Spontaneous modulational instability of elliptic periodic waves: the soliton condensate model

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Main Authors: Agafontsev, D. S., Congy, T., El, G. A., Randoux, S., Roberti, G., Suret, P.
Format: Preprint
Published: 2024
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author Agafontsev, D. S.
Congy, T.
El, G. A.
Randoux, S.
Roberti, G.
Suret, P.
author_facet Agafontsev, D. S.
Congy, T.
El, G. A.
Randoux, S.
Roberti, G.
Suret, P.
contents We use the spectral theory of soliton gas for the one-dimensional focusing nonlinear Schrödinger equation (fNLSE) to describe the statistically stationary and spatially homogeneous integrable turbulence emerging at large times from the evolution of the spontaneous (noise-induced) modulational instability of the elliptic ``dn'' fNLSE solutions. We show that a special, critically dense, soliton gas, namely the genus one bound-state soliton condensate, represents an accurate model of the asymptotic state of the ``elliptic'' integrable turbulence. This is done by first analytically evaluating the relevant spectral density of states which is then used for implementing the soliton condensate numerically via a random N-soliton ensemble with N large. A comparison of the statistical parameters, such as the Fourier spectrum, the probability density function of the wave intensity, and the autocorrelation function of the intensity, of the soliton condensate with the results of direct numerical fNLSE simulations with dn initial data augmented by a small statistically uniform random perturbation (a noise) shows a remarkable agreement. Additionally, we analytically compute the kurtosis of the elliptic integrable turbulence, which enables one to estimate the deviation from Gaussianity. The analytical predictions of the kurtosis values, including the frequency of its temporal oscillations at the intermediate stage of the modulational instability development, are also shown to be in excellent agreement with numerical simulations for the entire range of the elliptic parameter $m$ of the initial dn potential.
format Preprint
id arxiv_https___arxiv_org_abs_2411_06922
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Spontaneous modulational instability of elliptic periodic waves: the soliton condensate model
Agafontsev, D. S.
Congy, T.
El, G. A.
Randoux, S.
Roberti, G.
Suret, P.
Pattern Formation and Solitons
We use the spectral theory of soliton gas for the one-dimensional focusing nonlinear Schrödinger equation (fNLSE) to describe the statistically stationary and spatially homogeneous integrable turbulence emerging at large times from the evolution of the spontaneous (noise-induced) modulational instability of the elliptic ``dn'' fNLSE solutions. We show that a special, critically dense, soliton gas, namely the genus one bound-state soliton condensate, represents an accurate model of the asymptotic state of the ``elliptic'' integrable turbulence. This is done by first analytically evaluating the relevant spectral density of states which is then used for implementing the soliton condensate numerically via a random N-soliton ensemble with N large. A comparison of the statistical parameters, such as the Fourier spectrum, the probability density function of the wave intensity, and the autocorrelation function of the intensity, of the soliton condensate with the results of direct numerical fNLSE simulations with dn initial data augmented by a small statistically uniform random perturbation (a noise) shows a remarkable agreement. Additionally, we analytically compute the kurtosis of the elliptic integrable turbulence, which enables one to estimate the deviation from Gaussianity. The analytical predictions of the kurtosis values, including the frequency of its temporal oscillations at the intermediate stage of the modulational instability development, are also shown to be in excellent agreement with numerical simulations for the entire range of the elliptic parameter $m$ of the initial dn potential.
title Spontaneous modulational instability of elliptic periodic waves: the soliton condensate model
topic Pattern Formation and Solitons
url https://arxiv.org/abs/2411.06922