共查询到20条相似文献,搜索用时 109 毫秒
1.
Adrian Ioana 《Inventiones Mathematicae》2011,185(1):55-73
We prove that if a countable group Γ contains a copy of
\mathbbF2\mathbb{F}_{2}, then it admits uncountably many non orbit equivalent actions. 相似文献
2.
R. N. Karasev 《Discrete and Computational Geometry》2010,44(2):429-438
We prove a result about partitioning an absolutely continuous measure in ℝ
d
into 2d equal parts by a system of cones with common vertex, where d is an odd prime power. The proof is topological and based on the calculation of the equivariant Euler class of a certain
vector bundle. 相似文献
3.
Michael I. Hartley 《Discrete and Computational Geometry》2010,44(4):844-859
One key problem in the theory of abstract polytopes is the so-called amalgamation problem. In its most general form, this is the problem of characterising the polytopes with given facets $\mathcal {K}$ and vertex figures ?. The first step in solving it for particular $\mathcal{K}$ and ? is to find the universal such polytope, which covers all the others. This article explains a construction that may be attempted on an arbitrary polytope ?, which often yields an infinite family of finite polytopes covering ? and sharing its facets and vertex figures. The existence of such an infinite family proves that the universal polytope is infinite; alternatively, the construction can produce an explicit example of an infinite polytope of the desired type. An algorithm for attempting the construction is explained, along with sufficient conditions for it to work. The construction is applied to a few $\mathcal{K}$ and ? for which it was previously not known whether or not the universal polytope was infinite, or for which only a finite number of finite polytopes was previously known. It is conjectured that the construction is quite broadly applicable. 相似文献
4.
The paper is devoted to the generalization of Lusztig’s q-analog of weight multiplicities to the Lie superalgebras $\mathfrak{gl}(n,m)$ and $\mathfrak{spo(}2n,M).$ We define such q-analogs K λ,μ (q) for the typical modules and for the irreducible covariant tensor $\mathfrak{gl}(n,m)$ -modules of highest weight λ. For $\mathfrak{gl}(n,m),$ the defined polynomials have nonnegative integer coefficients if the weight μ is dominant. For $\mathfrak{spo(}2n,M)$ , we show that the positivity property holds when μ is dominant and sufficiently far from a specific wall of the fundamental chamber. We also establish that the q-analog associated to an irreducible covariant tensor $\mathfrak{gl}(n,m)$ -module of highest weight λ and a dominant weight μ is the generating series of a simple statistic on the set of semistandard hook-tableaux of shape λ and weight μ. This statistic can be regarded as a super analog of the charge statistic defined by Lascoux and Schützenberger. 相似文献
5.
Raul Antonio Ferraz 《代数通讯》2013,41(2):851-872
The goal of this article is to describe a multiplicatively independent set, which generates the group of units of the integral group ring ?G, where G is either the cyclic group of order 2p or C2 × C2 × Cp, for a prime number p that satisfies some suitable conditions that will be specified later. 相似文献
6.
7.
Julia Porcino 《代数通讯》2015,43(1):84-101
We analyze the structure of ideals generated by some classes of 2 × 2 permanents of hypermatrices, generalizing [9] on 2 × 2 permanental ideals of generic matrices. We compare the obtained structure to that of the corresponding determinantal ideals in [11]: as expected, the permanental ideals have many more (minimal) components. In the last two sections, we examine a few related classes of permanental ideals. 相似文献
8.
本文中, 我们主要刻画了Toeplitz算子$T=M_{z^k}+M^*_{z^l}$的约化子空间, 其中 $k_i, l_i$ ($i=1,2$) 均是正整数, $k=(k_1,k_2), l=(l_1,l_2)$ 且 $k\neq l$, $M_{z^k}$, $M_{z^l}$ 是双圆盘加权Hardy空间$\mathcal{H}_\omega^2(\mathbb{D}^2)$上的乘法算子. 对权系数 $\omega$ 适当限制, 我们证明了由 $z^m$ 生成的 $T$ 的约化子空间均是极小的. 特别地, Bergman 空间和加权 Dirichlet 空间 $\mathcal{D}_\delta(\mathbb{D}^2)(\delta>0)$ 均是满足该限制条件的加权Hardy空间. 作为应用, 我们刻画了 $\mathcal{D}_\delta(\mathbb{D}^2)(\delta>0)$ 上 Toeplitz 算子 $T_{z^k+\bar{z}^l}$ 的约化子空间, 该结论是对双圆盘Bergman 空间上相关结论的推广. 相似文献
9.
Attila Nagy 《Semigroup Forum》2009,78(1):68-76
A semigroup S is said to be ℛ-commutative if, for all elements a,b∈S, there is an element x∈S
1 such that ab=bax. A semigroup S is called a generalized conditionally commutative (briefly,
-commutative) semigroup if it satisfies the identity aba
2=a
2
ba. An ℛ-commutative and
-commutative semigroup is called an
-commutative semigroup. A semigroup S is said to be a right H-semigroup if every right congruence of S is a congruence of S. In this paper we characterize the subdirectly irreducible semigroups in the class of
-commutative right H-semigroups.
Research supported by the Hungarian NFSR grant No T029525. 相似文献
10.
The paper is devoted to the realization of collections of spectral multiplicities for ergodic ?2-actions. Sufficient conditions ensuring the realizability of multiplicities of the form {2, 4, …, 2 n } are given. 相似文献
11.
12.
Trae Holcomb 《代数通讯》2013,41(7):2928-2938
This paper investigates numerical semigroups that yield 2 × 2 bricks. We demonstrate the existence of an infinite family of 2 × 2 bricks that includes all of the perfect 2 × 2 bricks. We provide a formula for the Frobenius numbers of these semigroups as well as a necessary and sufficient condition for the semigroups to be symmetric. 相似文献
13.
Rade T. Živaljević 《Discrete and Computational Geometry》2009,41(1):135-161
This paper lays the foundation for a theory of combinatorial groupoids that allows us to use concepts like “holonomy”, “parallel transport”, “bundles”, “combinatorial curvature”, etc. in the context
of simplicial (polyhedral) complexes, posets, graphs, polytopes and other combinatorial objects. We introduce a new, holonomy-type
invariant for cubical complexes, leading to a combinatorial “Theorema Egregium” for cubical complexes that are non-embeddable
into cubical lattices. Parallel transport of Hom-complexes and maps is used as a tool to extend Babson–Kozlov–Lovász graph coloring results to more general statements about
nondegenerate maps (colorings) of simplicial complexes and graphs.
The author was supported by grants 144014 and 144026 of the Serbian Ministry of Science and Technology. 相似文献
14.
Let G be the group of projectivities stabilizing a unital \(\mathcal{U}\) in \(\mathop{\mathrm{PG}}(2,q^{2})\) and let A,B be two distinct points of \(\mathcal{U}\). In this paper we prove that, if G has an elation group of order q with center A and a group of projectivities stabilizing both A and B of order a divisor of q?1 greater than \(2(\sqrt{q}-1)\), then \(\mathcal{U}\) is an ovoidal Buekenhout–Metz unital. From this result two group theoretic characterizations of orthogonal Buekenhout–Metz unitals are given. 相似文献
15.
Bart De Bruyn 《Journal of Algebraic Combinatorics》2009,30(4):567-584
Let \({\mathbb{K}}\) be a perfect field of characteristic 2. In this paper, we classify all hyperplanes of the symplectic dual polar space \(DW(5,{\mathbb{K}})\) that arise from its Grassmann embedding. We show that the number of isomorphism classes of such hyperplanes is equal to 5+N, where N is the number of equivalence classes of the following equivalence relation R on the set \(\{\lambda\in {\mathbb{K}}\,|\,X^{2}+\lambda X+1\mbox{ isirreducible}\) \(\mbox{in }{\mathbb{K}}[X]\}\): (λ 1,λ 2)∈R whenever there exists an automorphism σ of \({\mathbb{K}}\) and an \(a\in {\mathbb{K}}\) such that (λ 2 σ )?1=λ 1 ?1 +a 2+a. 相似文献
16.
设 $p\geq 7$ 为任意奇素数. 证明了当 $3\leq s
相似文献
17.
Ping Li 《Archiv der Mathematik》2013,101(5):495-499
The cohomology ring of any compact Kähler manifold gives rise to an ${SL(2, \mathbb{C})}$ -representation. In this short note, we show that the character of this representation essentially is the Poincaré polynomial of this Kähler manifold, which gives a natural interpretation of the Poincaré polynomial for Kähler manifolds. Our result is an analogue to an interpretation of the χ y genus for holomorphic symplectic manifolds due to George Thompson. 相似文献
18.
Koichi Betsumiya T. Aaron Gulliver Masaaki Harada 《Designs, Codes and Cryptography》2003,28(2):171-186
In this paper, it is shown that extremal (Hermitian) self-dual codes over
2 ×
2 exist only for lengths 1, 2, 3, 4, 5, 8 and 10. All extremal self-dual codes over
2 ×
2 are found. In particular, it is shown that there is a unique extremal self-dual code up to equivalence for lengths 8 and 10. Optimal self-dual codes are also investigated. A classification is given for binary [12, 7, 4] codes with dual distance 4, binary [13, 7, 4] codes with dual distance 4 and binary [13, 8, 4] codes with dual distance 4. 相似文献
19.
The dynamical behavior of a delayed neural network with bi-directional coupling is investigated by taking the delay as the
bifurcating parameter. Some parameter regions are given for conditional/absolute stability and Hopf bifurcations by using
the theory of functional differential equations. As the propagation time delay in the coupling varies, stability switches
for the trivial solution are found. Conditions ensuring the stability and direction of the Hopf bifurcation are determined
by applying the normal form theory and the center manifold theorem. We also discuss the spatio-temporal patterns of bifurcating
periodic oscillations by using the symmetric bifurcation theory of delay differential equations combined with representation
theory of Lie groups. In particular, we obtain that the spatio-temporal patterns of bifurcating periodic oscillations will
alternate according to the change of the propagation time delay in the coupling, i.e., different ranges of delays correspond
to different patterns of neural activities. Numerical simulations are given to illustrate the obtained results and show the
existence of bursts in some interval of the time for large enough delay. 相似文献
20.
本文探讨模同态广义逆在环模理论中的应用.利用模同态的{1}-逆与{2}-逆,分别给出了一类环及一类重要模的特征刻画. 相似文献