Extensions of Strictly Commutative Picard Stacks
نویسنده
چکیده
Let S be a site. We introduce the notion of extension of strictly commutative Picard S-stacks. Applying this notion to 1-motives, we get the notion of extension of 1-motives and we prove the following conjecture of Deligne: if MRZ(k) denotes the integral version of the neutral Tannakian category of mixed realizations over an algebraically closed field k, then the subcategory of MRZ(k) generated by 1-motives defined over k is stable under extensions.
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