Almost Split Sequences for Rational Double Points
نویسندگان
چکیده
منابع مشابه
On F -Almost Split Sequences
Let Λ be an Artinian algebra and F an additive subbifunctor of ExtΛ(−,−) having enough projectives and injectives. We prove that the dualizing subvarieties of mod Λ closed under F -extensions have F -almost split sequences. Let T be an F -cotilting module in mod Λ and S a cotilting module over Γ = End(T ). Then Hom(−, T ) induces a duality between F -almost split sequences in ⊥F T and almost sp...
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For a commutative algebraic group G over a perfect field k, Ribet defined the set of almost rational torsion points G tors,k of G over k. For positive integers d, g, we show there is an integer Ud,g such that for all tori T of dimension at most d over number fields of degree at most g, T ar tors,k ⊆ T [Ud,g]. We show the corresponding result for abelian varieties with complex multiplication, an...
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We show that almost split sequences in the category of comodules over a coalgebra Γ with finite-dimensional right-hand term are direct limits of almost split sequences over finite dimensional subcoalgebras. In previous work we showed that such almost split sequences exist if the right hand term has a quasifinitely copresented linear dual. Conversely, taking limits of almost split sequences over...
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ژورنال
عنوان ژورنال: Transactions of the American Mathematical Society
سال: 1987
ISSN: 0002-9947
DOI: 10.2307/2000898