2n阶两点边值问题的多重非平凡解

本文主要研究2n阶两点边值问题的多重非平凡解的存在性．利用不动点指数理论和Leray-schauder度,在一般的非线性条件下,证明了2n阶两点边值问题至少有六个非平凡解的存在性．而且,如果非线性项是奇函数,则至少有八个非平凡解的存在．     

带有奇异项的临界增长p-Laplace方程的非平凡解

本文研究了一种带有奇异项的临界增长p-Laplace方程在N维空间中的有界集上非平凡解的问题,利用山路引理和集中紧性原理,得出方程在非线性项满足一定条件下有非平凡解的结果.     

Pohozaev恒等式及其在非线性椭圆型方程中的应用

在非线性椭圆型偏微分方程的研究中,Pohozaev恒等式在研究非平凡解的存在性和非存在性时起着十分重要的作用.本文旨在介绍Pohozaev恒等式及其在非线性椭圆型问题研究中的应用.首先介绍有界区域和无界区域上几种典型的Pohozaev恒等式,并得到几类非线性椭圆型方程存在解的必要条件,进而得到对应的方程非平凡解的非存在性和存在性结果.其次将介绍非线性椭圆型方程的局部Pohozaev恒等式,由此证明非线性椭圆型微分方程近似解序列的紧性,并得到几类典型非线性椭圆型方程的无穷多解存在性.最后利用非线性椭圆型方程的局部Pohozaev恒等式来研究其波峰解,得到波峰解的局部唯一性,并由此判断波峰解的对称性等特征.     

几类非线性差分方程的对称和精确解

本文将微分方程的Lie变换群方法推广到差分方程,给出了三类非线性差分方程的不变变换,利用这种变换由差分方程的平凡解得到非平凡的单参数解族。     

RN中含Φ-Laplace算子和凹凸非线性项的拟线性椭圆型方程解的存在性

该文研究了全空间中一类含Φ-Laplace算子和凹凸非线性项的拟线性椭圆型方程非平凡解的存在性和多重性.利用Nehari流形方法和纤维映射等技巧,在参数较小的情况下,得到方程至少有两个非平凡解,其中一个是基态解.     

带有非线性边界条件的非齐次拟线性椭圆型方程组的多解性

主要研究一组带有非线性边界条件的非齐次拟线性椭圆型方程组非平凡解的存在性和多解性.利用山路引理和Ekeland变分准则,得到当λ属于特定区间时,此方程组至少存在两个非平凡解.     

非线性非自治系统的等度渐近稳定性

研究了非线性非自治系统平凡解的等度渐近稳定性。利用一个或两个Lyapunov函数得到了保证所给系统的平凡解等度渐近稳定性的几个充分判据,最后给出两个例子说明本文结果.     

超线性Sturm-Liouville问题的非平凡解

本文通过对超线性 Sturm-Liouville 两点边值问题进行解的先验估计,讨论其非平凡解的存在性.我们不假定非线性项非负,也不只限于考虑正解,这是与已有讨论超线性方程解的先验估计的文献不同的.我们的关于非平凡解的存在性的结果,有些改进了已有结论,有些是新的.     

一个带Hardy项的椭圆方程的多重解

通过对偶变分方法证明了一个带Hardy项和临界非线性的非线性椭圆方程的非平凡解的存在性和多重性.     

一类含多奇性项的Grushin型算子方程解的渐近性质

本文研究了一类含多个奇性项的Grushin型算子方程非平凡解的渐近性质问题.当方程的非线性项满足临界指数增长条件时,利用Moser迭代方法和分析技巧,获得了方程的非平凡解在奇点处的渐近性质,推广了Laplace算子的相关结果.     

Infinite dimensional local linking and some applications to the Hamiltonian systems

In this paper we get an existence theorem of nontrivial critical points by using the local linking idea. As applications, we study the existence of nontrivial periodic solution of Hamiltonian systems.     

Special biconformal changes of K?hler surface metrics

The term “special biconformal change” refers, basically, to the situation where a given nontrivial real-holomorphic vector field on a complex manifold is a gradient relative to two K?hler metrics, and, simultaneously, an eigenvector of one of the metrics treated, with the aid of the other, as an endomorphism of the tangent bundle. A special biconformal change is called nontrivial if the two metrics are not each other’s constant multiples. For instance, according to a 1995 result of LeBrun, a nontrivial special biconformal change exists for the conformally-Einstein K?hler metric on the two-point blow-up of the complex projective plane, recently discovered by Chen, LeBrun and Weber; the real-holomorphic vector field involved is the gradient of its scalar curvature. The present paper establishes the existence of nontrivial special biconformal changes for some canonical metrics on Del Pezzo surfaces, viz. K?hler–Einstein metrics (when a nontrivial holomorphic vector field exists), non-Einstein K?hler–Ricci solitons, and K?hler metrics admitting nonconstant Killing potentials with geodesic gradients.     

Bifurcation effects in thermodynamics of Markovian copolymers away from the critical point

Numerical computations of inhomogeneous free-energy extremals on the basis of the thermodynamic model of Markovian copolymers have shown that they exhibit two qualitatively different scenarios of behavior with varying temperature. The first occurs in systems with close points of the trivial and nontrivial spinodals, while the second scenario takes place when the turning point of an extremal is sufficiently far away from the point of the nontrivial spinodal. In this case, as the binodal is approached, the model exhibits a secondary bifurcation point, i.e., the intersection point with the homogeneous nontrivial extremal issuing from the point of the trivial spinodal. At this point, the homogeneous nontrivial extremal becomes unstable with respect to periodic perturbations of frequency q* corresponding to a bifurcation of inhomogeneous extremals from the trivial state (point of the nontrivial spinodal). This bifurcation is studied for lamellar, hexagonal, and body-centered cubic structures. The evolution of the extremals is numerically computed until an absolutely stable state corresponding to the binodal is reached.     

Homoclinic orbits for second order nonlinear <Emphasis Type="Italic">p</Emphasis>-Laplacian difference equations

The paper proves the existence of nontrivial homoclinic orbits for second order nonlinear p-Laplacian difference equations without assumptions on periodicity using the critical point theory. Moreover, if the nonlinearity is an odd function, the existence of an unbounded sequence of nontrivial homoclinic orbits is proved.     

Multibump solutions for discrete periodic nonlinear Schrödinger equations

In this paper, we study the existence of multibump solutions for discrete nonlinear Schrödinger equations with periodic potentials. We first reduce the existence of multibump homoclinic solutions to the existence of an isolated homoclinic solution with a nontrivial critical group. Then, we study the existence of homoclinics with nontrivial critical groups for both superlinear and asymptotically linear discrete periodic nonlinear Schrödinger equations, and we provide simple sufficient conditions for the existence of homoclinics with nontrivial critical groups in the positive definite case. As an application, we get, without any symmetry assumptions, infinitely many geometrically distinct homoclinic solutions with exponential decay at infinity.     

Irreducible weight modules over the twisted Schrödinger-Virasoro algebra

It is shown that the support of an irreducible weight module over the SchrSdinger-Virasoro Lie algebra with an infinite-dimensional weight space coincides with the weight lattice, and all nontrivial weight spaces of such a module are infinite-dimensional. As a by-product, it is obtained that every simple weight module over Lie algebra of this type with a nontrivial finite-dimensional weight space is a Harish-Chandra module.     

Homoclinic Orbits of Nonlinear Functional Difference Equations

In this paper, by using the critical point theory, we obtain the existence of a nontrivial homoclinic orbit which decays exponentially at infinity for nonlinear difference equations containing both advance and retardation without any periodic assumptions. Moreover, if the nonlinearity is an odd function, the existence of an unbounded sequence of nontrivial homoclinic orbits which decay exponentially at infinity is obtained.      

On the stability of a domain-wall brane model

We establish stability and nonstability results for a domain-wall brane model arising in classical field theory. In particular, we show the nonexistence of nontrivial bounded solutions on the real line for a coupled pair of parameter dependent linear second order ordinary differential equations for an open set of those parameters. Moreover, we establish the existence of nontrivial solutions for a hypersurface of the parameters. We use Fredholm theory for compact linear operators combined with the Lyapunov-Schmidt method to prove our results. The model is stable, respectively unstable, for those parameters for which the coupled system does not, respectively does, have nontrivial solutions.     

Existence of multiple and sign-changing solutions for a second-order nonlinear functional difference equation with periodic coefficients

In the present paper, we apply the method of invariant sets of descending flow to establish a series of criteria to ensure that a second-order nonlinear functional difference equation with periodic boundary conditions possesses at least one trivial solution and three nontrivial solutions. These nontrivial solutions consist of sign-changing solutions, positive solutions and negative solutions. Moreover, as an application of our theoretical results, an example is elaborated. Our results generalize and improve some existing ones.     

Union and tangle

Shibuya proved that any union of two nontrivial knots without local knots is a prime knot. In this note, we prove it in a general setting. As an application, for any nontrivial knot, we give a knot diagram such that a single unknotting operation on the diagram cannot yield a diagram of a trivial knot.