Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2109.04296

A new integrable model of long wave-short wave interaction and linear stability spectra

Marcos Caso-Huerta·Antonio Degasperis·Sara Lombardo·Matteo Sommacal
View original source ↗Read source document ↗Export metadata ↓

Abstract

We consider the propagation of short waves which generate waves of much longer (infinite) wave-length. Model equations of such long wave-short wave resonant interaction, including integrable ones, are well-known and have received much attention because of their appearance in various physical contexts, particularly fluid dynamics and plasma physics. Here we introduce a new long wave-short wave integrable model which generalises those first proposed by Yajima-Oikawa and by Newell. By means of its associated Lax pair, we carry out the linear stability analysis of its continuous wave solutions by introducing the stability spectrum as an algebraic curve in the complex plane. This is done starting from the construction of the eigenfunctions of the linearised long wave-short wave model equations. The geometrical features of this spectrum are related to the stability/instability properties of the solution under scrutiny. Stability spectra for the plane wave solutions are fully classified in the parameter space together with types of modulational instabilities.

Explore related subjects

nlin.SImath-phmath.APmath.MPphysics.flu-dyn

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Marcos Caso-Huerta, Antonio Degasperis, Sara Lombardo, Matteo Sommacal. 2021-09-09. A new integrable model of long wave-short wave interaction and linear stability spectra. https://doi.org/10.1098/rspa.2021.0408

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Geometric, algebraic and analytic properties of $\mathrm{al}_{ab}$ function for hyperelliptic curves of genus $g$

In this paper, we investigate the geometric, algebraic and analytic properties of the hyperelliptic $\mathrm{al}_{ab}$ functions of a hyperelliptic curve $X$ with genus $g$ as the $\mathrm{al}_{ab}$ functions together with the $\mathrm{al}_a$ functions are a generalization of the Jacobi elliptic $\mathrm{sn}$, $\mathrm{cn}$, and $\mathrm{dn}$ functions. We then demonstrate the differential identities of the $\mathrm{al}_{ab}$ function. These identities are novel integrable partial nonlinear differential equations as an extension of the differential identities in terms of the $\mathrm{al}_a$ function known as the hyperelliptic solutions of the modified Korteweg-de Vries equation. Thus, we also show that by the identities, the $\mathrm{al}_{ab}$ function is useful for expressing hyperelliptic solutions to the nonlinear Schrödinger and complex modified Korteweg-de Vries equations in an explicit form as an extension of the elliptic $\mathrm{sn}$ function solutions.

nlin.SI↗
arXiv2026

Equations of state of hydrodynamic type and particle statistics of a Dyson gas in an analytic confining potential

We investigate the equilibrium thermodynamics of a Dyson gas in connection with a set of integrable statistical mechanical observables satisfying the Toda Lattice hierarchy. We prove that in the thermodynamic limit, the integrable observables are state functions satisfying a set algebraic equations of state in closed form, obtained from direct integration of the Toda Lattice hierarchy in the continuum limit. We then explore the connection between regularity and critical behaviour of the state functions and the Dyson gas particle statistics via Monte Carlo simulations. We show that the properties of the integrable observables, such as regularity, multivaluedness, cusp singularities, carry information on the macroscopic particle statistics and its qualitative changes but with some limitations.

nlin.SI↗
arXiv2026

The Nakamura Conjecture Revisited: Toda Molecules and Stationary Axisymmetric Gravity

We revisit the Nakamura conjecture, which relates the Tomimatsu-Sato solutions of stationary axisymmetric gravity to finite Toda molecules. While the conjecture has been established partially, its general rotating sector remains an open problem. We show that the Toda determinants underlying the conjecture possess a natural weight grading. In particular, the two functions entering the Ernst potential have weights n^2 and n^2-1, and this grading extends systematically to shifted determinants labelled by partitions. In coordinates adapted to the Toda generators, each differentiation corresponds to adding one box to the associated Young diagram and increases the weight by one. The same integer n^2 also appears in the zero-order term of the Nakamura bilinear operator, revealing a compatibility between the differential equation and the determinant grading. The partition structure further explains the previously unresolved behavior of second derivatives. Repeated differentiation in one direction produces an internal sector and an external sector requiring only a one-step extension of the Wronskian hierarchy; the latter is reduced by a local three-term Pluecker relation. Thus weight grading, Young-diagram growth, Wronskian enlargement, and Pluecker reduction emerge as parts of a single determinant structure. The unit weight relation n^2 = (n^2-1) + 1 also singles out the elementary Toda seed as a natural third object, suggesting a possible route toward a genuine trilinear formulation. Although no trilinear closure is assumed here, the present construction reduces the remaining general-n Nakamura problem to definite determinant-minor identities and provides a structural framework in which such a formulation can be investigated.

nlin.SI↗