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61.
Ebrahimi-Fard Kurusch José M. Gracia-Bondía Frédéric Patras 《Letters in Mathematical Physics》2007,81(1):61-75
The word problem for an arbitrary associative Rota–Baxter algebra is solved. This leads to a noncommutative generalization
of the classical Spitzer identities. Links to other combinatorial aspects are indicated.
相似文献
62.
Scaling symmetry of -type Drinfel’d–Sokolov hierarchy is investigated. Applying similarity reduction to the hierarchy, one can obtain the Schlesinger
equation with (n + 1) regular singularities. Especially in the case of n = 3, the hierarchy contains the three-wave resonant system and the similarity reduction gives the generic case of the Painlevé
VI equation. We also discuss Weyl group symmetry of the hierarchy.
相似文献
63.
64.
Zhen-Han Tu 《Mathematische Zeitschrift》2002,240(1):13-35
We prove that any proper holomorphic mapping from to is necessarily a totally geodesic isometric embedding with respect to their Bergman metrics and therefore is the standard
linear embedding up to their automorphisms. The proof of the main result in this paper will be achieved by a differential-geometric
study of a special class of complex geodesic curves on the bounded symmetric domains with respect to their Bergman metrics.
Received: 31 October 2000; in final form: 2 July 2001/ Published online: 4 April 2002 相似文献
65.
Ekkehard Krätzel 《Monatshefte für Mathematik》2002,137(3):197-211
In this article we investigate the number of lattice points in a three-dimensional convex body which contains non-isolated
points with Gaussian curvature zero but a finite number of flat points at the boundary. Especially, in case of rational tangential
planes in these points we investigate not only the influence of the flat points but also of the other points with Gaussian
curvature zero on the estimation of the lattice rest.
Received 19 June 2001; in revised form 17 January 2002
RID="a"
ID="a" Dedicated to Professor Edmund Hlawka on the occasion of his 85th birthday 相似文献
66.
Bruno Sévennec 《Mathematische Annalen》2002,324(1):195-211
We improve – roughly by a factor 2 – the known bound on the multiplicity of the second eigenvalue of Schr?dinger operators
(i.e. Laplace plus potential) on closed surfaces. This gives four new topological types of surfaces for which Colin de Verdière's
conjecture relating the maximal multiplicity to the chromatic number of the surface is verified. The proof goes by defining
a space of "nodal splittings” of the surface, equipped with a double covering to which a Borsuk-Ulam type theorem is applied.
Received: 19 June 2001; revised version: 18 March 2002 /Published online: 17 June 2002 相似文献
67.
Michael Capalbo 《Combinatorica》2002,22(3):345-359
For all positive integers N and k, let denote the family of planar graphs on N or fewer vertices, and with maximum degree k. For all positive integers N and k, we construct a -universal graph of size . This construction answers with an explicit construction the previously open question of the existence of such a graph.
Received July 8, 1998
RID="*"
ID="*" Supported by NSF grant CCR98210-58 and ARO grant DAAH04-96-1-0013. 相似文献
68.
Dedicated to the memory of Paul Erdős
A graph is called -free if it contains no cycle of length four as an induced subgraph. We prove that if a -free graph has n vertices and at least edges then it has a complete subgraph of vertices, where depends only on . We also give estimates on and show that a similar result does not hold for H-free graphs––unless H is an induced subgraph of . The best value of is determined for chordal graphs.
Received October 25, 1999
RID="*"
ID="*" Supported by OTKA grant T029074.
RID="**"
ID="**" Supported by TKI grant stochastics@TUB and by OTKA grant T026203. 相似文献
69.
Improved Bounds for Acyclic Job Shop Scheduling 总被引:2,自引:0,他引:2
In acyclic job shop scheduling problems there are n jobs and m machines. Each job is composed of a sequence of operations to be performed on different machines. A legal schedule is one
in which within each job, operations are carried out in order, and each machine performs at most one operation in any unit
of time. If D denotes the length of the longest job, and C denotes the number of time units requested by all jobs on the most loaded machine, then clearly lb = max[C,D] is a lower bound on the length of the shortest legal schedule. A celebrated result of Leighton, Maggs, and Rao shows that
if all operations are of unit length, then there always is a legal schedule of length O(lb), independent of n and m. For the case that operations may have different lengths, Shmoys, Stein and Wein showed that there always is a legal schedule
of length , where the notation is used to suppress terms. We improve the upper bound to . We also show that our new upper bound is essentially best possible, by proving the existence of instances of acyclic job
shop scheduling for which the shortest legal schedule is of length . This resolves (negatively) a known open problem of whether the linear upper bound of Leighton, Maggs, and Rao applies to
arbitrary job shop scheduling instances (without the restriction to acyclicity and unit length operations).
Received June 30, 1998
RID="*"
ID="*" Incumbent of the Joseph and Celia Reskin Career Development Chair
RID="†"
ID="†" Research was done while staying at the Weizmann Institute, supported by a scholarship from the Minerva foundation. 相似文献
70.
Alexandr V. Kostochka 《Combinatorica》2002,22(2):275-285
Dedicated to the memory of Paul Erdős
Let f(r,p,t) (p > t >= 1, r >= 2) be the maximum of the cardinality of a minimum transversal over all r-uniform hypergraphs possessing the property that every subhypergraph of with p edges has a transversal of size t. The values of f(r,p,2) for p = 3, 4, 5, 6 were found in [1] and bounds on f(r,7,2) are given in [3]. Here we prove that for large p and huge r.
Received September 23, 1999
RID="*"
ID="*" This work was partially supported by the grant 99-01-00581 of the Russian Foundation for Fundamental Research and the
Dutch–Russian Grant NWO-047-008-006. 相似文献