On the integrability problem of a continuous Toda system

In this paper we discuss the integrability problem for a continuous Toda system, which is widely applicable in many branches of theoretical and mathematical physics and mechanics.Dedicated to the memory of Mikhail Constantinovich PolivanovInstitute of High-Energy Physics. Published in Teoreticheskaya i Matematicheskaya Fizika, Vol. 92, No. 3, pp. 457–465, September, 1992.     

Analytical integrability of the Rikitake system

In this paper, we study the first integrals of the Rikitake system $$\dot{x} = -\mu x + yz, \quad \dot{y} = -\mu y + x (z-a), \quad \dot{z} = 1-xy,$$ that can be described by formal power series when the system has singular points.     

On integrability of the Euler-Poisson equations

We consider a special case of the Euler-Poisson system of equations, describing the motion of a rigid body around a fixed point. We find 44 sets of stationary solutions near which the system is locally integrable. Ten of them are real. We also study the number of these complex stationary solutions in 3-dimensional invariant manifolds of the system. We find that the number is 4, 2, 1, or 0. __________ Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 13, No. 1, pp. 45–59, 2007.     

On the integrability of Lie subalgebroids

Let G be a Lie groupoid with Lie algebroid g. It is known that, unlike in the case of Lie groups, not every subalgebroid of g can be integrated by a subgroupoid of G. In this paper we study conditions on the invariant foliation defined by a given subalgebroid under which such an integration is possible. We also consider the problem of integrability by closed subgroupoids, and we give conditions under which the closure of a subgroupoid is again a subgroupoid.     

Multi-peakon solutions to a four-component Camassa-Holm type system

A four-component Camassa-Holm type system with cubic nonlinearity is investigated. It allows an arbitrary function $\Gamma(x,t)$ to be involved in to include some existing integrable peakon equations as special reductions. We obtain $N$-peakon solutions of the four-component Camassa-Holm type system with two special cases of $\Gamma(x,t)$. In particular, we give one- and two-peakon solutions in an explicit formula and are graphically plotted. Further, some interesting peaked solutions are found: some peakon waves possessing positive and negative amplitudes while others decaying and growing amplitudes.     

Analysis of complete integrability of a system inverse to the nonlinear Benney-Kaup system

We study a system inverse to the nonlinear dynamical Benney-Kaup system. For this system, we prove the existence of an infinite hierarchy of functionally independent and involution conservation laws; a pair of implicative and Noetherian operators is constructed which enables one to write the system in a bi-Hamiltonian form; we also present the explicit form of the Lax operator.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 45 No. 3, pp. 353–360, March, 1993.     

On integrability of power series

This paper deals with the integrability of a power series. Our results generalize certain results of Ram, and Askey and Karlin.     

The finite-dimensional super integrable system of a super NLS-mKdV equation

Based on the constructed Lie superalgebra, the super Hamiltonian structure of a NLS-mKdV hierarchy is obtained by making use of super-trace identity. Moreover, an explicit super Bargmann symmetry constraint and its associated binary nonlinearization of Lax pairs are carried out for the super NLS-mKdV system.     

On the integrability of radial basis functions

In this paper we investigate the integrability of certain radial basis functions. From the following forms of function σ, $$\varphi \left( r \right) = \left\{ \begin{gathered} \sum\limits_{k = 0}^{d + [a]} {c_k r^{a - k} + g(r) } r > A, \hfill \\ \sum\limits_{k = 0}^{d + [a]} {c_k r^{a - k} \ln r + g(r), } r > A. \hfill \\ \end{gathered} \right.$$ where A≧0 and $g \circ || \circ || \in L^1 \left( {R^d } \right)$ , we construct the function $$\psi (t) = \sum\limits_{j \in J} {a_j \varphi \left( {||t - t_j ||} \right),} $$ where J is a finite index set, $\left\{ {a_j } \right\}_{j \in J} \subseteq R$ and $\left\{ {t_j } \right\}_{j \in J} \subseteq R^d $ . We show that if $\hat \psi $ is continuous at the origin, the ψ is integrable in R^d.     

On integrability in the LIL for degenerateU-statistics

It is shown by example that square integrability of the kennelh of a completely degenerateU-statistic is not a necessary condition for the law of the iterated logarithm to hold. Necessary integrability conditions are given onh which are in a sense the strongest possible. Sufficient conditions for a degenerateU-statistic of order 2 to satisfy the LIL, weaker than square integrability of the kernel, are also given.Research partially supported by NSF Grant No. DMS-93-00725. Part of this author's work was done at the University of Bielefeld, supported by the Deutsche Forschungsgemeinshaft, Sonderforschungbereich 343, Diskrete Structuren in der Mathematik.Research partially supported by the Army Research Office and the National Security Agency.     

On algebraic integrability of Gelfand-Zeitlin fields

We generalize a result of Kostant and Wallach concerning the algebraic integrability of the Gelfand-Zeitlin vector fields to the full set of strongly regular elements in \mathfrakg\mathfrakl \mathfrak{g}\mathfrak{l} (n, ℂ). We use decomposition classes to stratify the strongly regular set by subvarieties X_D {X_\mathcal{D}} . We construct an étale cover [^(\mathfrakg)]_D {\hat{\mathfrak{g}}}_\mathcal{D} of X_D {X_\mathcal{D}} and show that X_D {X_\mathcal{D}} and [^(\mathfrakg)]_D {\hat{\mathfrak{g}}}_\mathcal{D} are smooth and irreducible. We then use Poisson geometry to lift the Gelfand-Zeitlin vector fields on X_D {X_\mathcal{D}} to Hamiltonian vector fields on [^(\mathfrakg)]_D {\hat{\mathfrak{g}}}_\mathcal{D} and integrate these vector fields to an action of a connected, commutative algebraic group.