منابع مشابه
Topology of Conic Bundles - II
For conic bundles on a smooth variety (over a field of characteristic 6= 2) which degenerate into pairs of distinct lines over geometric points of a smooth divisor, we prove a theorem which relates the Brauer class of the non-degenerate conic on the complement of the divisor to the covering class (Kummer class) of the 2-sheeted cover of the divisor defined by the degenerate conic, via the Gysin...
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We discuss natural connections between three objects: quadratic forms with values in line bundles, conic bundles and quaternion orders. We use the even Clifford algebra, and the Brauer-Severi Variety, and other constructions to give natural bijections between these objects under appropriate hypothesis. We then restrict to a surface base and we express the second Chern class of the order in term...
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We study stable rationality properties of conic bundles over rational surfaces.
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P. Ellia and G.Sacchiero have shown that if S is a smooth surface in P which is ruled in conics, then S has degree 4 or 5 (cf. [ES]). In this paper we give a proof of this result combining the ideas of Ellia and Sacchiero as they are used in the paper of the second author on plane curve fibrations [Ra] and the recent work of G. Fløystad and the first author bounding the degree of smooth surface...
متن کاملOn Q-conic Bundles, Iii
A Q-conic bundle germ is a proper morphism from a threefold with only terminal singularities to the germ (Z ∋ o) of a normal surface such that fibers are connected and the anticanonical divisor is relatively ample. Building upon our previous paper [MP08a], we prove the existence of a Du Val anti-canonical member under the assumption that the central fiber is irreducible.
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ژورنال
عنوان ژورنال: Transformation Groups
سال: 2015
ISSN: 1083-4362,1531-586X
DOI: 10.1007/s00031-015-9342-9