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71.
S. Yu. Orevkov 《Mathematical Notes》1996,60(2):153-164
An example of a three-sheeted covering over the ball in 2 is constructed. The covering is the union of a four-dimensional ball with an analytic disk. The projection of the ball is a local homeomorphism ramified along the disk, whose projection is a part of an algebraic curve.Translated fromMatematicheskie Zametki, Vol. 60, No. 2, pp. 206–224, August, 1996.This research was partially supported by the Russian Foundation for Basic Research under grant No. 93-011-225. 相似文献
72.
Edoardo Ballico Giorgio Bolondi Philippe Ellia Rosa Maria Mirò -Roig 《Transactions of the American Mathematical Society》1997,349(11):4589-4608
In this paper we show the existence of smooth connected space curves not contained in a surface of degree less than , with genus maximal with respect to the degree, in half of the so-called range A. The main tool is a technique of deformation of stick-figures due to G. Fløystad.
73.
In this paper we prove that the generalized permutation graph G(n,k) is upper embeddable if it has at most two odd subcycles,and that the maximum genus of G(n,k) is more than[β(G(n,k))/3]in most cases. 相似文献
74.
Some results about the genus distributions of graphs are known,but little is known about those of digraphs.In this paper,the method of joint trees initiated by Liu is generalized to compute the embedding genus distributions of digraphs in orientable surfaces.The genus polynomials for a new kind of 4-regular digraphs called the cross-ladders in orientable surfaces are obtained.These results are close to solving the third problem given by Bonnington et al. 相似文献
75.
二阶离散Hamiltonian系统的多重周期解 总被引:2,自引:0,他引:2
利用变分原理和Clark定理,研究了带参数的二阶离散Hamiltonian系统的多重周期解,得到了此类方程周期解个数的下界估计. 相似文献
76.
ZHAO Xu''''an GAO Hongzhu & QIU Huaidong LMAM School of Mathematics Science Beijing Normal University Beijing China 《中国科学A辑(英文版)》2006,49(9)
There are three key ingredients in the study of the minimal genus problem for rational surfaces CP2#nCP2: the generalized adjunction formula, the action of the orthogonal group of the Lorentz space and the geometric construction. In this paper, we prove the uniqueness of the standard form (see Definition 1.1 and Theorem 1.1) of a 2-dimensional homology class under the action of the subgroup of the Lorentz orthogonal group that is realized by the diffeomorphisms of CP2#nCP2.Using the geometric construction, we determine the minimal genera of some classes (see Theorem 1.2). 相似文献
77.
A well‐known conjecture in topological graph theory says that the genus distribution of every graph is log‐concave. In this paper, the genus distribution of the circular ladder is re‐derived, using overlap matrices and Chebyshev polynomials, which facilitates proof that this genus distribution is log‐concave. 相似文献
78.
Al3-manifOldsandsurfacesconsideredinthisPaperareassumedtobecompactandori-entable,andallconcePtsandnotationsnotdefinedinthepaperareStandardfsee,forexample[2,3j.AcompressionbodyHisconstructedbyadding2-handlestoSXIalongacollectionofpairwisdisjointsimpleclosedcurvesonSX{o},andcaPpingoffanyresulting2-spherebound-arycomponentSwith3-balls,whereSisaconnectedclosedorientablesurface.ThecomponentSX{1}Of8Hisdenoted8 Handthesurface8H-8 H,whichmayormaynotbeconnect-ed,isdenoted8H.If8H=gi,Hisahandleb… 相似文献
79.
Let M be a connected orientable compact irreducible 3-manifold. Suppose that αM consists of two homeomorphic surfaces F1 and F2, and both F1 and F2 are compressible in M. Suppose furthermore that g(M, F1) = g(M) + g(F1), where g(M, F1)is the Heegaard genus of M relative to F1. Let Mfbe the closed orientable 3-manifold obtained by identifying F1 and F2 using a homeomorphism f : F1 → F2. The authors show that if f is sufficiently complicated, then g(Mf) = g(M, αM) + 1. 相似文献
80.
In this paper a method is given to calculate the explicit expressions of embedding genus distribution for ladder type graphs
and cross type graphs. As an example, we refind the genus distribution of the graph J
n
which is the first class of graphs studied for genus distribution where its genus depends on n.
This work was supported National Natural Science Foundation of China (Grant Nos. 10571013, 60433050) and the State Key Development
Program of Basic Research of China (Grant No. 2004CB318004) 相似文献