新(2+1)-维超可积系统的生成

本文利用二项式残数表示方法生成(2+1)-维超可积系统. 由这些系统得到了一个新的(2+1)-维超孤子族,它能约化为(2+1)-维超非线性Schrodinger方程. 特别地,我们得到两个具有重要物理应用的结果,一个是(2+1)-维超可积耦合方程,另一个是(2+1)-维的扩散方程. 最后借助超迹恒等式给出了新(2+1)-维超可积系统的Hamilton结构.     

(3+1)维短波方程的不变子空间和精确解

利用不变子空间方法研究了(3+1)维短波方程的不变子空间和精确解.在(2+1)维短波方程增加一维的情形下,构造了更加广泛的精确解,同时也得到了超曲面的爆破解.主要结果不仅推广了不变子空间理论在高维非线性偏微分方程中的应用,而且对研究高维方程的动力系统有重要意义.     

两类(2+1)维可积系统

利用一个广义等谱问题的相容性得到了一个广义零曲率方程.作为其应用,首先利用loop代数设计了两个广义等谱问题,然后利用零曲率方程导出了两类(2+1)维Lax可积系统.     

高维可积模型探索

从3个不同方面对可能存在的高维可积模型作了研究.(1)从(1+1)维可积模型的强对称算子出发,可以构造一类(n+1)维的可积模型:高维破裂孤子方程;(2)对于广义Virasoro代数的每一个具体实现,可以得到大量的在具有广义Virasoro对称代数意义下的高维可积模型;(3)从具有共形不变性的Schwartz型的方程出发,可以得到许多具有Painlevé性质意义下的可积模型.     

两个具有相同Hirota双线性方程的(3+1)-维演化方程的拟周期波解

应用Hirota双线性方法,构造了一个用Riemannθ函数表示的双线性方程的拟周期波解.应用到两个(3+1)-维演化方程:一个是与AKNS可积方程族相关的可积模型,另一个是著名的Jimbo-Miwa方程,分别得到了这两个演化方程的拟周期波解.     

(2+1)维modified Zakharov-Kuznetsov方程的复合型新解

给出函数变换,变量分离形式解与第一种椭圆方程相结合的方法,构造了(2+1)维modified Zakharov-Kuznetsov(m ZK)方程的多种复合型新解.步骤一,给出两种函数变换,将(2+1)维m ZK方程转化为能够获得变量分离解的非线性发展方程.步骤二,给出非线性发展方程的变量分离形式解,通过第一种椭圆方程及其相关结论,构造了(2+1)维m ZK方程的双孤子解和双周期解等复合型新解.     

(2+1)维Broer-Kaup-Kupershmidt方程组的行波解

借助于计算机代数系统Mathematica,利用推广的简单方程方法构造了(2+1)维Broer-Kaup-Kupershmidt方程组的新的精确行波解,分别以含有双参数的用双曲函数,三角函数和有理函数表示,其中双曲函数表.示的行波解中参数取特殊值时可得到文献已有的孤波解.方法也适用于其它非线性发展方程(组).     

Riccati方程与(2+1)维非线性物理模型的分离变量解

对于(2+1)维非线性物理模型,欲获其解并非易事.本文试图在变量分离法中,通过设定的R iccati方程来得到方程的解.同时,以(2+1)维Bo iti-L eon-M anna-P em p inelli方程和Burgers方程为例来说明之.     

(1+1)维Burgers方程新的行波解

通过采用新的exp(-ρ(ξ))展式法,得到了(1+1)维Burgers方程形如u(ξ)=αm(exp(-ρ(ξ)))m+αm-1(exp(-ρ(ξ)))m-1+…的新行波解.该方法也可以应用于求解其它许多的非线性演化方程.     

高阶(2+1)维Broer-Kaup方程的局域相干结构

利用推广的齐次平衡方法,研究高阶(2+1)维Broer-Kaup方程的局域相干结构.首先基于推广的齐次平衡方法,给出这个模型的一个非线性变换,并把它变换成一个线性化的方程.然后从线性化方程出发,构造出一个分离变量的拟解.由于拟解中不仅含有两个y的任意函数,而且还有{αi,βi,γk,kj,lk}和{N,M,L}这些参数可以任意选取,因此合适的选择这些函数和参数,可以得到新的相当丰富的孤子结构.方法直接而简单,可推广应用一大类(2+1)维非线性物理模.     

On the equationx(x +d 1)…(x + (k - 1)d 1) =y(y +d 2)…(y + (mk - 1)d 2)

For given positive integersm ≥ 2,d ₁ andd ₂, we consider the equation of the title in positive integersx, y andk ≥ 2. We show that the equation implies thatk is bounded. For a fixedk, we give conditions under which the equation implies that max(x, y) is bounded. Dedicated to the memory of Professor K G Ramanathan     

The cardinality of FM(1+1+n)

The aim of this note is to develop a counting formula for the modular lattice FM(1+1+n) freely generated by two single elements and an n-element chain. This answers Problem 44 in Birkhoff [1] which asks one to determine FM(1+1+n). The proof of our recursive formula is based on the scaffolding method developed by R. Wille.     

Über die Funktionalgleichungf (1 + x) + f (1 + f (x)) = 1

Ohne Zusammenfassung     

Zur graphischen Integration der linearen Differentialgleichung n. Ordnung (an D + 1) (an−1 D + 1) ..... (a1 D + 1) y = s (x)(a1 D + 1) y = s (x)

Ohne Zusammenfassung     

On the integrability of the (1+1)-dimensional and (2+1)-dimensional Ito equations

Under investigation in this paper are the (1+1)-dimensional and (2+1)-dimensional Ito equations. With the help of the Bell polynomials method, Hirota bilinear method and symbolic computation, the bilinear representations, N-soliton solutions, bilinear Bäcklund transformations and Lax pairs of these two equations are obtained, respectively. In particular, we obtain a new bilinear form and N-soliton solutions of the (2+1)-dimensional Ito equation. The bilinear Bäcklund transformation and Lax pair of the (2+1)-dimensional Ito equation are also obtained for the first time. Copyright © 2014 John Wiley & Sons, Ltd.     

U(n + 1) × U(p + 1)-Hermitian metrics on the manifold S 2n+1 × S 2p+1

A two-parameter family of invariant almost-complex structures J _α,c is given on the homogeneous space M × M’ = U(n + 1)/U(n) × U(p + 1)/U(p); all these structures are integrable. We consider all invariant Riemannian metrics on the homogeneous space M × M’. They depend on five parameters and are Hermitian with respect to some complex structure J _α,c . In this paper, we calculate the Ricci tensor, scalar curvature, and obtain estimates of the sectional curvature for any metric on M × M’. All the invariant metrics of nonnegative curvature are described. We obtain the extremal values of the scalar curvature functional on the four-parameter family of metrics g _{α,c,λ,λ’;1} .     

Nonholonomic (n + 1)-webs

We consider a nonholonomic (n + 1)-web NW on an n-dimensional manifold M, i.e., n + 1 codimension 1 distributions on M. We prove that a web NW on M is equivalent to a G-structure with structure group λE, the group of scalar matrices. We find the structure equations of a web NW and the integrability conditions of the distributions of a web NW. It is shown that on a manifold with nonholonomic (n + 1)-web an affine connection Γ arises naturally for which the distributions of the web are totally geodesic. We consider the case when the connection Γ has zero curvature and, in particular, when a web NW is defined by invariant distributions on a Lie group. In the case when all distributions of a web NW on a Lie group are integrable, we find the equations of this group in terms of local coordinates.     

One and two soliton solutions for the sinh–Gordon equation in (1+1), (2+1) and (3+1) dimensions

In this work we study the nonlinear sinh–Gordon equation in (1+1), (2+1) and (3+1) dimensions. We use the simplified form of Hirota’s method, to derive one and two soliton solutions for each equation.