排序方式: 共有30条查询结果,搜索用时 31 毫秒
11.
We construct an explicit bundle with flat connection on the configuration space of n points on a complex curve. This enables one to recover the ‘1-formality’ isomorphism between the Lie algebra of the prounipotent completion of the pure braid group of n points on a surface and an explicitly presented Lie algebra, and to extend it to a morphism from the full braid group of the surface to the semidirect product of the associated group with the symmetric group Sn. 相似文献
12.
A group G is called an A-group, where A is a given Abelian group, if it comes equipped with an action of A on G which mimics the way in which Z acts on any group. This action is codified in terms of certain axioms, all but one of which were introduced some years ago by R. C. Lyndon. For every such G and A there exists an A-exponential group G
A
which is the A-completion of G. We prove here that if G is a torsion-free hyperbolic group and if A is a torsion-free Abelian group, then the Lyndon's type completion G
A
of G is G-discriminated by G. This implies various model-theoretic and algorithmic results about G
A
. 相似文献
13.
首先引入了相通连续Domain的概念,利用主理想及连通闭集刻画了相通连续Domain; 其次考察了相通完备偏序集的定向完备化,得到了一些好的结果. 相似文献
14.
Charles R. Johnson Brenda Kroschel Henry Wolkowicz 《Computational Optimization and Applications》1998,9(2):175-190
Given a nonnegative, symmetric matrix of weights, H, we study the problem of finding an Hermitian, positive semidefinite matrix which is closest to a given Hermitian matrix, A, with respect to the weighting H. This extends the notion of exact matrix completion problems in that, H
ij
=0 corresponds to the element A
ij
being unspecified (free), while H
ij
large in absolute value corresponds to the element A
ij
being approximately specified (fixed).We present optimality conditions, duality theory, and two primal-dual interior-point algorithms. Because of sparsity considerations, the dual-step-first algorithm is more efficient for a large number of free elements, while the primal-step-first algorithm is more efficient for a large number of fixed elements.Included are numerical tests that illustrate the efficiency and robustness of the algorithms 相似文献
15.
Guitart and Lair have established the existence of Locally Free Diagrams, which can be seen as a purely categorical version of the solution set condition, and of the Lowenheim–Skolem theorem. Their proof is based on a transfinite construction by saturation. An iterative principle is established, but the construction is not effective for every step. The thesis of Gerner contains a more effective proof for the existence of Locally Free Diagrams (with the restriction that the projective bases of the sketch S must all be finite). But the problem of lies in the impossibility to name concretely the elements of the Locally Free Diagrams. The present paper will provide a new construction of the Locally Free Diagram in which the effective and the non-effective part will be much more separated (again the projective bases must all be finite). This construction represents a notable improvement with regard to the proof of allowing the concrete designation of the elements ofthe Locally Free Diagrams. Furthermore we show that the construction is relatively filtered (i.e. satisfies the filtered-property). 相似文献
16.
17.
Fred Richman 《Mathematical Logic Quarterly》2008,54(1):98-108
A notion of completeness and completion suitable for use in the absence of countable choice is developed. This encompasses the construction of the real numbers as well as the completion of an arbitrary metric space. The real numbers are characterized as a complete Archimedean Heyting field, a terminal object in the category of Archimedean Heyting fields. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
18.
Pinar Heggernes 《Discrete Applied Mathematics》2009,157(9):2057-2069
We present an algorithm that supports operations for modifying a split graph by adding edges or vertices and deleting edges, such that after each modification the graph is repaired to become a split graph in a minimal way. In particular, if the graph is not split after the modification, the algorithm computes a minimal, or if desired even a minimum, split completion or deletion of the modified graph. The motivation for such operations is similar to the motivation for fully dynamic algorithms for particular graph classes. In our case we allow all modifications to the graph and repair, rather than allowing only the modifications that keep the graph split. Fully dynamic algorithms of the latter kind are known for split graphs [L. Ibarra, Fully dynamic algorithms for chordal graphs and split graphs, Technical Report DCS-262-IR, University of Victoria, Canada, 2000].Our results can be used to design linear time algorithms for some recognition and completion problems, where the input is supplied in an on-line fashion. 相似文献
19.
KennethJohnHARRISON 《数学学报(英文版)》2003,19(3):577-590
In a matrix-completion problem the aim is to specifiy the missing entries of a matrix in order to produce a matrix with particular properties. In this paper we survey results concerning matrix-completion problems where we look for completions of various types for partial matrices supported on a given pattern. We see that the existence of completions of the required type often depends on the chordal properties of graphs associated with the pattern. 相似文献
20.
《Journal of Pure and Applied Algebra》2022,226(8):107029
We give a 3-universal property for the Karoubi envelope of a 2-category. Using this, we show that the 3-categories of finite semisimple 2-categories (as introduced in [1]) and of multifusion categories are equivalent. 相似文献