On the Second Cohomology Categorical Group and a Hochschild-serre 2-exact Sequence
نویسنده
چکیده
Résumé. We introduce the second cohomology categorical group of a categorical group G with coefficients in a symmetric G-categorical group and we show that it classifies extensions of G with symmetric kernel and a functorial section. Moreover, from an essentially surjective homomorphism of categorical groups we get 2-exact sequences à la Hochschild-Serre connecting the categorical groups of derivations and the first and the second cohomology categorical groups.
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