منابع مشابه
A Note on Discrete Conduché Fibrations
The class of functors known as discrete Conduché fibrations forms a common generalization of discrete fibrations and discrete opfibrations, and shares many of the formal properties of these two classes. F. Lamarche [7] conjectured that, for any small category B, the category DCF/B of discrete Conduché fibrations over B should be a topos. In this note we show that, although for suitable categori...
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Let O be a discrete valuation ring with residue field k of characteristic 0. We denote by K the quotient field of O. A model of a variety XK defined over K is a flat scheme X defined over Spec O whose generic fiber is isomorphic to XK . Fano fibrations are models of smooth Fano varieties defined over K. In particular, del Pezzo fibrations of degree d are models of smooth del Pezzo surfaces of d...
متن کاملA Note on Affine Quotients and Equivariant Double Fibrations
We consider two linear algebraic groups G and G over the field of complex numbers, both of which are reductive. Take a finite dimensional rational representation W of G × G. Let Y = W//G := SpecC[W ] and X = W//G := SpecC[W ] ′ be the affine quotients. Since the action of G and G commutes on W , the quotient space X (respectively Y ) naturally inherits the action of G (respectively G). In this ...
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The purpose of this paper is to extend the results in [11] in the case of del Pezzo fibrations of degree 1. To this end we investigate the anticanonical linear systems of del Pezzo surfaces of degree 1. We then classify all possible effective anticanonical divisors on Gorenstein del Pezzo surfaces of degree 1 with canonical singularities. Mathematical Subject Classification (2000). 14D06, 14E05...
متن کاملDiagonal Fibrations Are Pointwise Fibrations
On the category of bisimplicial sets there are different Quillen closed model structures associated to various definitions of fibrations. In one of them, which is due to Bousfield and Kan and that consists of seeing a bisimplicial set as a simplicial object in the category of simplicial sets, fibrations are those bisimplicial set maps such that each of the induced simplicial set maps is a Kan f...
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ژورنال
عنوان ژورنال: Proceedings of the American Mathematical Society
سال: 1972
ISSN: 0002-9939
DOI: 10.1090/s0002-9939-1972-0423336-x