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Institut Henri Poincaré


À la redécouverte des points rationnels

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Cohomological obstructions to local-global principles

Cyril Demarche

Hasse proved that for quadrics the existence of rational points reduces to the existence of solutions over local fields. In many cases, cohomological constructions provide obstructions to such a local to global principle. The objective of these lectures is to give an introduction to these cohomological tools.