KAM existence conjecture for whiskered tori in the Boussinesq system

Let ω0\omega^0 be the vector of real linear frequencies of the Boussinesq system, and let X=Hρ,m(T)×Hρ,m+1(T)X=H^{\rho,m}(\mathbb T)\times H^{\rho,m+1}(\mathbb T). Fix a Diophantine exponent ν>\nu>\ell and a sufficiently large regularity exponent mm. For a positive function aa, write Ba(ε)(ω0)RB_{a(\varepsilon)}(\omega^0)\subset\mathbb R^\ell for the ball of radius a(ε)a(\varepsilon) centered at ω0\omega^0.

KAM existence conjecture. There exist three explicit functions a,bd,ba:R+R+a,b_d,b_a:\mathbb R^+\to\mathbb R^+ such that

a(s)0,bd(s),ba(s)as s0,a(s)\to0,\qquad b_d(s),b_a(s)\to\infty\quad\text{as }s\to0,

and, for sufficiently small ε\varepsilon, every ωD(b(ε),ν)Ba(ε)(ω0)\omega\in\mathcal D(b(\varepsilon),\nu)\cap B_{a(\varepsilon)}(\omega^0) admits an element KXK\in X solving the invariant-torus equation for the parametrization of the Boussinesq water-wave system. Furthermore,

Dh(b(ε),ν)Ba(ε)(ω0)Ba(ε)(ω0)1.\frac{\left|D_h(b(\varepsilon),\nu)\cap B_{a(\varepsilon)}(\omega^0)\right|}{\left|B_{a(\varepsilon)}(\omega^0)\right|}\longrightarrow1.

The claim proposes the same type of large-measure KAM family for the Boussinesq water-wave system as for the preceding equation. The supplied text gives no resolution, while the surrounding discussion describes this as a result expected for related equations.

Sources & referencesView supporting material

Primary source

Rafael de la Llave and Yannick Sire, “An a posteriori KAM theorem for whiskered tori in Hamiltonian partial differential equations with applications to some ill-posed equations”, arXiv:1602.03775 (2016).

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