%0 Journal Article
%T IMMERSED SPHERES IN INDEFINITE 4-MANIFOLDS<br>非正(负)定四维流形中的浸入球
%A GAO HONG-ZHU
%A <br>高红铸
%J 系统科学与数学
%D 1993
%I 
%X The minimal number of double points of immersed 2-spheres in indefinite 4-manifoldsCP~2 #m \bar{CP^2} is studied and a lower bound is given.Combining with the action of orthogonalgroups,a complete answer is given to whether a 2-dimensional homology class with positivesquare can be represented by an embedded sphere for m=2 or 3.The representability of someinteresting cases is also proved for general m.
%U http://www.alljournals.cn/get_abstract_url.aspx?pcid=6E709DC38FA1D09A4B578DD0906875B5B44D4D294832BB8E&cid=37F46C35E03B4B86&jid=0CD45CC5E994895A7F41A783D4235EC2&aid=87445089EBAB63F038D69D20131120B0&yid=D418FDC97F7C2EBA&vid=FC0714F8D2EB605D&iid=E158A972A605785F&sid=0918129209B14F3E&eid=A7AE820C12CC9AD3&journal_id=1000-0577&journal_name=系统科学与数学&referenced_num=0&reference_num=0