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本文对系统dxdt=-y(1-ax2n)(1-bx2n) δx-lx4n 1dydt=x2n-1(1-cx2n)(1-bx2n)进行定性分析,得出其极限环的存在性,不存在性及唯一性的一系列充分条件. 相似文献
3.
Derived Brackets 总被引:3,自引:1,他引:2
Yvette Kosmann-Schwarzbach 《Letters in Mathematical Physics》2004,69(1-3):61-87
We survey the many instances of derived bracket construction in differential geometry, Lie algebroid and Courant algebroid theories, and their properties. We recall and compare the constructions of Buttin and of Vinogradov, and we prove that the Vinogradov bracket is the skew-symmetrization of a derived bracket. Odd (resp., even) Poisson brackets on supermanifolds are derived brackets of canonical even (resp., odd) Poisson brackets on their cotangent bundle (resp., parity-reversed cotangent bundle). Lie algebras have analogous properties, and the theory of Lie algebroids unifies the results valid for manifolds on the one hand, and for Lie algebras on the other. We outline the role of derived brackets in the theory of Poisson structures with background'. 相似文献
4.
Let G be a graph and f : V(G)→{1,3,5,…}. Then a subgraph H of G is called a (1,f)-odd subgraph if degH(x){1,3,…,f(x)} for all xV(H). If f(x)=1 for all xV(G), then a (1,f)-odd subgraph is nothing but a matching. A (1,f)-odd subgraph H of G is said to be maximum if G has no (1,f)-odd subgraph K such that |K|>|H|. We show that (1,f)-odd subgraphs have some properties similar to those of matchings, in particular, we give a formula for the order of a maximum (1,f)-odd subgraph, which is similar to that for the order of a maximum matching. 相似文献
5.
朱晓颖 《纯粹数学与应用数学》2013,(6):609-614
寻找平面图是3-或者4-可选择的充分条件是图的染色理论中一个重要研究课题,本文研究了围长至少是4的特殊平面图的选择数,通过权转移的方法证明了每个围长至少是4且不合8-圈,9-圈和10-圈的平面图是3-可选择的. 相似文献
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7.
In this paper, we consider a kind of neutral functional differential equation as follows:
8.
王恺顺 《中国科学A辑(英文版)》2003,46(1):91-93
In this paper, it is proved that the girth of a 4-homogeneous bipartite graph with valency greater than 2 is at most 12. 相似文献
9.
Roland Wittje 《Physics in Perspective (PIP)》2007,9(4):406-433
In the late 1940s and the 1950s, Norwegian nuclear scientists, engineers, and administrators were deeply split over their
nation’s goals, organization, politics, and tools for research in nuclear physics. One faction was determined to build a nuclear
reactor in Norway, while another fiercely opposed the reactor plans and focused on particle accelerators. The first faction
comprised scientific entrepreneurs and research technologists, the second academic scientists, most of whom began their research
careers in nuclear physics in the 1930s. To understand this conflict, I trace the development of nuclear research in Norway
from the early 1930s to the mid-1950s, placing it within an international context.
Roland Wittje is working on his habilitation thesis in the History of Science Unit at the University of Regensburg, Germany. 相似文献
10.
David Défossez 《Discrete Mathematics》2008,308(11):2265-2268
In this note we prove a long-standing conjecture of Sterboul [P. Duchet, Hypergraphs, in: R. Graham, M. Grötschel, L. Lovász (Eds.), Handbook of Combinatorics, 1995, pp. 381-432 (Chapter 7)], which states that a hypergraph is bicolorable provided it does not contain a specific kind of odd cycle. This is currently the strongest result of its kind, improving on results by Berge [Graphs and Hypergraphs, North-Holland, American Elsevier, Amsterdam, 1973] and Fournier and Las Vergnas [Une classe d’hypergraphes bichromatiques II, Discrete Math. 7 (1974) 99-106; A class of bichromatic hypergraphs, Ann. Discrete Math. 21, in: C. Berge, V. Chvátal (Eds.), Topics on Perfect Graphs, 1984, pp. 21-27]. 相似文献