共查询到20条相似文献,搜索用时 31 毫秒
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One way of defining an oriented colouring of a directed graph is as a homomorphism from to a target directed graph , and an injective oriented colouring of can be defined as a homomorphism from to a target directed graph such that no two in-neighbours of a vertex of have the same image. Oriented colourings may be constructed using target directed graphs that are nice, as defined by Hell et al. (2001). We extend the work of Hell et al. by considering target graphs that are tournaments, characterizing nice tournaments, and proving that every nice tournament on vertices is -nice for some . We also give a characterization of tournaments that are nice but not injective-nice. 相似文献
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B. Narasimha Chary 《Journal of Pure and Applied Algebra》2018,222(9):2552-2561
Let G be a simple algebraic group over the field of complex numbers. Fix a maximal torus T and a Borel subgroup B of G containing T. Let w be an element of the Weyl group W of G, and let be the Bott–Samelson–Demazure–Hansen (BSDH) variety corresponding to a reduced expression of w with respect to the data .In this article we give complete characterization of the expressions such that the corresponding BSDH variety is Fano or weak Fano. As a consequence we prove vanishing theorems of the cohomology of tangent bundle of certain BSDH varieties and hence we get some local rigidity results. 相似文献
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In this work we analyze some topological properties of the remainder of the semialgebraic Stone–Cěch compactification of a semialgebraic set in order to ‘distinguish’ its points from those of M. To that end we prove that the set of points of that admit a metrizable neighborhood in equals where is the largest locally compact dense subset of M and is the closure in M of the set of 1-dimensional points of M. In addition, we analyze the properties of the sets and of free maximal ideals associated with formal and semialgebraic paths. We prove that both are dense subsets of the remainder ?M and that the differences and are also dense subsets of ?M. It holds moreover that all the points of have countable systems of neighborhoods in . 相似文献
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In this paper, we consider the Cauchy problem for a two-phase model with magnetic field in three dimensions. The global existence and uniqueness of strong solution as well as the time decay estimates in are obtained by introducing a new linearized system with respect to for constants and , and doing some new a priori estimates in Sobolev Spaces to get the uniform upper bound of in norm. 相似文献
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Davide Barbieri Carlos Cabrelli Eugenio Hernández Peter Luthy Ursula Molter Carolina Mosquera 《Comptes Rendus Mathematique》2018,356(1):107-113
In this note, we investigate the existence of frames of exponentials for in the setting of LCA groups. Our main result shows that sub-multitiling properties of with respect to a uniform lattice Γ of guarantee the existence of a frame of exponentials with frequencies in a finite number of translates of the annihilator of Γ. We also prove the converse of this result and provide conditions for the existence of these frames. These conditions extend recent results on Riesz bases of exponentials and multitilings to frames. 相似文献
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Indranil Biswas Subramaniam Senthamarai Kannan Donihakalu Shankar Nagaraj 《Comptes Rendus Mathematique》2017,355(4):452-454
Let be the wonderful compactification of a simple affine algebraic group G of adjoint type defined over . Let be the closure of a maximal torus . We prove that the group of all automorphisms of the variety is the semi-direct product , where is the normalizer of T in G and D is the group of all automorphisms of the Dynkin diagram, if . Note that if , then and so in this case . 相似文献
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