共查询到20条相似文献,搜索用时 15 毫秒
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Beatriz Pascual-Escudero 《Journal of Pure and Applied Algebra》2019,223(6):2598-2614
Let X be an algebraic variety defined over a field of characteristic zero, and let be a point in the closed subset of maximum multiplicity of X. We provide a criterion, given in terms of arcs, to determine whether ξ is isolated in . More precisely, we use invariants of arcs derived from the Nash multiplicity sequence to characterize when ξ is an isolated point in . 相似文献
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Imanol Mozo Carollo 《Journal of Pure and Applied Algebra》2021,225(2):106490
This paper approaches the construction of the universal completion of the Riesz space of continuous real functions on a completely regular frame L in two different ways. Firstly as the space of continuous real functions on the Booleanization of L. Secondly as the space of nearly finite Hausdorff continuous functions on L. The former has no counterpart in the classical theory, as the Booleanization of a spatial frame is not spatial in general, and it offers a lucid way of representing the universal completion as a space of continuous real functions. As a corollary we obtain that and have isomorphic universal completions if and only if the Booleanization of L and M are isomorphic and we characterize frames L such that is universally complete as almost Boolean frames. The application of this last result to the classical case of the space of continuous real functions on a topological space X characterizes those spaces X for which is universally complete. Finally, we present a pointfree version of the Maeda-Ogasawara-Vulikh representation theorem and use it to represent the universal completion of an Archimedean Riesz space with weak unit as a space of continuous real functions on a Boolean frame. 相似文献
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《Journal of Pure and Applied Algebra》2022,226(10):107074
For a commutative ring A we consider a related graph, , whose vertices are the unimodular rows of length 2 up to multiplication by units. We prove that is path-connected if and only if A is a -ring, in the terminology of P. M. Cohn. Furthermore, if denotes the clique complex of , we prove that is simply connected if and only if A is universal for . More precisely, our main theorem is that for any commutative ring A the fundamental group of is isomorphic to the group modulo the subgroup generated by symbols. 相似文献
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Ryotaro Tanaka 《Journal of Mathematical Analysis and Applications》2022,505(1):125444
A Banach space X is said to be isomorphic to another Y with respect to the structure of Birkhoff-James orthogonality, denoted by , if there exists a (possibly nonlinear) bijection between X and Y that preserves Birkhoff-James orthogonality in both directions. It is shown that if either X or Y is finite dimensional and , and that if . Moreover, if H is a Hilbert space with and , then . In the two-dimensional case, it turns out that , which indicates that nonlinear Birkhoff-James orthogonality preservers between Banach spaces are not necessarily scalar multiples of isometric isomorphisms. 相似文献
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《Operations Research Letters》2023,51(5):477-482
Given a set of n points in , the minimum-width cubic shell problem asks to find a thinnest cubic shell that encloses the input points, where a cubic shell refers to as a closed volume between two concentric axis-aligned cubes. In this paper, we improve the previous -time algorithm presented in Bae (2019) [6] to worst-case time. This is the first optimal-time algorithm to the problem. 相似文献
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Raymond C. Heitmann 《Journal of Pure and Applied Algebra》2022,226(1):106809
It is shown that if is a complete local domain with and is its integral closure in an algebraic closure of the quotient field, then both the -adic and p-adic completions of are integral domains. More generally, this theorem remains true if the completeness assumption is relaxed to allow R to be an analytically irreducible Henselian local ring. It is also shown that these rings, which are Cohen-Macaulay R-modules (even balanced in the -adic case), will have dimension larger than the dimension of R unless . 相似文献
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《Journal of Pure and Applied Algebra》2022,226(11):107101
We investigate nef and movable cones of hypersurfaces in Mori dream spaces. The first result is: Let Z be a smooth Mori dream space of dimension at least four whose extremal contractions are of fiber type of relative dimension at least two and let X be a smooth ample divisor in Z, then X is a Mori dream space as well.The second result is: Let Z be a Fano manifold of dimension at least four whose extremal contractions are of fiber type and let X be a smooth anti-canonical hypersurface in Z, which is a smooth Calabi–Yau variety, then the unique minimal model of X up to isomorphism is X itself, and moreover, the movable cone conjecture holds for X, namely, there exists a rational polyhedral cone which is a fundamental domain for the action of birational automorphisms on the effective movable cone of X.The third result is: Let be the N-fold self-product of the n-dimensional projective space. Let X be a general complete intersection of hypersurfaces of multidegree in P with . Then X has only finitely many minimal models up to isomorphism, and moreover, the movable cone conjecture holds for X. 相似文献
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Joaquín Moraga 《Journal of Pure and Applied Algebra》2019,223(8):3225-3237
In this note, we study linear systems on complete toric varieties X with an invariant point whose orbit under the action of contains the dense torus T of X. We give a characterization of such varieties in terms of its defining fan and introduce a new definition of expected dimension of linear systems which consider the contribution given by certain toric subvarieties. Finally, we study degenerations of linear systems on these toric varieties induced by toric degenerations. 相似文献