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路长至少为4的一个Menger型定理
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作者 杜清晏 《内蒙古大学学报(自然科学版)》 CAS CSCD 1991年第1期16-21,共6页
设G是简单图,HV(G),x,y∈V(G)\H。若G中任何一条长度不小于n的x-y路至少与H有一个交点。则记为(x,H,y)_G^4。本文证明了:若(x,H,y)_G ~4蕴涵|H|≥h,则G中至少存在{h/6}条长度不小于4且相互独立的x-y路。从而对n-4。改进了L.Montcjano和V... 设G是简单图,HV(G),x,y∈V(G)\H。若G中任何一条长度不小于n的x-y路至少与H有一个交点。则记为(x,H,y)_G^4。本文证明了:若(x,H,y)_G ~4蕴涵|H|≥h,则G中至少存在{h/6}条长度不小于4且相互独立的x-y路。从而对n-4。改进了L.Montcjano和V.Ncumann—Lara的结果。 展开更多
关键词 x-y 独立 路等价类 简单图
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On the classification of OADP varieties 被引量:1
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作者 CILIBERTO Ciro RUSSO Francesco 《Science China Mathematics》 SCIE 2011年第8期1561-1575,共15页
The main purpose of this paper is to show that OADP varieties stand at an important crossroad of various main streets in different disciplines like projective geometry,birational geometry and algebra.This is a good re... The main purpose of this paper is to show that OADP varieties stand at an important crossroad of various main streets in different disciplines like projective geometry,birational geometry and algebra.This is a good reason for studying and classifying them.Main specific results are:(a) the classification of all OADP surfaces (regardless to their smoothness);(b) the classification of a relevant class of normal OADP varieties of any dimension,which includes interesting examples like lagrangian grassmannians.Following Pirio and Russo (Comm Math Helv,to appear),the equivalence of the classification in (b) with the one of quadro-quadric Cremona transformations and of complex,unitary,cubic Jordan algebras are explained. 展开更多
关键词 apparent double points tangential projective cubic Jordan algebra
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