Circular Rosenzweig-Porter random matrix ensemble
Pith reviewed 2026-05-24 13:21 UTC · model grok-4.3
The pith
A circular Rosenzweig-Porter ensemble defined by Dyson Brownian motion on the unitary group reproduces the eigenvalue and eigenstate statistics of the original ensemble.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The circular Rosenzweig-Porter ensemble is defined as the stationary measure of a Dyson Brownian motion process on the unitary group. Numerical evidence establishes that its eigenvalue spacing statistics and eigenstate fractality are controlled by a single parameter in the same way as the original Rosenzweig-Porter ensemble, allowing the new ensemble to serve as a phenomenological model for many-body localization in Floquet systems.
What carries the argument
Dyson Brownian motion process on the unitary group, which generates the ensemble and supplies the single tunable parameter that governs the statistics.
If this is right
- The ensemble supplies a minimal model for studying the many-body localization transition in time-periodic quantum systems.
- Eigenvalue statistics are expected to interpolate between Poisson and circular unitary ensemble limits as the control parameter is varied.
- Eigenstates are expected to display fractal support in the intermediate regime, matching the static case.
- The construction avoids explicit construction of a full Floquet operator while retaining the essential phenomenology.
Where Pith is reading between the lines
- Exact analytic expressions for the joint eigenvalue distribution might follow from the known stationary measure of the Brownian motion.
- The same Brownian-motion construction could be applied to orthogonal or symplectic groups to obtain analogues for other symmetry classes.
- Direct comparison of the ensemble against microscopic Floquet many-body localized Hamiltonians would test the range of parameter values where the model remains faithful.
Load-bearing premise
The stationary distribution reached by Dyson Brownian motion on the unitary group produces eigenvalue and eigenstate statistics governed by one parameter exactly as in the original Rosenzweig-Porter ensemble.
What would settle it
Direct computation of nearest-neighbor level spacings or eigenstate inverse participation ratios on large matrices sampled from the proposed ensemble that deviate from the Rosenzweig-Porter scaling for the same parameter values.
Figures
read the original abstract
The Rosenzweig-Porter random matrix ensemble serves as a qualitative phenomenological model for the level statistics and fractality of eigenstates across the many-body localization transition in static systems. We propose a unitary (circular) analogue of this ensemble, which similarly captures the phenomenology of many-body localization in periodically driven (Floquet) systems. We define this ensemble as the outcome of a Dyson Brownian motion process. We show numerical evidence that this ensemble shares some key statistical properties with the Rosenzweig-Porter ensemble for both the eigenvalues and the eigenstates.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper proposes a unitary (circular) analogue of the Rosenzweig-Porter (RP) ensemble, defined as the stationary measure of a Dyson Brownian motion process on the unitary group with a tunable drift strength. It presents numerical evidence that this ensemble reproduces key features of the original RP ensemble, including eigenvalue level statistics that interpolate between Poisson and CUE, and eigenstate properties such as inverse participation ratios and fractal dimensions that exhibit similar system-size scaling, positioning the construction as a phenomenological model for many-body localization in Floquet systems.
Significance. If the numerical similarities hold under more extensive verification, the construction supplies a single-parameter tunable model for Floquet MBL phenomenology that parallels the utility of the real RP ensemble for static systems. The dynamical definition via Dyson Brownian motion provides a constructive route to the ensemble that is independent of the target statistics, which is a methodological strength.
major comments (2)
- [Definition via Dyson Brownian motion and numerical results] The central claim that the stationary measure yields both level statistics and eigenstate fractality (IPR, D_q) controlled by a single tunable parameter in exact analogy to the real RP ensemble rests on finite-N numerics; no derivation is given showing that the DBM drift term maps onto the off-diagonal variance scaling of the original RP model (see the definition of the ensemble and the numerical comparison sections).
- [Eigenstate statistics comparison] The reported similarity in eigenstate moments is tested only for finite system sizes without an analytical argument or extrapolation establishing that the multifractal spectrum D_q matches the RP form at corresponding parameter values; this leaves the load-bearing assumption that the ensembles are controlled identically unproven beyond the simulated regime.
minor comments (2)
- The abstract and introduction would benefit from an explicit statement of the precise range of the DBM drift parameter explored and the system sizes used in the numerics.
- Notation for the tunable parameter in the circular ensemble should be clearly distinguished from the standard RP parameter to avoid reader confusion.
Simulated Author's Rebuttal
We thank the referee for the careful reading, the positive assessment of the work's potential significance, and the constructive comments. We address the major points below, clarifying the scope of our numerical study while agreeing where additional discussion is warranted.
read point-by-point responses
-
Referee: [Definition via Dyson Brownian motion and numerical results] The central claim that the stationary measure yields both level statistics and eigenstate fractality (IPR, D_q) controlled by a single tunable parameter in exact analogy to the real RP ensemble rests on finite-N numerics; no derivation is given showing that the DBM drift term maps onto the off-diagonal variance scaling of the original RP model (see the definition of the ensemble and the numerical comparison sections).
Authors: The ensemble is defined directly as the stationary measure of the Dyson Brownian motion on U(N) with drift strength γ as the single parameter. This construction is chosen because it produces a unitary ensemble that interpolates between CUE (γ=0) and a Poisson-like regime (large γ), paralleling the RP construction. We do not derive an analytical correspondence between the DBM drift and the RP off-diagonal variance; the paper presents the DBM definition as an independent, constructive route and demonstrates numerical equivalence of the resulting statistics. We will revise the definition section to explicitly state the phenomenological character of the analogy and the absence of an analytical mapping. revision: partial
-
Referee: [Eigenstate statistics comparison] The reported similarity in eigenstate moments is tested only for finite system sizes without an analytical argument or extrapolation establishing that the multifractal spectrum D_q matches the RP form at corresponding parameter values; this leaves the load-bearing assumption that the ensembles are controlled identically unproven beyond the simulated regime.
Authors: The eigenstate comparisons (IPR and D_q) are indeed performed at finite N, with scaling plots shown for several system sizes. These indicate that the fractal dimensions follow the same parameter dependence as in the RP ensemble. We do not supply an analytical proof or controlled extrapolation to N→∞. We will add a paragraph discussing finite-size effects and the numerical character of the evidence, consistent with the level of rigor used for the original RP ensemble in the MBL literature. revision: partial
- Analytical derivation mapping the DBM drift term onto the off-diagonal variance scaling of the original RP ensemble
- Rigorous analytical argument or thermodynamic-limit proof that the multifractal spectrum D_q matches the RP form
Circularity Check
No circularity; ensemble defined independently via external DBM process
full rationale
The paper explicitly defines the circular Rosenzweig-Porter ensemble as the stationary measure obtained from a Dyson Brownian motion process on the unitary group. This construction is external to the target eigenvalue and eigenstate statistics. The paper then reports numerical evidence of shared properties with the original Rosenzweig-Porter ensemble. No step in the provided text reduces any claimed property to the definition by construction, renames a fit as a prediction, or relies on load-bearing self-citation. The derivation chain is self-contained against external benchmarks.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption Dyson Brownian motion on the unitary group produces a stationary ensemble whose statistics are analogous to those of the Rosenzweig-Porter ensemble
Forward citations
Cited by 1 Pith paper
-
Probing the Chaos to Integrability Transition in Double-Scaled SYK
A first-order phase transition in the Berkooz-Brukner-Jia-Mamroud interpolating model causes chord number, Krylov complexity, and operator size to switch discontinuously from chaotic (linear/exponential) to quasi-inte...
Reference graph
Works this paper leans on
-
[1]
D. M. Basko, I. L. Aleiner, and B. L. Altshuler, Metal- insulator transition in a weakly interacting many-electron system with localized single-particle states, Ann. Phys. 321, 1126 (2006)
work page 2006
-
[2]
I. V. Gornyi, A. D. Mirlin, and D. G. Polyakov, Interact- ing Electrons in Disordered Wires: Anderson Localiza- tion and Low- T Transport, Phys. Rev. Lett. 95, 206603 (2005)
work page 2005
-
[3]
L. D’Alessio, Y. Kafri, A. Polkovnikov, and M. Rigol, From quantum chaos and eigenstate thermalization to statistical mechanics and thermodynamics, Adv. Phys. 65, 239 (2016)
work page 2016
-
[4]
D. Huse, R. Nandkishore, and V. Oganesyan, Phe- nomenology of fully many-body-localized systems, Phys. Rev. B 90, 174202 (2014)
work page 2014
-
[5]
R. Nandkishore and D. A. Huse, Many-Body Localization and Thermalization in Quantum Statistical Mechanics, Annu. Rev. Condens. Matter Phys. 6, 15 (2015)
work page 2015
-
[6]
F. Alet and N. Laflorencie, Many-body localization: An introduction and selected topics, C.R. Phys. 19, 498 (2018)
work page 2018
-
[7]
D. A. Abanin, E. Altman, I. Bloch, and M. Serbyn, Col- loquium: Many-body localization, thermalization, and entanglement, Rev. Mod. Phys. 91, 021001 (2019)
work page 2019
-
[8]
B. L. Altshuler, Y. Gefen, A. Kamenev, and L. S. Levitov, Quasiparticle Lifetime in a Finite System: A Nonpertur- bative Approach, Phys. Rev. Lett. 78, 2803 (1997)
work page 1997
-
[9]
C. Monthus and T. Garel, Many-body localization transi- tion in a lattice model of interacting fermions: Statistics of renormalized hoppings in configuration space, Phys. Rev. B 81, 134202 (2010)
work page 2010
- [10]
-
[11]
V. Ros, M. M¨ uller, and A. Scardicchio, Integrals of mo- tion in the many-body localized phase, Nucl. Phys. B 891, 420 (2015)
work page 2015
-
[12]
F. Pietracaprina, V. Ros, and A. Scardicchio, Forward approximation as a mean-field approximation for the Anderson and many-body localization transitions, Phys. Rev. B 93, 054201 (2016)
work page 2016
- [13]
- [14]
-
[15]
S. Bera, H. Schomerus, F. Heidrich-Meisner, and J. H. Bardarson, Many-Body Localization Characterized from a One-Particle Perspective, Phys. Rev. Lett. 115, 046603 (2015)
work page 2015
-
[16]
B. Villalonga, X. Yu, D. J. Luitz, and B. K. Clark, Ex- ploring one-particle orbitals in large many-body localized systems, Phys. Rev. B 97, 104406 (2018)
work page 2018
-
[17]
W. Buijsman, V. Gritsev, and V. Cheianov, Many-body localization in the Fock space of natural orbitals, Scipost Phys. 4, 038 (2018)
work page 2018
-
[18]
M. Hopjan and F. Heidrich-Meisner, Many-body local- ization from a one-particle perspective in the disor- dered one-dimensional Bose-Hubbard model, Phys. Rev. A 101, 063617 (2020)
work page 2020
- [19]
-
[20]
A. Altland and T. Micklitz, Field Theory Approach to Many-Body Localization, Phys. Rev. Lett. , 127202 (2017)
work page 2017
- [21]
-
[22]
A. De Luca, B. L. Altshuler, V. E. Kravtsov, and A. Scardicchio, Anderson Localization on the Bethe Lat- tice: Nonergodicity of Extended States, Phys. Rev. Lett. 113, 046806 (2014)
work page 2014
-
[23]
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)
work page 2015
-
[24]
K. S. Tikhonov and A. D. Mirlin, From Anderson local- ization on random regular graphs to many-body localiza- tion, Ann. Phys. 435, 168525 (2021)
work page 2021
-
[25]
N. Rosenzweig and C. E. Porter, “Repulsion of Energy Levels” in Complex Atomic Spectra, Phys. Rev. 120, 1698 (1960)
work page 1960
-
[26]
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)
work page 2016
-
[27]
K. Truong and A. Ossipov, Eigenvectors under a generic perturbation: Non-perturbative results from the random matrix approach, New J. Phys. 116, 37002 (2016)
work page 2016
-
[28]
Amini, Spread of wave packets in disordered hierar- chical lattices, Europhys
M. Amini, Spread of wave packets in disordered hierar- chical lattices, Europhys. Lett. 117, 30003 (2017)
work page 2017
-
[29]
C. Monthus, Multifractality of eigenstates in the delocal- ized non-ergodic phase of some random matrix models: Wigner–Weisskopf approach, J. Phys. A: Math. Theor. 50, 295101 (2017)
work page 2017
-
[30]
E. Bogomolny and M. Sieber, Eigenfunction distribu- tion for the Rosenzweig-Porter model, Phys. Rev. E 98, 032139 (2018)
work page 2018
-
[31]
G. De Tomasi, M. Amini, S. Bera, I. M. Khaymovich, and V. E. Kravtsov, Survival probability in General- ized Rosenzweig-Porter random matrix ensemble, SciPost Phys. 6, 014 (2019)
work page 2019
-
[32]
P. von Soosten and S. Warzel, Non-ergodic delocalization in the Rosenzweig-Porter model, Lett. Math. Phys. 109, 905 (2019)
work page 2019
-
[33]
M. Pino, J. Tabanera, and P. Serna, From ergodic to non-ergodic chaos in Rosenzweig-Porter model, J. Phys. A: Math. Theor. 52, 475101 (2019)
work page 2019
-
[34]
R. Berkovits, Super-Poissonian behavior of the Rosenzweig-Porter model in the nonergodic extended regime, Phys. Rev. B 102, 165140 (2020)
work page 2020
-
[35]
Tarzia, Many-body localization transition in Hilbert space, Phys
M. Tarzia, Many-body localization transition in Hilbert space, Phys. Rev. B 102, 014208 (2020)
work page 2020
- [36]
-
[37]
A. Lazarides, A. Das, and R. Moessner, Fate of Many- Body Localization Under Periodic Driving, Phys. Rev. Lett. 115, 030402 (2015)
work page 2015
-
[38]
D. A. Abanin, W. de Roeck, and F. Huveneers, Theory of many-body localization in periodically driven systems, Ann. Phys. 372, 1 (2016)
work page 2016
- [39]
- [40]
-
[41]
S. Roy, R. Moessner, and A. Lazarides, How periodic driving stabilizes and destabilizes Anderson localization on random trees, Phys. Rev. B 103, L100204 (2021)
work page 2021
-
[42]
F. J. Dyson, A Brownian-Motion Model for the Eigenval- ues of a Random Matrix, J. Math. Phys. 3, 1196 (1962)
work page 1962
- [43]
-
[44]
I. M. Khaymovich, V. E. Kravtsov, B. L. Altshuler, and L. B. Ioffe, Fragile extended phases in the log-normal Rosenzweig-Porter model, Phys. Rev. Research2, 043346 (2020)
work page 2020
-
[45]
G. Biroli and M. Tarzia, L´ evy-Rosenzweig-Porter random matrix ensemble, Phys. Rev. B 103, 104205 (2021)
work page 2021
-
[46]
I. M. Khaymovich and V. E. Kratsov, Dynamical phases in a “multifractal” Rosenzweig-Porter model, SciPost Phys. 11, 45 (2021)
work page 2021
-
[47]
J. N. Bandyopadhyay, J. Wang, and J. Gong, Generating a fractal butterfly Floquet spectrum in a class of driven SU (2) systems: Eigenstate statistics, Phys. Rev. E 81, 066212 (2010)
work page 2010
-
[48]
S. Ray, A. Ghosh, and S. Sinha, Drive-induced delocaliza- tion in the Aubry-Andr´ e model, Phys. Rev. E97, 010101 (2018)
work page 2018
-
[49]
S. Roy, I. M. Khaymovich, A. Das, and R. Moessner, Mul- tifractality without fine-tuning in a Floquet quasiperiodic chain, SciPost Phys. 4, 025 (2018)
work page 2018
- [50]
-
[51]
M. L. Mehta, Random Matrices, 3rd ed., Pure and Ap- 7 plied Mathematics, Vol. 142 (Elsvier, New York, 2004)
work page 2004
-
[52]
P. J. Forrester, Log-Gases and Random Matrices, London Mathematical Society Monographs, Vol. 34 (Princeton University Press, Princeton and Oxford, 2010)
work page 2010
-
[53]
A. Altland, M. Janssen, and B. Shapiro, Perturbation theory for the Rosenzweig-Porter matrix model, Phys. Rev. E 56, 1471 (1997)
work page 1997
-
[54]
V. Oganesyan and D. A. Huse, Localization of interacting fermions at high temperature, Phys. Rev. B 75, 155111 (2007)
work page 2007
-
[55]
Y. Y. Atas, E. Bogomolny, O. Giraud, and G. Roux, Dis- tribution of the Ratio of Consecutive Level Spacings in Random Matrix Ensembles, Phys. Rev. Lett.110, 084101 (2013)
work page 2013
-
[56]
E. P. Wigner, Characteristic Vectors of Bordered Matri- ces With Infinite Dimensions, Ann. Math.62, 548 (1955)
work page 1955
-
[57]
P. Jacquod and D. L. Shepelyansky, Hidden Breit-Wigner Distribution and Other Properties of Random Matrices with Preferential Basis, Phys. Rev. Lett.75, 3501 (1995)
work page 1995
-
[58]
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)
work page 1996
-
[59]
F. Borgonovi, F. M. Izrailev, L. F. Santos, and V. G. Zelevinsky, Quantum chaos and thermalization in iso- lated systems of interacting particles, Phys. Rep. 626, 1 (2016)
work page 2016
-
[60]
E. Cuevas and V. E. Kravtsov, Two-eigenfunction corre- lation in a multifractal metal and insulator, Phys. Rev. B 76, 235119 (2007)
work page 2007
-
[61]
The eigenvectors of Gaussian matrices with an external source
R. Allez, J. Bun, and J.-P. Bouchaud, The eigen- vectors of Gaussian matrices with an external source, arXiv:1412.7108v4 (2015)
work page internal anchor Pith review Pith/arXiv arXiv 2015
-
[62]
P. Bourgade and H.-T. Yau, The eigenvector moment flow and local quantum unique ergodicity, Commun. Math. Phys. 350, 231 (2017)
work page 2017
-
[63]
The set US(N) of symmetric unitary matrices of dimen- sion N is isomorphic to U(N)/O(N), where U(N) de- notes the set of imaginary unitary matrices of dimension N, and O(N) denote the set of real orthogonal matrices of dimension N. For a proof, see e.g. Proposition 2.2.4 of Ref. [52]
-
[64]
P. J. Forrester and T. Nagao, Correlations for the circu- lar Dyson Brownian motion model with Poisson initial conditions, Nucl. Phys. B 532, 733 (1998)
work page 1998
- [65]
- [66]
-
[67]
D. J. Luitz, I. M. Khaymovich, and Y. Bar Lev, Mul- tifractality and its role in anomalous transport in the disordered XXZ spin-chain, SciPost Phys. Core 2, 006 (2020)
work page 2020
-
[68]
A. G. Kutlin and I. M. Khaymovich, Emergent fractal phase in energy stratified random models, SciPost Phys. 11, 101 (2021)
work page 2021
-
[69]
A. Chan, A. De Luca, and J. T. Chalker, Solution of a Minimal Model for Many-Body Quantum Chaos, Phys. Rev. X 8, 041019 (2018)
work page 2018
-
[70]
A. Chan, A. De Luca, and J. T. Chalker, Spectral Statis- tics in Spatially Extended Chaotic Quantum Many-Body Systems, Phys. Rev. Lett. 121, 060601 (2018)
work page 2018
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.