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Characteristic class

In mathematics, a characteristic class is a way of associating to each principal bundle of X a cohomology class of X. The cohomology class measures the extent the bundle is "twisted" — and whether it possesses sections. Characteristic classes are global invariants that measure the deviation of a local product structure from a global product structure. They are one of the unifying geometric concepts in algebraic topology, differential geometry, and algebraic geometry.

The notion of characteristic class arose in 1935 in the work of Eduard Stiefel and Hassler Whitneyabout vector fields on manifolds.
 

Arese (Lombard: Ares [aˈreːs]) is a comune (municipality) in the Metropolitan City of Milan in the Italian region Lombardy, located about 12 kilometres (7 mi) northwest of Milan.

Arese borders the following municipalities: Lainate, Garbagnate Milanese, Bollate, Rho, Milan.

Arese received the honorary title of city with a presidential decree of October 25, 1985.

For what concerns the historical center, of particular interest is the Church of St. Peter and Paul, located in the city center.
 
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