高维空间中连接双曲鞍点的异宿环的稳定性

本文考虑任意有限维空间连接两个双曲鞍点的非扭曲异宿环的稳定性问题.在可定义Poincar′e映射的条件下,给出了异宿环在其部分邻域内是渐近稳定的判据,将3维系统鞍点异宿环的稳定性结果推广到了m+n+2维空间中的非扭曲的2-鞍点异宿环,其中m 0,n 0.通过在两个鞍点充分小邻域内,给出系统在适当的线性变换下的第一个规范型,接着采用将局部稳定流形和不稳定流形拉直的变换建立了第二个规范型.然后,在鞍点P1,P2的小邻域内适当选取两个异宿轨道的横截面,并分别分两部分来构造流映射.在鞍点P1,P2的小邻域内,本质上我们利用线性近似系统的流来构造奇异流映射的主部,而在鞍点的邻域外的异宿轨道的小管状邻域内,则用近似于一个非奇异矩阵的微分同胚来获得正则流映射.将四者复合即得到定义于P1小邻域内某横截面上的Poincar′e映射.最后,我们通过技巧性地估计向量的模,给出了在横截面上Poincar′e映射的初始点与首次回归点离异宿轨道与横截面交点的距离之比,由此得到关于非扭曲2-点异宿环的非常简洁的稳定性判据.     

一类3维反转系统中的异维环分支

研究了一类3维反转系统中包含2个鞍点的对称异维环分支问题, 且仅限于研究系统的线性对合R的不变集维数为1的情形. 给出了R-对称异宿环与R-对称周期轨线存在和共存的条件, 同时也得到了R-对称的重周期轨线存在性. 其 次, 给出了异宿环、 同宿轨线、 重同宿轨线和单参数族周期轨线的存在性、 唯一性和共存性等结论, 并且发现不可数无穷条周期轨线聚集在某一同宿轨线的小邻域内. 最后给出了相应的分支图.     

一类异宿环分支极限环的唯一性

本文研究平面上一类两点或三点异宿环附近极限环的分支,在一简洁条件下证明了异宿环分支极限环的唯一性,并给出了极限环唯一存在的充要条件.作为对三维余维2分支的应用,解决了所出现的两点异宿环产生唯一极限环的问题.     

两点粗异宿环分支

研究了情形的两点粗异宿环的分支问题, 其中和为未扰系统在鞍点pi ( i= 1, 2)处的一对主特征值. 在非扭曲和横截性条件下获得了1条1-周期轨道, 1条1-周期轨道和1条1-同宿环, 2条1-周期轨道以及1条两重 1-周期轨道的存在性. 同时, 还得到了相应的分支曲面和存在域, 给出了相应的分支图.     

连接两个具有一维不稳定流形的双曲鞍点异宿环的稳定性

本文研究任意有限维空间中连接两个具有一维不稳定流形的双曲鞍点异宿环的稳定性.借助适当的线性变换和坐标变换,将局部稳定流形和不稳定流形拉直,利用奇异流映射和正则流映射构造了Poincaré映射.通过技巧性地估计向量的模,给出了在横截面上Poincaré映射的初始点与首次回归点离异宿轨道与横截面交点的距离之比,得到了高维空间中连接两个带有一维不稳定流形的异宿环的非常简洁的稳定性判据.     

一类余维3的鞍-焦点异宿环分支

对余维3系统Xμ(x)具有包含一个双曲鞍-焦点O1和一个非双曲鞍-焦点O2的异宿环￡进行了研究.证明了在￡的邻域内有可数无穷条周期轨线和异宿轨线,当非粗糙异宿轨线ΓO破裂时Xμ(x)会产生同宿轨分支,并给出了相应的分支曲线和两种同宿环共存的参数值.在3参数扰动下ΓO破裂和O2点产生Hopf分支的情况下,在￡的邻域内有一条含O1点同宿环,可数无数多条的轨线同宿于O2点分支出的闭轨HO,一条或无穷多条(可数或连续统的)异宿轨线等.     

一类余维3的鞍-焦点异宿环分支

对余维3系统X_μ(x)具有包含一个双曲鞍-焦点O_1和一个非双曲鞍-焦点O_2的异宿环f进行了研究.证明了在f的邻域内有可数无穷条周期轨线和异宿轨线,当非粗糙异宿轨线Γ~0破裂时X_μ(x)会产生同宿轨分支,并给出了相应的分支曲线和两种同宿环共存的参数值.在3参数扰动下Γ~0破裂和O_2点产生Hopf分支的情况下,在f的邻域内有一条含O_1点同宿环,可数无效多条的轨线同宿于O_2点分支出的闭轨H_0,一条或无穷多条(可数或连续统的)异宿轨线等.     

同宿、异宿环分支出极限环的唯一性

本文在一简洁条件下证明任一含细鞍点的孤立同宿环及对称的双同宿环和两点异宿环至多产生一个极限环。     

非扭曲异宿环分支

考虑高维系统非扭曲细异宿环分支,给出了1-同宿轨道和1-周期轨道的存在性和存在域,并得到了2-重周期轨道的分支曲面.最后,这些分支结果被应用于平面系统细异宿环,获得了新的有趣的结论.     

三维反转系统中余维2和3的异维环分支

研究了三维反转系统中具有2个鞍点的对称异维环分支问题.在此反转性意味着存在线性对合R,使得系统在R变换和时间逆向条件下仍保持不变.当R的不动点构成集合的维数dim Fix(R)=1时,我们研究了R-对称异维环,R-对称周期轨线,同宿环,重周期轨线和具有单参数族的无穷条周期轨线的存在性及它们的共存性.本文也明确得到了对称异维环的重同宿分支,且分支出的不可数无穷条周期轨道聚集在某条同宿轨道的小邻域内.进一步,作者也证明了相应的分支曲面及其存在区域.对于dim Fix(R)=2时的情形,本文得到了系统可分支出R-周期轨道和R-对称异宿环.     

Bifurcations of Rough Heteroclinic Loops with Three Saddle Points

In this paper, we study the bifurcation problems of rough heteroclinic loops connecting three saddle points for a higher-dimensional system. Under some transversal conditions and the nontwisted condition, the existence, uniqueness, and incoexistence of the 1-heteroclinic loop with three or two saddle points, 1-homoclinic orbit and 1-periodic orbit near Γ are obtained. Meanwhile, the bifurcation surfaces and existence regions are also given. Moreover, the above bifurcation results are extended to the case for heteroclinic loop with l saddle points. Received January 4, 2001, Accepted July 3, 2001.     

Bifurcation of limit cycles from a heteroclinic loop with a cusp

In this article, we study the expansion of the first Melnikov function of a near-Hamiltonian system near a heteroclinic loop with a cusp and a saddle or two cusps, obtaining formulas to compute the first coefficients of the expansion. Then we use the results to study the problem of limit cycle bifurcation for two polynomial systems.     

Degenerate bifurcations of nontwisted heterodimensional cycles with codimension 3

Bifurcations of heterodimensional cycles with highly degenerate conditions are studied by establishing a suitable local coordinate system in three-dimensional vector fields. The existence, coexistence and noncoexistence of the periodic orbit, homoclinic loop, heteroclinic loop and double periodic orbit are obtained under some generic hypotheses. The bifurcation surfaces and the existence regions are located; the number of the bifurcation surfaces exhibits variety and complexity of the bifurcation of degenerate heterodimensional cycles. The corresponding bifurcation graph is also drawn.     

BIFURCATIONS OF ROUGH 3—POINT—LOOP WITH HIGHER DIMENSIONS

The authors study the bifurcation problems of rough heteroclinic loop connecting three saddle points for the case β1 > 1, β2 > 1, β3 < 1 and β1β2β3 < 1. The existence, number, coexistence and incoexistence of 2-point-loop, 1-homoclinic orbit and 1-periodic orbit are studied. Meanwhile, the bifurcation surfaces and existence regions are given.     

On the Bifurcations of a Hamiltonian Having Three Homoclinic Loops under Z3 Invariant Quintic Perturbations

A cubic system having three homoclinic loops perturbed by Z3 invariant quintic polynomials is considered. By applying the qualitative method of differential equations and the numeric computing method, the Hopf bifurcation, homoclinic loop bifurcation and heteroclinic loop bifurcation of the above perturbed system are studied. It is found that the above system has at least 12 limit cycles and the distributions of limit cycles are also given.     

Codimension 3 Non-resonant Bifurcations of Rough Heteroclinic Loops with One Orbit Flip

Heteroclinic bifurcations in four dimensional vector fields are investigated by setting up a local coordinates near a rough heteroclinic loop. This heteroclinic loop has a principal heteroclinic orbit and a non-principal heteroclinic orbit that takes orbit flip. The existence, nonexistence, coexistence and uniqueness of the 1-heteroclinic loop, 1-homoclinic orbit and 1-periodic orbit are studied. The existence of the two-fold or three-fold 1-periodic orbit is also obtained.     

A scenario for torus T destruction via a global bifurcation

We show a scenario of a two-frequency torus breakdown, in which a global bifurcation occurs due to the collision of a quasi-periodic torus T² with saddle points, creating a heteroclinic saddle connection. We analyze the geometry of this torus-saddle collision by showing the local dynamics and the invariant manifolds (global dynamics) of the saddle points. Moreover, we present detailed evidences of a heteroclinic saddle-focus orbit responsible for the type-II intermittency induced by this global bifurcation. We also characterize this transition to chaos by measuring the Lyapunov exponents and the scaling laws.     

Bifurcations of nontwisted heteroclinic loop

Bifurcations of nontwisted and fine heteroclinic loops are studied for higher dimensional systems. The existence and its associated existing regions are given for the 1-hom orbit and the 1-per orbit, respectively, and bifurcation surfaces of the two-fold periodic orbit are also obtained. At last, these bifurcation results are applied to the fine heteroclinic loop for the planar system, which leads to some new and interesting results.