منابع مشابه
Stable Rationality and Conic Bundles
We study stable rationality properties of conic bundles over rational surfaces.
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برد عددی ماتریس مربعی a را با w(a) نشان داده و به این صورت تعریف می کنیم w(a)={x8ax:x ?s1} ، که در آن s1 گوی واحد است. در سال 2009، راسل کاردن مساله برد عددی معکوس را به این صورت مطرح کرده است : برای نقطه z?w(a)، بردار x?s1 را به گونه ای می یابیم که z=x*ax، در این پایان نامه ، الگوریتمی برای حل مساله برد عددی معکوس ارانه می دهیم.
15 صفحه اولConic bundles and Clifford algebras
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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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...
متن کاملConic bundles in projective fourspace
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...
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ژورنال
عنوان ژورنال: Russian Mathematical Surveys
سال: 2018
ISSN: 0036-0279,1468-4829
DOI: 10.1070/rm9811