一类孤子方程族及其多个Hamilton结构

本文建立了一个含11个位势的新的等谱问题,得到了一组新的Lax对,由此得到一类新的孤子方程族.该族是Liouville可积的,具有4-Hamilton结构,且循环算子的共轭算子是一个遗传对称算子.另外,为确切说明所得方程族是一个4-Hamilton结构,在附录中证明了所得的4个Hamilton算子的线性组合恒为Hamilton算子.     

A recursive methodology for the solution of semi-analytical rectangular anisotropic thin plates in linear bending

A new recursive methodology is introduced to solve anisotropic thin plates bending problems, which is based on three concepts: (a) the plate differential operator additively decomposed obeying a material constitutive hierarchy; (b) the plate displacement field expanded into an infinite series and (c) an homotopy-like scheme applied to determine each term of the series. The pb-2 Rayleigh–Ritz Method is adopted to construct the solution space. Convergence conditions are presented and related to the differential operator decomposition and material’s anisotropy degree. Different cases of geometry, loading and boundary conditions were studied using the methodology and excellent agreement with available solutions was found.     

Explicit Green operators for quantum mechanical Hamiltonians. I. The hydrogen atom

We study a new approach to determine the asymptotic behaviour of quantum many-particle systems near coalescence points of particles which interact via singular Coulomb potentials. This problem is of fundamental interest in electronic structure theory in order to establish accurate and efficient models for numerical simulations. Within our approach, coalescence points of particles are treated as embedded geometric singularities in the configuration space of electrons. Based on a general singular pseudo-differential calculus, we provide a recursive scheme for the calculation of the parametrix and corresponding Green operator of a nonrelativistic Hamiltonian. In our singular calculus, the Green operator encodes all the asymptotic information of the eigenfunctions. Explicit calculations and an asymptotic representation for the Green operator of the hydrogen atom and isoelectronic ions are presented.     

Locality of Symmetries Generated by Nonhereditary, Inhomogeneous, and Time-Dependent Recursion Operators: A New Application for Formal Symmetries

Using the methods of the theory of formal symmetries, we obtain new easily verifiable sufficient conditions for a recursion operator to produce a hierarchy of local generalized symmetries. An important advantage of our approach is that under certain mild assumptions it allows to bypass the cumbersome check of hereditariness of the recursion operator in question, what is particularly useful for the study of symmetries of newly discovered integrable systems. What is more, unlike the earlier work, the homogeneity of recursion operators and symmetries under a scaling is not assumed as well. An example of nonhereditary recursion operator generating a hierarchy of local symmetries is presented.     

Complexity Analysis via Approach Spaces

Complexity of a recursive algorithm typically is related to the solution to a recurrence equation based on its recursive structure. For a broad class of recursive algorithms we model their complexity in what we call the complexity approach space, the space of all functions in X?=? ]0,?∞?] ^Y , where Y can be a more dimensional input space. The set X, which is a dcpo for the pointwise order, moreover carries the complexity approach structure. There is an associated selfmap Φ on the complexity approach space X such that the problem of solving the recurrence equation is reduced to finding a fixed point for Φ. We will prove a general fixed point theorem that relies on the presence of the limit operator of the complexity approach space X and on a given well founded relation on Y. Our fixed point theorem deals with monotone selfmaps Φ that need not be contractive. We formulate conditions describing a class of recursive algorithms that can be treated in this way.     

The FE-closure operator in countable-valued logic

The FE-closure operator on set P _N of functions of countable-valued logic is considered. It is proved that any general recursive operator (defined in the Herbrand-Gödel formalism) can be realized in the language of FE-closure. It is established that the class of relations definable in the language of FE-closure coincides with class Σ ₁ ¹ in the Kleene analytic hierarchy. It is shown that the membership in an FE-closed class of any nontrivial homogeneous function implies that the entire set of homogeneous functions is contained in this class.     

Recursion relations for the constrained multi-component KP hierarchy

In this paper, we define a new constrained multi-component KP(cMKP) hierarchy which contains the constrained KP(cKP) hierarchy as a special case. We derive the recursion operator of the constrained multi-component KP hierarchy. As a special example, we also give the recursion operator of the constrained two-component KP hierarchy.     

On the Lie algebra structures connected with Hamiltonian dynamical systems

We construct the hierarchies of master symmetries constituting Virasoro-type algebras for the Hamiltonian vector fields preserving a recursion operator. Similarly, repeatedly contracting a Hamiltonian vector field with the corresponding recursion operator, we define an Abelian Lie algebra of the thus obtained hierarchy of vector fields. The approach is shown to be applicable for the Volterra and Toda lattices. Published in Ukrainskii Matematicheskii Zhurnal, Vol. 49, No. 5, pp. 699–705, May, 1997.     

On Nondeterminism,Enumeration Reducibility and Polynomial Bounds

Enumeration reducibility is a notion of relative computability between sets of natural numbers where only positive information about the sets is used or produced. Extending e-reducibility to partial functions characterises relative computability between partial functions. We define a polynomial time enumeration reducibility that retains the character of enumeration reducibility and show that it is equivalent to conjunctive non-deterministic polynomial time reducibility. We define the polynomial time e-degrees as the equivalence classes under this reducibility and investigate their structure on the recursive sets, showing in particular that the pe-degrees of the computable sets are dense and do not form a lattice, but that minimal pairs exist. We define a jump operator and use it to produce a characterisation of the polynomial hierarchy.     

THE RECURSION OPERATOR FOR A CONSTRAINED CKP HIERARCHY

This paper gives a recursion operator for a 1-constrained CKP hierarchy, and by the recursion operator it proves that the 1-constrained CKP hierarchy can be reduced to the mKdV hierarchy under condition q = r.     

Closing the gap between the continuous functionals and recursion in ^3E

We show that the length of a hierarchy of domains with totality, based on the standard domain for the natural numbers and closed under dependent products of continuously parameterised families of domains will be the first ordinal not recursive in and any real. As a part of the proof we show that the domains of the hierarchy share important properties with the types of continuous functionals. The main result can also be viewed as a representation theorem for recursion in . Received: August 1, 1994     

Symmetries for the Ablowitz–Ladik Hierarchy: Part II. Integrable Discrete Nonlinear Schrödinger Equations and Discrete AKNS Hierarchy

In the paper, we continue to consider symmetries related to the Ablowitz–Ladik hierarchy. We derive symmetries for the integrable discrete nonlinear Schrödinger hierarchy and discrete AKNS hierarchy. The integrable discrete nonlinear Schrödinger hierarchy is in scalar form and its two sets of symmetries are shown to form a Lie algebra. We also present discrete AKNS isospectral flows, non‐isospectral flows and their recursion operator. In continuous limit these flows go to the continuous AKNS flows and the recursion operator goes to the square of the AKNS recursion operator. These discrete AKNS flows form a Lie algebra that plays a key role in constructing symmetries and their algebraic structures for both the integrable discrete nonlinear Schrödinger hierarchy and discrete AKNS hierarchy. Structures of the obtained algebras are different structures from those in continuous cases which usually are centerless Kac–Moody–Virasoro type. These algebra deformations are explained through continuous limit and degree in terms of lattice spacing parameter h.     

Evaluating the Complexity of Index Sets for Families of General Recursive Functions in the Arithmetic Hierarchy

The complexity of index sets of families of general recursive functions is evaluated in the Kleene–Mostowski arithmetic hierarchy.     

An algorithm for solving the eigenvalue problem for a class of operator pencils

We study the generalized eigenvalue problem for a uniformly hyperbolic or totally hyperbolic polynomial operator pencil of arbitrary order. In the context of the variational approach to the problem of determining the eigenvalues of such pencils we propose and justify a recursive algorithm for finding an eigenpair. To accelerate the convergence we propose using the Rayleigh-Ritz procedure. We give data from a numerical implementation of the algorithm. Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, No. 37, 1994, pp. 24–28.     

New hierarchy of integrable system bi-Hamiltonian structure and constrained flows

We have considered the hierarchy of integrable systems associated with the unstable nonlinear Schrodinger equation. The spectral gradient approach and the trace identity are used to derive the bi-Hamiltonian structure of the system. The bi-Hamiltonian property and the square eigenfunctions determined via the spectral gradient approach are then used to construct constrained flows, which is also proved to be derivable from a rational Lax operator. This new Lax operator of the constrained flows is seen to generate the classical r-matrix. Lastly it is also explicitly demonstrated that the different integrals of motion of the constrained flows Poisson commute.     

BKP 与CKP 可积系列的递归算子

借助于新引进的算子B, 本文给出了BKP 与CKP 可积系列约束条件在其Lax 算子L中的动力学变量上的具体体现, 即奇数阶动力学变量u_2k+1 能被偶数阶动力学变量u_2k 显式表达. 同时本文给出了BKP 与CKP 可积系列的流方程以及(2n + 1)- 约化下递归算子的统一公式, 揭示了BKP 可积系列和CKP 可积系列的重要区别. 作为例子, 本文给出了BKP 与CKP 可积系列在3- 约化下的递归算子的显式表示, 并验证了u₂ 的t₁ 流通过递归算子的确可以产生u₂ 的t₇ 流, 该流方程与3- 约化下产生的对应流方程是一致的.     

Complexity of winning strategies

Rabin has given an example of a game with recursive rules but no recursive winning strategy. We show that such a game always has a hyperarithmetical winning strategy, but arbitrarily high levels of the hyperarithmetical hierarchy may be needed. We also exhibit a recursively enumerable game which has no hyperarithmetical winning strategy.     

非等谱Lax算子族的Virasoro代数

非等谱Ｌａｘ算子族的Ｖｉｒａｓｏｒｏ代数马文秀（复旦大学数学研究所，上海２００４３３）国家博士后科学基金资助项目．１９９１年７月２５日收到．１９９２年７月６日收到修改稿．一、引言Ｌａｘ算子方法［１］在可积系统理论中有着广泛的应用．从一个谱问题出发我们...     

Integrable coupling of the Ablowitz–Ladik hierarchy and its Hamiltonian structure

The trace identity is generalized to work for the discrete zero-curvature equation associated with the Lie algebra possessing degenerate Killing forms. Then a kind of integrable coupling of the Ablowitz–Ladik (AL) hierarchy is obtained and its Hamiltonian structure is worked out. Moreover, Liouville integrability of the integrable coupling is demonstrated.     

Symmetric q-Deformed KP Hierarchy

Based on the analytic property of the symmetric q-exponent e_q(x),a new symmetric q-deformed Kadomtsev-Petviashvili(q-KP for short) hierarchy associated with the symmetric q-derivative operator α_q is constructed.Furthermore,the symmetric q-CKP hierarchy and symmetric q-BKP hierarchy are defined.The authors also investigate the additional symmetries of the symmetric q-KP hierarchy.