homotopy obstruction

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• Obstruction theory — In mathematics, obstruction theory is a name given to two different mathematical theories, both of which yield cohomological invariants. Contents 1 In homotopy theory 2 In geometric topology 3 In surgery theory …   Wikipedia

• Surgery theory — In mathematics, specifically in geometric topology, surgery theory is a collection of techniques used to produce one manifold from another in a controlled way, introduced by Milnor (1961). Surgery refers to cutting out parts of the manifold… …   Wikipedia

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• Normal invariant — In mathematics, a normal map is a concept in geometric topology due to William Browder which is of fundamental importance in surgery theory. Given a Poincaré complex X, a normal map on X endows the space, roughly speaking, with some of the… …   Wikipedia

• Stable normal bundle — In surgery theory, a branch of mathematics, the stable normal bundle of a differentiable manifold is an invariant which encodes the stable normal (dually, tangential) data. It is also called the Spivak normal bundle, after Michael Spivak… …   Wikipedia

• Whitehead torsion — In mathematics, Whitehead torsion is an invariant of an h cobordism in a Whitehead group, that is important in simple homotopy theory and surgery theory. It is named for J. H. C. Whitehead.Whitehead torsionSuppose that W is an h cobordism from M… …   Wikipedia

• Michael J. Hopkins — Mike Hopkins in Oberwolfach 2009 Born April 18, 1958 …   Wikipedia

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• Closed and exact differential forms — In mathematics, especially vector calculus and differential topology, a closed form is a differential form α whose exterior derivative is zero (dα = 0), and an exact form is a differential form that is the exterior derivative of another …   Wikipedia