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arXiv 1206.4271math.AGmath.AT
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实central projections阶的一个过壁公式

A wall crossing formula for degrees of real central projections

Christian Okonek, Andrei Teleman

摘要:

主要结果是定义在实射影空间子流形上的中心投影的一个过壁公式。我们的公式给出了当投影的中心变化时,这种投影的阶的跳跃。次数依赖于投影的事实是一个新的现象,是实代数几何特有的。我们在许多有趣的情况下说明了这一现象。我们所考虑的映射类的关键假设是相对可定向性,这个条件允许我们以连贯的方式定义$\Z$值度映射。最后,我们的文章与几个例子,例如,与商,Wronski地图,和一个新版本的真正的子空间问题的极点配置映射。

英文摘要:

The main result is a wall crossing formula for central projections defined on submanifolds of a real projective space. Our formula gives the jump of the degree of such a projection when the center of the projection varies. The fact that the degree depends on the projection is a new phenomenon, specific to real algebraic geometry. We illustrate this phenomenon in many interesting situations. The crucial assumption on the class of maps we consider is relative orientability, a condition which allows us to define a $\Z$-valued degree map in a coherent way. We end the article with several examples, e.g. the pole placement map associated with a quotient, the Wronski map, and a new version of the real subspace problem.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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