Session 30. Real Algebraic Geometry, applications and related topics

Weight Filtrations for Real Algebraic Varieties

Adam ParusiƄski, Université Nice Sophia Antipolis, France
The talk is based on the joint work with Clint McCrory
For real algebraic varieties we define a functorial weight filtration on homologies with Z/2 coefficients. This filtration is an analog of Deligne's weight filtration for complex algebraic varieties and can be defined on classical homologies and on Borel-Moore homologies. We show that the weight filtration on Borel-Moore homologies is induced by a geometric functorial filtration on the complex of semialgebraic chains with closed supports. The associated spectral sequence gives non-trivial additive invariants of real algebraic varieties, the virtual Betti numbers. These additive invariants are used to classify the singularities of real analytic function germs by method of motivic integration.
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