多参数等变分歧问题关于左右等价的开折

基于奇点理论中光滑映射芽的左右等价关系,在等变分歧问题研究中,相应地引入一种新的等价关系,得到了以紧李群Г为对称群的等变分歧问题的单参数Г-开折是A(Г)-平凡的判定方法,给出了等变分歧问题的开折是A(Г)-通用开折的充要条件.     

等变分歧问题的无穷小稳定开拓

基于奇点理论中光滑函数芽的左右等价,本文讨论等变分歧问题开折的稳定性,刻画了有限型等变分歧问题的无穷小开折的稳定性,并指出这类分歧问题A(Γ)-通用开折必为无穷小稳定开折.     

含两组状态变量的等变分歧问题在左右等价群下的开折

基于奇点理论中光滑映射芽的左右等价关系, 讨论多参数等变分歧问题关于左右等价的开折．将这种等变分歧问题的状态变量分为两组,其中属于同一组的诸状态变量可以独立地变化,而属于另一组的诸状态变量在变化过程中依赖于前一组中的诸状态变量．应用光滑映射芽开折理论中的相关方法和技巧,得到了一个含两组状态变量的多参数等变分歧问题的开折是通用开折的充要条件．     

含两组状态变量且参数具有对称性的等变分歧问题及其开折的稳定性

基于奇点理论中光滑映射芽的接触等价关系,讨论含两组状态变量且分歧参数带有对称性的等变分歧问题及其开折的稳定性,得到了一些基本结果,并且用横截性条件刻划了等变分歧问题的稳定性．     

关于两状态变量的等变分歧问题的通用开折

本讨论在等价群Ｌ（Γ）的子群Ｌ作用下多参数等变分歧问题的通用开折,所得到的一个主要结果是等变通用开折定理,它可看作是献「１」中相应结果的继续深入。     

等变两参数分歧问题的开折

在ｕ－等价群作用的情形下对等变两参数分歧问题（其中参数均取向量值）的开折进行研究,得到一个分歧问题的某个开折是通用开折的充要条件,也给出了一个开折可由另一个开折导出的充要条件等结论．     

含两组状态变量等变分歧问题开折的唯一性和稳定性

基于奇点理论中光滑映射芽的接触等价,讨论多参数等变分歧问题关于接触等价的开折的唯一性和稳定性.将这种等变分歧问题的状态变量分为两组,其中一组的诸状态变量可以独立地变化,而属于另一组的诸状态变量在变化过程中依赖于前一组中的诸状态变量.得出了在接触等价下,满足一定条件的等变分歧问题的万有开折是唯一的,并且给出了一定条件下等变分歧问题开折稳定的一个充要条件.     

带有多个分歧参数的等变分歧问题的万有开折

对于含一个分歧参数的分歧问题,已有万有开折定理阻［１,２］．本文考虑带有多个分歧参数的等变分歧问题,并且允许它的状态空间与靶空间可以不同,给出了等变万有开折定理的更一般的形式,［１,２］中相关结果其特殊情形．     

关于两状态变量组的等变分歧问题的通用开折

本文讨论在等价群 D( Γ)的子群 D作用下多参数等变分歧问题的通用开折 ,所得到的一个主要结果是等变通用开折定理 ,它可看作是文献 [1 ]中相应结果的继续深入     

Γ-等变分歧问题的Γ-BD υ-可决定性和Γ-C0接触υ-可决定性

本文研究了分歧理论中Γ-等变分歧问题的Γ-BD有限决定性和Γ-C0接触有限决定性问题.利用奇点理论和李群理论中的某些方法,获得了Γ-BD有限决定性和Γ-C0接触有限决定性的一个判别准则,推广了P.B. Percell和孙伟志关于C0接触有限决定结果.     

光滑映射芽的开折的分级稳定性

光滑映射芽各种稳定性的讨论,一直是奇点理论的一个重要部分． Ｔｈｏｍ Ｒ．［１］在创立突变论时,提出了映射芽的,ｒ－开折的稳定性理论．Ｗａｓｓｅｒｍａｎｎ Ｇ．［２］将之发展为开折的（ｒ,ｓ）稳定理论．本文将他们的结论发展为（ｒ１,ｒ２,…,ｒｄ）稳定性,在任意的分级情况下,得到强稳定性、弱稳定性及无穷小稳定性的等价性,并得到了一些基本结果．     

Reprint of: Refold rigidity of convex polyhedra

We show that every convex polyhedron may be unfolded to one planar piece, and then refolded to a different convex polyhedron. If the unfolding is restricted to cut only edges of the polyhedron, we identify several polyhedra that are “edge-refold rigid” in the sense that each of their unfoldings may only fold back to the original. For example, each of the 43,380 edge unfoldings of a dodecahedron may only fold back to the dodecahedron, and we establish that 11 of the 13 Archimedean solids are also edge-refold rigid. We begin the exploration of which classes of polyhedra are and are not edge-refold rigid, demonstrating infinite rigid classes through perturbations, and identifying one infinite nonrigid class: tetrahedra.     

Refold rigidity of convex polyhedra

We show that every convex polyhedron may be unfolded to one planar piece, and then refolded to a different convex polyhedron. If the unfolding is restricted to cut only edges of the polyhedron, we identify several polyhedra that are “edge-refold rigid” in the sense that each of their unfoldings may only fold back to the original. For example, each of the 43,380 edge unfoldings of a dodecahedron may only fold back to the dodecahedron, and we establish that 11 of the 13 Archimedean solids are also edge-refold rigid. We begin the exploration of which classes of polyhedra are and are not edge-refold rigid, demonstrating infinite rigid classes through perturbations, and identifying one infinite nonrigid class: tetrahedra.     

Periodic reiterated homogenization for elliptic functions

In this paper, we study reiterated homogenization for equations of the form . We assume that a is a Carathéodory function and satisfies some monotonicity and growth conditions and its reiterated unfolding converges almost everywhere to a Carathéodory type function. Under these assumptions, we show that the sequence of solutions converges to the solution of a limit variational problem. In particular this contains the case , where a is periodic in the second and third arguments, and continuous in each argument.     

Unfolding of a Quadratic Integrable System with a Homoclinic Loop

In this paper, we make a complete study of the unfolding of a quadratic integrable system with a homoclinic loop. Making a Poincaré transformation and using some new techniques to estimate the number of zeros of Abelian integrals, we obtain the complete bifurcation diagram and all phase portraits of systems corresponding to different regions in the parameter space. In particular, we prove that two is the maximal number of limit cycles bifurcation from the system under quadratic non-conservative perturbations. Received July 16, 1999, Revised March 15, 2001, Accepted May 25, 2001     

Clasification of (4,1)-stable Unfoldings of Map Germs with Codimensions≤5

§１．ＲｅｓｕｌｔＣｏｎｓｉｄｅｒｉｎｇｔｈｅｃｏａｒｓｅｎｅｓｓｏｆｔｈｅｅｑｕｉｖａｌｅｎｃｅｒｅｌａｔｉｏｎｏｎｕｎｆｏｌｄｉｎｇｓｕｓｅｄｉｎＴｈｏｍ＇ｓｃｅｌｅｂｒａｔｅｄｌｉｓｔｏｆｓｅｖｅｎｅｌｅｍｅｎｔａｒｙｃａｔａｓｔｒｏｐｈｅｓＷ...     

Restrictions and unfolding of double Hopf bifurcation in functional differential equations

The normal form of a vector field generated by scalar delay-differential equations at nonresonant double Hopf bifurcation points is investigated. Using the methods developed by Faria and Magalhães (J. Differential Equations 122 (1995) 181) we show that (1) there exists linearly independent unfolding parameters of classes of delay-differential equations for a double Hopf point which generically map to linearly independent unfolding parameters of the normal form equations (ordinary differential equations), (2) there are generically no restrictions on the possible flows near a double Hopf point for both general and -symmetric first-order scalar equations with two delays in the nonlinearity, and (3) there always are restrictions on the possible flows near a double Hopf point for first-order scalar delay-differential equations with one delay in the nonlinearity, and in nth-order scalar delay-differential equations (n?2) with one delay feedback.     

The recognition of a class of bifurcation problems

In bifurcation theory there are two recognition problems concerning a given normal form, the recognition for the normal form and the recognition for universal unfoldings of bifurcation problems which are equivalent to the normal form. The two recognition problems for the normal forms εx²+δλ^k were only partially solved. In this paper we give a complete solution of the two problems for all k?1 uniformly.     

An Optimal-Time Algorithm for Shortest Paths on a Convex Polytope in Three Dimensions

We present an optimal-time algorithm for computing (an implicit representation of) the shortest-path map from a fixed source s on the surface of a convex polytope P in three dimensions. Our algorithm runs in O(nlog n) time and requires O(nlog n) space, where n is the number of edges of P. The algorithm is based on the O(nlog n) algorithm of Hershberger and Suri for shortest paths in the plane (Hershberger, J., Suri, S. in SIAM J. Comput. 28(6):2215–2256, 1999), and similarly follows the continuous Dijkstra paradigm, which propagates a “wavefront” from s along ∂ P. This is effected by generalizing the concept of conforming subdivision of the free space introduced by Hershberger and Suri and by adapting it for the case of a convex polytope in ℝ³, allowing the algorithm to accomplish the propagation in discrete steps, between the “transparent” edges of the subdivision. The algorithm constructs a dynamic version of Mount’s data structure (Mount, D.M. in Discrete Comput. Geom. 2:153–174, 1987) that implicitly encodes the shortest paths from s to all other points of the surface. This structure allows us to answer single-source shortest-path queries, where the length of the path, as well as its combinatorial type, can be reported in O(log n) time; the actual path can be reported in additional O(k) time, where k is the number of polytope edges crossed by the path. The algorithm generalizes to the case of m source points to yield an implicit representation of the geodesic Voronoi diagram of m sites on the surface of P, in time O((n+m)log (n+m)), so that the site closest to a query point can be reported in time O(log (n+m)). Work on this paper was supported by NSF Grants CCR-00-98246 and CCF-05-14079, by a grant from the U.S.-Israeli Binational Science Foundation, by grant 155/05 from the Israel Science Fund, and by the Hermann Minkowski–MINERVA Center for Geometry at Tel Aviv University. The paper is based on the Ph.D. Thesis of the first author, supervised by the second author. A preliminary version has been presented in Proc. 22nd Annu. ACM Sympos. Comput. Geom., pp. 30–39, 2006.