look integrable, and their timescales depend on bandwidth in the opposite way to disordered many-body systems.

What carries the argument

The central object is the two-level form factor $b_2(\tau)$, the Fourier transform of the pair correlation of unfolded eigenvalues, which controls the correlation hole in the spectral form factor. For banded random matrices the paper proposes the ansatz $b_2(\tau)=b_2^{\rm GOE}(\tau)+f(\tau)e^{-\tau/\eta}$ with $f(\tau)=a(\tau+b)(c-\tau)$ and fitted parameters, and combines it with a density of states interpolating between Gaussian and semicircle [Eq. (10)] in the standard spectral form factor decomposition to obtain Eq. (16). The deviation of $b_2$ from $b_2^{\rm GOE}$ sets $t_{\rm dip}$, while the exponential suppression sets $t_{\rm R}$, which is how the paper arrives at its main timescale result.

What would settle it

Directly measure $t_{\rm dip}$ and $t_{\rm R}$ at fixed $\gamma<1$ for growing $N$ with independent numerics that do not assume Eq. (15); if the dip time grows with $N$, or if the correlation hole depth vanishes as $N\to\infty$, the central claim is wrong. Likewise, if the large-window level number variance drifts from $\Sigma^2\propto\sqrt{\Delta E}$ toward $\Sigma^2\propto\Delta E$ as $N$ grows, the claimed persistence of weak long-range correlations fails.

Watch

Extended reading notes

Core claim

On the paper's own terms, the central discovery is that the nonergodic phase of banded random matrices is not correlation-free: even though the nearest-neighbor spacing distribution tends to the Poisson form as $N\to\infty$, the level number variance crosses from $\Sigma^2(\Delta E)=\Delta E$ below the Thouless energy to the Altshuler–Shklovskii law $\Sigma^2(\Delta E)\propto\sqrt{\Delta E}$ above it, for $0<\gamma<1$. These weak long-range correlations are sufficient to create a dip-ramp-plateau correlation hole in the spectral form factor, and because they weaken as $\gamma$ decreases, both the ramp-onset time $t_{\rm dip}$ and the relaxation time $t_{\rm R}$ decrease, merging at the Poisson limit $\gamma=0$. The paper derives a semi-analytical expression for the full spectral form factor evolution, and shows that the high-frequency exponent of the power spectrum of level fluctuations takes the values $2$, $3/2$, and $1$ in the nonergodic, critical, and ergodic phases, respectively.

Load-bearing premise

The shrinking-timescale predictions rest on the assumed pair-correlation curve in Eq. (15), whose parameters are fitted to numerical data at each bandwidth rather than derived from the banded-matrix ensemble; if the true curve differs, the trend could disappear.

Editorial extensions

If this is right

  • The dip-ramp-plateau correlation hole should be observable in the spectral form factor of any banded-random-matrix-like system in the nonergodic phase, even where the level spacing distribution is Poisson.
  • The onset and relaxation times of the correlation hole decrease monotonically as the bandwidth is reduced, and collapse onto the Poisson relaxation time at $\gamma=0$.
  • Full random matrix theory is not an appropriate reference for spectral form factor timescales in the nonergodic phase; beyond the Thouless energy the long-range statistics follow the Altshuler–Shklovskii square-root law rather than the GOE logarithmic rigidity.
  • The high-frequency exponent $\alpha$ of the power spectrum $P_k\propto k^{-\alpha}$ cleanly separates nonergodic ($\alpha=2$), critical ($\alpha=3/2$), and ergodic ($\alpha=1$) regimes.
  • The level number variance becomes system-size independent at the critical point $\gamma=1$, supporting a genuine nonergodic-ergodic transition rather than a crossover.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • Inference: because the spectral form factor is tied to the survival probability, the predicted shortening of $t_{\rm dip}$ and $t_{\rm R}$ as the bandwidth shrinks should also appear as an earlier revival of survival probability in quench dynamics of banded-random-matrix-like models; this is a direct experimental handle the paper does not work out.
  • Inference: the fitted correction $f(\tau)e^{-\tau/\eta}$ may be a finite-size stand-in for an exact two-level form factor of banded random matrices; if such an exact form exists, it would convert the fitted timescales into parameter-free predictions and likely connect them to the multifractal dimension of the eigenstates.
  • Inference: because the nonergodic phase combines Poisson short-range statistics with an Altshuler–Shklovskii long-range tail, numerical studies that use only nearest-neighbor ratios to certify integrability could misclassify such systems; a check of the level-number-variance tail or the spectral form factor correlation hole would be needed.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

3 major / 5 minor

Summary. The paper studies the spectral statistics of real symmetric banded random matrices parameterized by the bandwidth exponent γ, focusing on the ergodic (1<γ<2), critical (γ=1), and nonergodic (0<γ<1) phases. Using the level spacing distribution, spectral form factor (SFF), level number variance, and power spectrum of level fluctuations, it argues that weak long-range energy correlations persist in the nonergodic phase even though short-range correlations vanish in the thermodynamic limit. The SFF is computed semi-analytically by combining a Rosenzweig-Porter density of states with a fitted two-level form factor ansatz, and is used to extract the dip time tdip and relaxation time tR. The paper reports that, contrary to many-body localized systems, both tdip and tR decrease as the bandwidth is reduced, and that the high-frequency power-spectrum exponent distinguishes the ergodic and nonergodic phases while the low-frequency exponent tends to 3/2 in both phases.

Significance. If the central claim holds, the paper is valuable: it provides a clear numerical demonstration that banded random matrices in the nonergodic phase retain Altshuler-Shklovskii-type long-range correlations despite Poissonian short-range statistics, and it proposes a useful spectral diagnostic in the power spectrum. Important credit is due to the direct evidence in Sec. IV: the level-number-variance scaling Σ2(ΔE)∝√ΔE at large ΔE and the power-spectrum behavior Pk∝k^{-3/2} for k<kc agree with the Erdős-Knowles theorems and are independent of the SFF ansatz. The SFF analysis, however, is only as strong as the fitted two-level form factor used to produce the timescales, so the quantitative timescale claims in Fig. 5 are not yet first-principles predictions of the ensemble.

major comments (3)
  1. [Sec. III A 2, Eq. (15), Table II] The two-level form factor ansatz b2(τ)=b2^GOE(τ)+f(τ)e^{-τ/η}, with f(τ)=a(τ+b)(c−τ), is fitted separately for each γ to the same N=1024 numerical data, with four free parameters per curve. Since Eq. (16) uses this fitted function and since tdip and tR are subsequently obtained by expanding this fitted b2 (Sec. III B 1 and Sec. III B 2), the quantitative claim in Fig. 5 that tdip and tR decrease with decreasing γ is a parametric summary of the numerical b2 rather than a derivation from the BRM ensemble. The authors should either derive the functional form of b2 from the ensemble or a controlled approximation, or explicitly present the timescale results as empirical fits and test them at several system sizes.
  2. [Sec. III B, Fig. 5] The nonergodic phase approaches Poisson short-range statistics only in the N→∞ limit, as the inset of Fig. 1 shows. At N=1024 the computed b2(τ) therefore contains residual short-range level repulsion, and the fitted exponential correction in Eq. (15) may absorb that repulsion rather than the weak long-range correlations. Because no N-dependence of b2, tdip, or tR is shown for the nonergodic phase, the reported decrease of tdip and tR with decreasing γ could be a finite-size artifact. The asymptotic claim requires a scaling analysis, for example a collapse of b2(τ) or of tdip and tR at several values of N.
  3. [Sec. III B 2, Eq. (22)] The relaxation time tR is defined through a tolerance ε, but the value of ε used in Fig. 5 is not stated, and no explicit formula analogous to Eq. (22) is given for the BRM case. Since tR depends on this arbitrary threshold, the quantitative comparison with tH and the statement that tR decreases with γ need a specification of ε and a check that the trend is robust to its choice.
minor comments (5)
  1. [Sec. III A 3] The text below Eq. (20) contains a typo: “mean level spaicng” should be “mean level spacing.”
  2. [Table II] Table II lists fitted parameters only for γ=0.6, 0.7, 0.8, 1.0, 1.2, and 1.6, but Fig. 5 presents tdip and tR for the whole range 0≤γ≤2; the interpolation or separate determination of the timescales for intermediate and small γ should be clarified.
  3. [Sec. III A 1] The assumption that the Rosenzweig-Porter density of states approximates the BRM density of states is stated in the text and validated numerically in Fig. 3, but the expected accuracy of this approximation away from the bulk or for finite N is not discussed; a brief comment would help readers assess the range of validity of Eq. (10).
  4. [Sec. IV A] In Fig. 6(b), the symbols are not individually identified in the legend; identifying the γ values for each marker would improve reproducibility of the scaling analysis.
  5. [Appendix A] The reference in the sentence preceding Eq. (A2) to “Table (III)” should be “Table III,” and the displayed approximation for K(b,N) for b≪N is missing a closing parenthesis.

Circularity Check

1 steps flagged · score 6.0 of 10

The predicted decrease of tdip and tR with γ in the nonergodic phase is extracted from a per-γ fit of the two-level form factor ansatz, so the central timescale result reduces to the fitted b2(τ).

  1. fitted input called prediction [Sec. III A 2 (Eq. (15), Table II) and Secs. III B 1–2 (Eq. (16), Eq. (23), and the BRM analog of Eq. (22))]
    "Motivated by the two-level form factor of the Rosenzweig-Porter ensemble [109], we propose the following ansatz for BRM, b2(τ) = b2^GOE(τ) + f(τ)e^{−τ/η}, where f(τ) is a second order polynomial and η is a fitting parameter. ... To obtain tdip for BRMs with 0 < γ < 2, we expand the first term in Eq. (16) for large times and b2(τ) for short times ... To obtain tR for BRMs with 0 < γ < 2, we expand b2(τ) for long times, as done in the derivation of Eq. (22)."

    The b2(τ) entering Eq. (16) is not computed from the BRM ensemble; it is the ansatz of Eq. (15) with parameters η,a,b,c fitted per γ to the same N=1024 numerical SFF data (Table II, Fig. 4). The timescales tdip and tR are then derived by asymptotic expansions of this fitted function (Eq. (23) and the analog of Eq. (22)). The claimed prediction that tdip and tR decrease with decreasing γ in the nonergodic phase is therefore a parametric restatement of the fitted b2 curves, not an independent consequence of the BRM model. Since no N-scaling of b2 or of tdip,tR is shown, the trend may absorb finite-size short-range repulsion rather than the asymptotic weak long-range correlations.

full rationale

Most of the paper's content is not circular. The existence of weak long-range correlations in the nonergodic phase is independently supported by the Erdős–Knowles theorem (Ref. [53]) and by direct numerical level number variance and power-spectrum analyses (Sec. IV), neither of which depends on the fitted b2 ansatz. The density-of-states expression (Eq. (10)) is an ansatz equating BRM moments to those of the Rosenzweig-Porter ensemble, but it is checked against numerical ρ(E) and is not the source of the central quantitative claim. The circularity burden is concentrated in Sec. III B: the timescales tdip and tR, whose decrease with γ is highlighted as the key unexpected finding, are obtained by expanding Eq. (15), a two-level form-factor ansatz fitted per γ to the numerical SFF at N=1024. The reduction is explicit: Table II supplies fitting parameters, and the text states that tdip and tR are obtained by expanding b2(τ). Thus the central timescale prediction is effectively a smooth recoding of the numeric b2(τ); it is not an independent derivation. This warrants a partial circularity finding (score 6) rather than a higher one because the qualitative persistence of the correlation hole and the existence of long-range correlations have separate, non-fitted support.

Assumptions & free parameters 4 free parameters · 2 assumptions · 0 invented entities

The central derivation depends on a fitted two-level form factor ansatz with four free parameters per γ, and on the assumption that the RPE density of states approximates the BRM density of states. No new physical entities are introduced.

free parameters (4)
  • η (two-level form factor ansatz) = 0.2357 (γ=0.6); range 0.0188-0.3682 in Table II
    Fitted to numerical b2(τ) in Fig. 4; controls the exponential suppression of the non-GOE correction.
  • a (two-level form factor polynomial coefficient) = 2.4552 (γ=0.6); values in Table II
    Fitted with b and c as parameters of f(τ) = a(τ+b)(c-τ).
  • b (two-level form factor polynomial coefficient) = 0.0799 (γ=0.6); values in Table II
    Polynomial coefficient in the fit, no independent physical meaning.
  • c (two-level form factor polynomial coefficient) = 3.0127 (γ=0.6); values in Table II
    Polynomial coefficient in the fit, no independent physical meaning.
assumptions (2)
  • ad hoc to paper The Rosenzweig-Porter density of states approximates the BRM density of states when energy moments are matched.
    Sec. III A 1 and Appendix A: the BRM DOS is replaced by the RPE DOS with parameters fixed by matching the second and fourth energy moments; this is an approximation not derived from the BRM ensemble.
  • domain assumption The Altshuler-Shklovskii formula for random band matrices (Erdos-Knowles) is valid.
    The interpretation of level number variance and power spectrum relies on this external theorem (Refs. [53,124]); the paper also verifies it numerically in Fig. 6.

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Pith. "Pith review of Spectral form factor and energy correlations in banded random matrices." pith.science (2026). https://pith.science/paper/XO2VH4S6

@misc{pith2026250202648,
  author       = {Pith},
  title        = {Pith review of: Spectral form factor and energy correlations in banded random matrices},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/XO2VH4S6}},
  note         = {Machine review of arXiv:2502.02648}
}
read the original abstract

Banded random matrices were introduced as a more realistic alternative to full random matrices for describing the spectral statistics of heavy nuclei. Initially considered by Wigner, they have since become a paradigmatic model for investigating level statistics and the localization-delocalization transition in disordered quantum systems. In this work, we demonstrate that, despite the absence of short-range energy correlations, weak long-range energy correlations persist in the nonergodic phase of banded random matrices. This result is supported by our numerical and analytical studies of quantities that probe both short- and long-range energy correlations, namely, the spectral form factor, level number variance, and power spectrum. We derive the timescales for the onset of spectral correlations (ramp) and for the saturation (plateau) of the spectral form factor. Unexpectedly, we find that in the nonergodic phase, these timescales decrease as the bandwidth of the matrices is reduced. We also show that the high-frequency behavior of the power spectrum of energy fluctuations can distinguish between the nonergodic and ergodic phases of the banded random matrices.

Figures

Figures reproduced from arXiv: 2502.02648 by the authors.

Figure 1
Figure 1. FIG. 1. Level spacing distribution for BRMs of various val [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. FIG. 2. Spectral form factor for BRMs with (a) [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 4
Figure 4. FIG. 4. Two-level form factor as a function of the dimen [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
Figures from the paper (4 more)
Figure 3
Figure 3. Figure 3: FIG. 3. Density of states for BRMs with various values of [PITH_FULL_IMAGE:figures/full_fig_p005_3.png]
Figure 5
Figure 5. Figure 5: summarizes our discussions about the timescales involved in the evolution of the SFF. The Zeno time (tZeno), the time for the beginning of the ramp (tdip), the relaxation time (tR), and the Heisenberg time (tH) are shown as a function of γ for 0 ≤ γ ≤ 2. The most evi￾d…
Figure 6
Figure 6. Figure 6: FIG. 6. (a) Level number variance for various values of [PITH_FULL_IMAGE:figures/full_fig_p008_6.png]
Figure 7
Figure 7. Figure 7: FIG. 7. (a) Power-spectrum of noise for [PITH_FULL_IMAGE:figures/full_fig_p009_7.png]

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Works this paper leans on

133 extracted references · 57 canonical work pages · cited by 1 Pith paper

  1. [1]

    Density of states The density of states can be obtained in terms of the energy moments. In an ensemble of BRM, the probabil- ity density in the matrix space is normalized while the matrix norm, √ TrH 2, and the norm of the off-diagonal part have finite ensemble averages. Using the maximum entropy principle [90–93], i.e. by maximizing the Shan- non entropy...

  2. [2]

    For un- folded energy levels, Ej , the two-level cluster func- tion is denoted by Y2(E, E ′)

    Correlation hole The two-level cluster function, T2(E, E′), captures the correlations among the energy levels [3, 107]. For un- folded energy levels, Ej , the two-level cluster func- tion is denoted by Y2(E, E ′). Given the mean level spac- ing µ, the above functions are related as T2(E, E′) ≈ Y2(E, E ′)/µ2. Since Y2(E, E ′) = Y2(∆E ) [3, 108], where ∆E =...

  3. [3]

    III A 1 and for the two-level form factor in Sec

    Analytical expression: SFF Combining the results for the density of states in Sec. III A 1 and for the two-level form factor in Sec. III A 2, we evaluate Eq. (5) and obtain the following semi-analytical expression for the SFF of BRM, K (t, κ) ≈ J1 2σE t√ 1+ 1 κ 2 σ2 E t2 1+ 1 κ e σ2 E t2 1+κ − 1 N b2 t tH + 1 N , (16) where the first term comes from the F...

  4. [4]

    (16) for large times and b2(τ ) for short times, as done in the derivation of Eq

    Time for the beginning of the ramp for BRM:tdip To obtain tdip for BRMs with 0 < γ <2, we expand the first term in Eq. (16) for large times and b2(τ ) for short times, as done in the derivation of Eq. (21). The expansion of the first term in Eq. (16) for t ≫√ 1+κ−1 σE gives 1 + κ−1 3 2 e− σ2 E t2 1+κ cos2 π 4 + 2σE t√ 1+κ−1 πσ 3 Et3 , (23) which implies o...

  5. [5]

    E '2 (a) 4 51.6 4 log

    Relaxation time for BRM: tR To obtain tR for BRMs with 0 < γ <2, we expand b2(τ ) for long times, as done in the derivation of Eq. (22). For γ >1, b2(τ ) in Eq. (15) is similar tobGOE 2 (τ ) for large τ , as visible in Fig. 4, and tR ≈ tH. As γ decreases below 1 and the second term in Eq. (15) becomes dominant, the two-level form factor gets expo- nential...

  6. [6]

    E. P. Wigner, On the distribution of the roots of certain symmetric matrices, Ann. Math. 67, 325 (1958)

  7. [7]

    F. J. Dyson, The threefold way. Algebraic structure of symmetry groups and ensembles in quantum mechanics, J. Math. Phys. 3, 1199 (1962)

  8. [8]

    Mehta, Random Matrices, Pure and Applied Math- ematics (Elsevier Science, 2004)

    M. Mehta, Random Matrices, Pure and Applied Math- ematics (Elsevier Science, 2004)

Show all 133 references
  1. [9]

    T. Guhr, A. M¨ uller–Groeling, and H. A. Weidenm¨ uller, Random-matrix theories in quantum physics: Common concepts, Phys. Rep. 299, 189 (1998)

  2. [10]

    E. P. Wigner, Characteristic vectors of bordered matri- ces with infinite dimensions, Ann. Math. 62, 548 (1955)

  3. [11]

    T. A. Brody, J. Flores, J. B. French, P. A. Mello, A. Pandey, and S. S. M. Wong, Random-matrix physics: spectrum and strength fluctuations, Rev. Mod. Phys. 53, 385 (1981)

  4. [12]

    Casati, B

    G. Casati, B. Chirikov, I. Guarneri, and F. Izrailev, Quantum ergodicity and localization in conservative systems: the Wigner band random matrix model, Phys. Lett. A 223, 430 (1996)

  5. [13]

    Y. V. Fyodorov, O. A. Chubykalo, F. M. Izrailev, and G. Casati, Wigner random banded matrices with sparse structure: Local spectral density of states, Phys. Rev. Lett. 76, 1603 (1996)

  6. [14]

    D. L. Shepelyansky, Coherent propagation of two inter- acting particles in a random potential, Phys. Rev. Lett. 73, 2607 (1994)

  7. [15]

    von Oppen, T

    F. von Oppen, T. Wettig, and J. M¨ uller, Interaction- induced delocalization of two particles in a random po- tential: Scaling properties, Phys. Rev. Lett. 76, 491 (1996)

  8. [16]

    Prosen and M

    T. Prosen and M. Robnik, Energy level statistics and 12 localization in sparsed banded random matrix ensemble, J. Phys. A 26, 1105 (1993)

  9. [17]

    Janssen and K

    M. Janssen and K. Pracz, Correlated random band matrices: Localization-delocalization transitions, Phys. Rev. E 61, 6278 (2000)

  10. [18]

    B. V. Chirikov, An example of chaotic eigenstates in a complex atom, Phys. Lett. A 108, 68 (1985)

  11. [19]

    S. Iida, H. Weidenm¨ uller, and J. Zuk, Statistical scat- tering theory, the supersymmetry method and universal conductance fluctuations, Ann. Phys. 200, 219 (1990)

  12. [20]

    Y. V. Fyodorov and A. D. Mirlin, Level-to-level fluctu- ations of the inverse participation ratio in finite quasi 1D disordered systems, Phys. Rev. Lett. 71, 412 (1993)

  13. [21]

    Gefen, D

    Y. Gefen, D. Lubin, and I. Goldhirsch, Dynamics and scaling properties of localization in energy space in two- dimensional mesoscopic systems, Phys. Rev. B 46, 7691 (1992)

  14. [22]

    T. H. Seligman, J. J. M. Verbaarschot, and M. R. Zirn- bauer, Quantum spectra and transition from regular to chaotic classical motion, Phys. Rev. Lett. 53, 215 (1984)

  15. [23]

    T. H. Seligman, J. J. M. Verbaarschot, and M. R. Zirn- bauer, Spectral fluctuation properties of Hamiltonian systems: the transition region between order and chaos, J. Phys. A 18, 2751 (1985)

  16. [24]

    Richerme, Z.-X

    P. Richerme, Z.-X. Gong, A. Lee, C. Senko, J. Smith, M. Foss-Feig, S. Michalakis, A. V. Gorshkov, and C. Monroe, Non-local propagation of correlations in quantum systems with long-range interactions, Nature 511, 198 (2014)

  17. [25]

    Smith, A

    J. Smith, A. Lee, P. Richerme, B. Neyenhuis, P. W. Hess, P. Hauke, M. Heyl, D. A. Huse, and C. Mon- roe, Many-body localization in a quantum simulator with programmable random disorder, Nat. Phys. 12, 907 (2016)

  18. [26]

    L. F. Santos, M. T´ avora, and F. P´ erez-Bernal, Excited- state quantum phase transitions in many-body systems with infinite-range interaction: Localization, dynamics, and bifurcation, Phys. Rev. A 94, 012113 (2016)

  19. [27]

    Defenu, A

    N. Defenu, A. Lerose, and S. Pappalardi, Out-of- equilibrium dynamics of quantum many-body systems with long-range interactions, Phys. Rep.1074, 1 (2024)

  20. [28]

    Lerose, T

    A. Lerose, T. Parolini, R. Fazio, D. A. Abanin, and S. Pappalardi, Theory of robust quantum many-body scars in long-range interacting systems, Phys. Rev. X 15, 011020 (2025)

  21. [29]

    De Tomasi and I

    G. De Tomasi and I. M. Khaymovich, Non-hermiticity induces localization: Good and bad resonances in power-law random banded matrices, Phys. Rev. B 108, L180202 (2023)

  22. [30]

    Buijsman, M

    W. Buijsman, M. Haque, and I. M. Khaymovich, Power-law banded random matrix ensemble as a model for quantum many-body hamiltonians (2025), arXiv:2503.08825 [cond-mat.dis-nn]

  23. [31]

    Xiong, P

    W. Xiong, P. Ambichl, Y. Bromberg, B. Redding, S. Rotter, and H. Cao, Principal modes in multimode fibers: exploring the crossover from weak to strong mode coupling, Opt. Express 25, 2709 (2017)

  24. [32]

    K. C. Hegewisch and S. Tomsovic, Random matrix the- ory for underwater sound propagation, Euro. Phys. Lett. 97, 34002 (2012)

  25. [33]

    Feingold, D

    M. Feingold, D. M. Leitner, and O. Piro, Semiclassi- cal structure of Hamiltonians, Phys. Rev. A 39, 6507 (1989)

  26. [34]

    Feingold, D

    M. Feingold, D. M. Leitner, and M. Wilkinson, Spec- tral statistics in semiclassical random-matrix ensembles, Phys. Rev. Lett. 66, 986 (1991)

  27. [35]

    F. M. Izrailev, Simple models of quantum chaos: Spec- trum and eigenfunctions, Phys. Rep. 196, 299 (1990)

  28. [36]

    Pandey, A

    A. Pandey, A. Kumar, and S. Puri, Finite-range Coulomb gas models of banded random matrices and quantum kicked rotors, Phys. Rev. E96, 052211 (2017)

  29. [37]

    Pandey, A

    A. Pandey, A. Kumar, and S. Puri, Finite-range Coulomb gas models. I. Some analytical results, Phys. Rev. E 101, 022217 (2020)

  30. [38]

    Kumar, A

    A. Kumar, A. Pandey, and S. Puri, Finite-range Coulomb gas models. II. Applications to quantum kicked rotors and banded random matrices, Phys. Rev. E 101, 022218 (2020)

  31. [39]

    F. J. Dyson, The dynamics of a disordered linear chain, Phys. Rev. 92, 1331 (1953)

  32. [40]

    D. C. Herbert and R. Jones, Localized states in disor- dered systems, J. Phys. C 4, 1145 (1971)

  33. [41]

    D. J. Thouless, A relation between the density of states and range of localization for one dimensional random systems, J. Phys. C 5, 77 (1972)

  34. [42]

    Dumitriu and A

    I. Dumitriu and A. Edelman, Matrix models for beta ensembles, J. Math. Phys. 43, 5830 (2002)

  35. [43]

    A. K. Das, A. Ghosh, and I. M. Khaymovich, Robust nonergodicity of the ground states in the β ensemble, Phys. Rev. B 109, 064206 (2024)

  36. [44]

    A. K. Das and A. Ghosh, Nonergodic extended states in the β ensemble, Phys. Rev. E 105, 054121 (2022)

  37. [45]

    A. K. Das, A. Ghosh, and I. M. Khaymovich, Absence of mobility edge in short-range uncorrelated disordered model: Coexistence of localized and extended states, Phys. Rev. Lett. 131, 166401 (2023)

  38. [46]

    A. K. Das, A. Ghosh, and I. M. Khaymovich, Emer- gent multifractality in power-law decaying eigenstates (2025), arXiv:2501.17242 [cond-mat.dis-nn]

  39. [47]

    Rela˜ no, L

    A. Rela˜ no, L. Mu˜ noz, J. Retamosa, E. Faleiro, and R. A. Molina, Power-spectrum characterization of the continuous Gaussian ensemble, Phys. Rev. E77, 031103 (2008)

  40. [48]

    In this paper, we associate spectral correlations, as ob- served in full random matrices, with the notion of quan- tum chaos, although this relationship has been debated

  41. [49]

    Leviandier, M

    L. Leviandier, M. Lombardi, R. Jost, and J. P. Pique, Fourier transform: A tool to measure statistical level properties in very complex spectra, Phys. Rev. Lett. 56, 2449 (1986)

  42. [50]

    J. P. Pique, Y. Chen, R. W. Field, and J. L. Kin- sey, Chaos and dynamics on 0.5–300 ps time scales in vibrationally excited acetylene: Fourier transform of stimulated-emission pumping spectrum, Phys. Rev. Lett. 58, 475 (1987)

  43. [51]

    Guhr and H

    T. Guhr and H. Weidenmuller, Correlations in anticross- ing spectra and scattering theory. Analytical aspects, Chem. Phys. 146, 21 (1990)

  44. [52]

    Hartmann, H

    U. Hartmann, H. Weidenm¨ uller, and T. Guhr, Correla- tions in anticrossing spectra and scattering theory: Nu- merical simulations, Chem. Phys. 150, 311 (1991)

  45. [53]

    Lombardi and T

    M. Lombardi and T. H. Seligman, Universal and nonuni- versal statistical properties of levels and intensities for chaotic Rydberg molecules, Phys. Rev. A 47, 3571 (1993)

  46. [54]

    Michaille and J.-P

    L. Michaille and J.-P. Pique, Influence of experimental resolution on the spectral statistics used to show quan- 13 tum chaos: The case of molecular vibrational chaos, Phys. Rev. Lett. 82, 2083 (1999)

  47. [55]

    Schiulaz, E

    M. Schiulaz, E. J. Torres-Herrera, and L. F. Santos, Thouless and relaxation time scales in many-body quan- tum systems, Phys. Rev. B 99, 174313 (2019)

  48. [56]

    ˇSuntajs, J

    J. ˇSuntajs, J. Bonˇ ca, T. Prosen, and L. Vidmar, Quan- tum chaos challenges many-body localization, Phys. Rev. E 102, 062144 (2020)

  49. [57]

    Sierant, D

    P. Sierant, D. Delande, and J. Zakrzewski, Thouless time analysis of Anderson and many-body localization transitions, Phys. Rev. Lett. 124, 186601 (2020)

  50. [58]

    Erd˝ os and A

    L. Erd˝ os and A. Knowles, The Altshuler–Shklovskii for- mulas for random band matrices I: the unimodular case, Commun. Math. Phys. 333, 1365 (2015)

  51. [59]

    Casati, I

    G. Casati, I. Guarneri, F. M. Izrailev, L. Molinari, and K. ˙Zyczkowski, Periodic band random matrices, curva- ture, and conductance in disordered media, Phys. Rev. Lett. 72, 2697 (1994)

  52. [60]

    V. E. Kravtsov, I. M. Khaymovich, E. Cuevas, and M. Amini, A random matrix model with localization and ergodic transitions, New J. Phys.17, 122002 (2015)

  53. [61]

    Altshuler and V

    B. Altshuler and V. Kravtsov, Random Cantor sets and mini-bands in local spectrum of quantum systems, Ann. Phys. 456, 169300 (2023)

  54. [62]

    Olver and A

    S. Olver and A. Swan, Evidence of the Poisson/Gaudin- Mehta phase transition for band matrices on global scales, Random Matrices: Theory Appl. 07, 1850002 (2018)

  55. [63]

    J. M. G. G´ omez, R. A. Molina, A. Rela˜ no, and J. Re- tamosa, Misleading signatures of quantum chaos, Phys. Rev. E 66, 036209 (2002)

  56. [64]

    Spencer, Random banded and sparse matrices, inThe Oxford Handbook of Random Matrix Theory(2011)

    T. Spencer, Random banded and sparse matrices, inThe Oxford Handbook of Random Matrix Theory(2011)

  57. [65]

    Izrailev, Quantum localization and statistics of quasienergy spectrum in a classically chaotic system, Phys

    F. Izrailev, Quantum localization and statistics of quasienergy spectrum in a classically chaotic system, Phys. Lett. A 134, 13 (1988)

  58. [66]

    In the case of sparse BRMs, the Brody formula provides a better fit for the level spacing distribution [11]

  59. [67]

    Grammaticos, A

    B. Grammaticos, A. Ramani, and E. Caurier, Level spacing for band random matrices, J. Phys. A 23, 5855 (1990)

  60. [68]

    Caurier, B

    E. Caurier, B. Grammaticos, and A. Ramani, Level re- pulsion near integrability: a random matrix analogy, J. Phys. A 23, 4903 (1990)

  61. [69]

    A. K. Das and A. Ghosh, Dynamical signatures of chaos to integrability crossover in 2 × 2 generalized random matrix ensembles, J. Phys. A 56, 495003 (2023)

  62. [70]

    Casati, F

    G. Casati, F. Izrailev, and L. Molinari, Scaling prop- erties of the eigenvalue spacing distribution for band random matrices, J. Phys. A 24, 4755 (1991)

  63. [71]

    A scale invariant spectral statistics different from the semi-Poisson statistics is also observed in the power-law banded random matrices [128]

  64. [72]

    Cheon, Eigenvalue statistics of distorted random ma- trices, Phys

    T. Cheon, Eigenvalue statistics of distorted random ma- trices, Phys. Rev. Lett. 65, 529 (1990)

  65. [73]

    Y. Y. Atas, E. Bogomolny, O. Giraud, and G. Roux, Distribution of the ratio of consecutive level spacings in random matrix ensembles, Phys. Rev. Lett.110, 084101 (2013)

  66. [74]

    A. L. Corps and A. Rela˜ no, Distribution of the ratio of consecutive level spacings for different symmetries and degrees of chaos, Phys. Rev. E 101, 022222 (2020)

  67. [75]

    Hopjan and L

    M. Hopjan and L. Vidmar, Scale-invariant survival probability at eigenstate transitions, Phys. Rev. Lett. 131, 060404 (2023)

  68. [76]

    Hopjan and L

    M. Hopjan and L. Vidmar, Scale-invariant critical dy- namics at eigenstate transitions, Phys. Rev. Res. 5, 043301 (2023)

  69. [77]

    Alhassid and R

    Y. Alhassid and R. D. Levine, Spectral autocorrelation function in the statistical theory of energy levels, Phys. Rev. A 46, 4650 (1992)

  70. [78]

    del Campo, Long-time behavior of many-particle quantum decay, Phys

    A. del Campo, Long-time behavior of many-particle quantum decay, Phys. Rev. A 84, 012113 (2011)

  71. [79]

    del Campo, Exact quantum decay of an interacting many-particle system: the Calogero-Sutherland model, New J

    A. del Campo, Exact quantum decay of an interacting many-particle system: the Calogero-Sutherland model, New J. Phy. 18, 015014 (2016)

  72. [80]

    E. J. Torres-Herrera and L. F. Santos, Extended noner- godic states in disordered many-body quantum systems, Ann. Phys. (Berlin) 529, 1600284 (2017)

  73. [81]

    E. J. Torres-Herrera and L. F. Santos, Dynamical mani- festations of quantum chaos: correlation hole and bulge, Philos. Trans. Royal Soc. A 375, 20160434 (2017)

  74. [82]

    E. J. Torres-Herrera, A. M. Garc ´ ıa-Garc ´ ıa, and L. F. Santos, Generic dynamical features of quenched inter- acting quantum systems: Survival probability, density imbalance, and out-of-time-ordered correlator, Phys. Rev. B 97, 060303 (2018)

  75. [83]

    del Campo, J

    A. del Campo, J. Molina-Vilaplana, and J. Sonner, Scrambling the spectral form factor: Unitarity con- straints and exact results, Phys. Rev. D 95, 126008 (2017)

  76. [84]

    del Campo, J

    A. del Campo, J. Molina-Vilaplana, L. F. Santos, and J. Sonner, Decay of a thermofield-double state in chaotic quantum systems: From random matrices to spin sys- tems, EPJ ST 227, 247 (2018)

  77. [85]

    Z. Xu, A. Chenu, T. c. v. Prosen, and A. del Campo, Thermofield dynamics: Quantum chaos versus decoher- ence, Phys. Rev. B 103, 064309 (2021)

  78. [86]

    Lerma-Hern´ andez, D

    S. Lerma-Hern´ andez, D. Villase˜ nor, M. A. Bastarrachea-Magnani, E. J. Torres-Herrera, L. F. Santos, and J. G. Hirsch, Dynamical signatures of quantum chaos and relaxation time scales in a spin-boson system, Phys. Rev. E 100, 012218 (2019)

  79. [87]

    A. K. Das, C. Cianci, D. G. A. Cabral, D. A. Zarate-Herrada, P. Pinney, S. Pilatowsky-Cameo, A. S. Matsoukas-Roubeas, V. S. Batista, A. del Campo, E. J. Torres-Herrera, and L. F. Santos, Proposal for many- body quantum chaos detection, Phys. Rev. Res. 7, 013181 (2025)

  80. [88]

    L. K. Joshi, A. Elben, A. Vikram, B. Vermersch, V. Gal- itski, and P. Zoller, Probing many-body quantum chaos with quantum simulators, Phys. Rev. X 12, 011018 (2022)

  81. [89]

    C. B. Da˘ g, S. I. Mistakidis, A. Chan, and H. R. Sadegh- pour, Many-body quantum chaos in stroboscopically- driven cold atoms, Commun. Phys. 6, 136 (2023)

  82. [90]

    Vallejo-Fabila, A

    I. Vallejo-Fabila, A. K. Das, S. Choudhury, and L. F. Santos, Proposal for many-body quantum chaos detection with single-site measurements (2025), arXiv:2505.05572 [cond-mat.stat-mech]

  83. [91]

    H. Dong, P. Zhang, C. B. Da˘ g, Y. Gao, N. Wang, J. Deng, X. Zhang, J. Chen, S. Xu, K. Wang, Y. Wu, C. Zhang, F. Jin, X. Zhu, A. Zhang, Y. Zou, Z. Tan, Z. Cui, Z. Zhu, F. Shen, T. Li, J. Zhong, Z. Bao, H. Li, Z. Wang, Q. Guo, C. Song, F. Liu, A. Chan, L. Ying, and H. Wang, Mea...

  84. [92]

    C. Chiu, B. Misra, and E. Sudarshan, The time scale for the quantum Zeno paradox and proton decay, Phys. Lett. B 117, 34 (1982)

  85. [93]

    Leyvraz, A

    F. Leyvraz, A. Garc ´ ıa, H. Kohler, and T. H. Seligman, Fidelity under isospectral perturbations: a random ma- trix study, J. Phys. A 46, 275303 (2013)

  86. [94]

    Vallejo-Fabila, A

    I. Vallejo-Fabila, A. K. Das, D. A. Zarate-Herrada, A. S. Matsoukas-Roubeas, E. J. Torres-Herrera, and L. F. Santos, Reducing dynamical fluctuations and enforcing self-averaging by opening many-body quantum systems, Phys. Rev. B 110, 075138 (2024)

  87. [95]

    Balian, Random matrices and information theory, Il Nuovo Cimento B (1965-1970) 57, 183 (1968)

    R. Balian, Random matrices and information theory, Il Nuovo Cimento B (1965-1970) 57, 183 (1968)

  88. [96]

    E. T. Jaynes, Information theory and statistical me- chanics, Phys. Rev. 106, 620 (1957)

  89. [97]

    A. K. Das and A. Ghosh, Chaos due to symmetry- breaking in deformed Poisson ensemble, J. Stat. Mech. , 063101 (2022)

  90. [98]

    A. K. Das and A. Ghosh, Transport in deformed cen- trosymmetric networks, Phys. Rev. E 106, 064112 (2022)

  91. [99]

    Rosenzweig and C

    N. Rosenzweig and C. E. Porter, Repulsion of energy levels in complex atomic spectra, Phys. Rev. 120, 1698 (1960)

  92. [100]

    Facoetti, P

    D. Facoetti, P. Vivo, and G. Biroli, From non-ergodic eigenvectors to local resolvent statistics and back: A random matrix perspective, Europhys. Lett. 115, 47003 (2016)

  93. [101]

    Monthus, Multifractality of eigenstates in the delo- calized non-ergodic phase of some random matrix mod- els: Wigner-Weisskopf approach, J

    C. Monthus, Multifractality of eigenstates in the delo- calized non-ergodic phase of some random matrix mod- els: Wigner-Weisskopf approach, J. Phys. A: Math. Theor. 50, 295101 (2017)

  94. [102]

    Bogomolny and M

    E. Bogomolny and M. Sieber, Eigenfunction distribu- tion for the Rosenzweig-Porter model, Phys. Rev. E 98, 032139 (2018)

  95. [103]

    A. K. Das and A. Ghosh, Eigenvalue statistics for gen- eralized symmetric and hermitian matrices, J. Phys. A 52, 395001 (2019)

  96. [104]

    von Soosten and S

    P. von Soosten and S. Warzel, Non-ergodic delocaliza- tion in the Rosenzweig-Porter model, Lett. Math. Phys. 109, 905 (2019)

  97. [105]

    Buijsman and Y

    W. Buijsman and Y. B. Lev, Circular Rosenzweig- Porter random matrix ensemble, SciPost Phys. 12, 82 (2022)

  98. [106]

    Venturelli, L

    D. Venturelli, L. F. Cugliandolo, G. Schehr, and M. Tarzia, Replica approach to the generalized Rosenzweig-Porter model, SciPost Phys. 14, 110 (2023)

  99. [107]

    De Tomasi and I

    G. De Tomasi and I. M. Khaymovich, Non-Hermitian Rosenzweig-Porter random-matrix ensemble: Obstruc- tion to the fractal phase, Phys. Rev. B 106, 094204 (2022)

  100. [108]

    Sarkar, R

    M. Sarkar, R. Ghosh, and I. M. Khaymovich, Tuning the phase diagram of a Rosenzweig-Porter model with fractal disorder, Phys. Rev. B 108, L060203 (2023)

  101. [109]

    A. C. Bertuola, J. X. de Carvalho, M. S. Hussein, M. P. Pato, and A. J. Sargeant, Level density for deformations of the Gaussian orthogonal ensemble, Phys. Rev. E 71, 036117 (2005)

  102. [110]

    B¨ acker, F

    A. B¨ acker, F. Steiner, and P. Stifter, Spectral statistics in the quantized cardioid billiard, Phys. Rev. E52, 2463 (1995)

  103. [111]

    Casati and V

    G. Casati and V. Girko, Wigner’s semicircle law for band random matrices, Random Oper. & Stock. Equ. 1, 15 (1993)

  104. [112]

    Bogomolny, U

    E. Bogomolny, U. Gerland, and C. Schmit, Short-range plasma model for intermediate spectral statistics, Eur. Phys. J. B 19, 121 (2001)

  105. [113]

    Buijsman, V

    W. Buijsman, V. Cheianov, and V. Gritsev, Sensitivity of the spectral form factor to short-range level statistics, Phys. Rev. E 102, 042216 (2020)

  106. [114]

    Pandey, Brownian-motion model of discrete spectra, Chaos, Solitons & Fractals 5, 1275 (1995)

    A. Pandey, Brownian-motion model of discrete spectra, Chaos, Solitons & Fractals 5, 1275 (1995)

  107. [115]

    E. J. Torres-Herrera and L. F. Santos, Local quenches with global effects in interacting quantum systems, Phys. Rev. E 89, 062110 (2014)

  108. [116]

    E. J. Torres-Herrera and L. F. Santos, Nonexponential fidelity decay in isolated interacting quantum systems, Phys. Rev. A 90, 033623 (2014)

  109. [117]

    T´ avora, E

    M. T´ avora, E. J. Torres-Herrera, and L. F. Santos, Inevitable power-law behavior of isolated many-body quantum systems and how it anticipates thermalization, Phys. Rev. A 94, 041603 (2016)

  110. [118]

    L. A. Khalfin, Contribution to the decay theory of a quasi-stationary state, Sov. Phys. JETP 6, 1053 (1958)

  111. [119]

    T´ avora, E

    M. T´ avora, E. J. Torres-Herrera, and L. F. Santos, Power-law decay exponents: A dynamical criterion for predicting thermalization, Phys. Rev. A 95, 013604 (2017)

  112. [120]

    A. M. Garc ´ ıa-Garc ´ ıa and J. J. M. Verbaarschot, Spec- tral and thermodynamic properties of the Sachdev-Ye- Kitaev model, Phys. Rev. D 94, 126010 (2016)

  113. [121]

    D. J. Thouless, Electrons in disordered systems and the theory of localization, Physics Reports 13, 93 (1974)

  114. [122]

    Altshuler and B

    B. Altshuler and B. Shklovskii, Repulsion of energy lev- els and conductivity of small metal samples, Zh. Eksp. Teor. Fiz. 91, 220 (1986)

  115. [123]

    Altshuler, I

    B. Altshuler, I. K. Zharekeshev, S. Kotochigova, and B. Shklovskii, Repulsion between energy levels and the metal-insulator transition, Zh. Eksp. Theor. Fiz.94, 343 (1988)

  116. [124]

    C. L. Bertrand and A. M. Garc ´ ıa-Garc ´ ıa, Anomalous thouless energy and critical statistics on the metallic side of the many-body localization transition, Phys. Rev. B 94, 144201 (2016)

  117. [125]

    Serbyn, Z

    M. Serbyn, Z. Papi´ c, and D. A. Abanin, Thouless energy and multifractality across the many-body localization transition, Phys. Rev. B 96, 104201 (2017)

  118. [126]

    Sutradhar, S

    J. Sutradhar, S. Mukerjee, R. Pandit, and S. Baner- jee, Transport, multifractality, and the breakdown of single-parameter scaling at the localization transition in quasiperiodic systems, Phys. Rev. B 99, 224204 (2019)

  119. [127]

    Sierant and J

    P. Sierant and J. Zakrzewski, Level statistics across the many-body localization transition, Phys. Rev. B 99, 104205 (2019)

  120. [128]

    Y. V. Fyodorov and A. D. Mirlin, Scaling properties of localization in random band matrices: A σ-model approach, Phys. Rev. Lett. 67, 2405 (1991)

  121. [129]

    Erd˝ os and A

    L. Erd˝ os and A. Knowles, The Altshuler–Shklovskii for- mulas for random band matrices II: the general case, Ann. Henri Poincar´ e16, 709 (2015)

  122. [130]

    Rela˜ no, J

    A. Rela˜ no, J. M. G. G´ omez, R. A. Molina, J. Retamosa, and E. Faleiro, Quantum chaos and 1 /f noise, Phys. Rev. Lett. 89, 244102 (2002)

  123. [131]

    Faleiro, J

    E. Faleiro, J. M. G. G´ omez, R. A. Molina, L. Mu˜ noz, A. Rela˜ no, and J. Retamosa, Theoretical derivation of 1/f noise in quantum chaos, Phys. Rev. Lett.93, 244101 (2004). 15

  124. [132]

    Riser, V

    R. Riser, V. A. Osipov, and E. Kanzieper, Power spec- trum of long eigenlevel sequences in quantum chaotic systems, Phys. Rev. Lett. 118, 204101 (2017)

  125. [133]

    Varga and D

    I. Varga and D. Braun, Critical statistics in a power- law random-banded matrix ensemble, Phys. Rev. B 61, R11859 (2000)

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