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Title: Spectral fluctuations in the Sachdev-Ye-Kitaev model

Abstract

Abstract We present a detailed quantitative analysis of spectral correlations in the Sachdev-Ye-Kitaev (SYK) model. We find that the deviations from universal Random Matrix Theory (RMT) behavior are due to a small number of long-wavelength fluctuations (of the order of the number of Majorana fermions N) from one realization of the ensemble to the next one. These modes can be parameterized effectively in terms of Q-Hermite orthogonal polynomials, the main contribution being due to scale fluctuations for which we give a simple analytical estimate. Our numerical results for N = 32 show that only the lowest eight polynomials are needed to eliminate the nonuniversal part of the spectral fluctuations. The covariance matrix of the coefficients of this expansion can be obtained analytically from low-order double-trace moments. We evaluate the covariance matrix of the first six moments and find that it agrees with the numerics. We also analyze the spectral correlations in terms of a nonlinear σ-model, which is derived through a Fierz transformation, and evaluate the one and two-point spectral correlation functions to two-loop order. The wide correlator is given by the sum of the universal RMT result and corrections whose lowest-order term corresponds to scale fluctuations. However, the loopmore » expansion of the σ-model results in an ill-behaved expansion of the resolvent, and it gives universal RMT fluctuations not only for q = 4 or higher even q-body interactions, but also for the q = 2 SYK model albeit with a much smaller Thouless energy while the correct result in this case should have been Poisson statistics. In our numerical studies we analyze the number variance and spectral form factor for N = 32 and q = 4. We show that the quadratic deviation of the number variance for large energies appears as a peak for small times in the spectral form factor. After eliminating the long-wavelength fluctuations, we find quantitative agreement with RMT up to an exponentially large number of level spacings for the number variance or exponentially short times in the case of the spectral form factor.« less

Authors:
ORCiD logo [1]; ORCiD logo [1]
  1. Stony Brook Univ., NY (United States)
Publication Date:
Research Org.:
Stony Brook Univ., NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1804000
Alternate Identifier(s):
OSTI ID: 2280820
Grant/Contract Number:  
FG02-88ER40388
Resource Type:
Accepted Manuscript
Journal Name:
Journal of High Energy Physics (Online)
Additional Journal Information:
Journal Name: Journal of High Energy Physics (Online); Journal Volume: 2020; Journal Issue: 7; Journal ID: ISSN 1029-8479
Publisher:
Springer Nature
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Physics; Matrix models; Random systems; Field theories in lower dimensions; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS

Citation Formats

Jia, Yiyang, and Verbaarschot, Jacobus J. M. Spectral fluctuations in the Sachdev-Ye-Kitaev model. United States: N. p., 2020. Web. doi:10.1007/jhep07(2020)193.
Jia, Yiyang, & Verbaarschot, Jacobus J. M. Spectral fluctuations in the Sachdev-Ye-Kitaev model. United States. https://doi.org/10.1007/jhep07(2020)193
Jia, Yiyang, and Verbaarschot, Jacobus J. M. Mon . "Spectral fluctuations in the Sachdev-Ye-Kitaev model". United States. https://doi.org/10.1007/jhep07(2020)193. https://www.osti.gov/servlets/purl/1804000.
@article{osti_1804000,
title = {Spectral fluctuations in the Sachdev-Ye-Kitaev model},
author = {Jia, Yiyang and Verbaarschot, Jacobus J. M.},
abstractNote = {Abstract We present a detailed quantitative analysis of spectral correlations in the Sachdev-Ye-Kitaev (SYK) model. We find that the deviations from universal Random Matrix Theory (RMT) behavior are due to a small number of long-wavelength fluctuations (of the order of the number of Majorana fermions N) from one realization of the ensemble to the next one. These modes can be parameterized effectively in terms of Q-Hermite orthogonal polynomials, the main contribution being due to scale fluctuations for which we give a simple analytical estimate. Our numerical results for N = 32 show that only the lowest eight polynomials are needed to eliminate the nonuniversal part of the spectral fluctuations. The covariance matrix of the coefficients of this expansion can be obtained analytically from low-order double-trace moments. We evaluate the covariance matrix of the first six moments and find that it agrees with the numerics. We also analyze the spectral correlations in terms of a nonlinear σ-model, which is derived through a Fierz transformation, and evaluate the one and two-point spectral correlation functions to two-loop order. The wide correlator is given by the sum of the universal RMT result and corrections whose lowest-order term corresponds to scale fluctuations. However, the loop expansion of the σ-model results in an ill-behaved expansion of the resolvent, and it gives universal RMT fluctuations not only for q = 4 or higher even q-body interactions, but also for the q = 2 SYK model albeit with a much smaller Thouless energy while the correct result in this case should have been Poisson statistics. In our numerical studies we analyze the number variance and spectral form factor for N = 32 and q = 4. We show that the quadratic deviation of the number variance for large energies appears as a peak for small times in the spectral form factor. After eliminating the long-wavelength fluctuations, we find quantitative agreement with RMT up to an exponentially large number of level spacings for the number variance or exponentially short times in the case of the spectral form factor.},
doi = {10.1007/jhep07(2020)193},
journal = {Journal of High Energy Physics (Online)},
number = 7,
volume = 2020,
place = {United States},
year = {Mon Jul 27 00:00:00 EDT 2020},
month = {Mon Jul 27 00:00:00 EDT 2020}
}

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Works referencing / citing this record:

Towards a String Dual of SYK
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