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931.
Benoit Loridant 《Topology and its Applications》2008,155(7):667-695
Let be a root of the polynomial p(x)=x2+4x+5. It is well known that the pair (p(x),{0,1,2,3,4}) forms a canonical number system, i.e., that each x∈Z[α] admits a finite representation of the shape x=a0+a1α+?+a?α? with ai∈{0,1,2,3,4}. The set T of points with integer part 0 in this number system
932.
Bernardo Llano Juan José Montellano‐Ballesteros Eduardo Rivera‐Campo Ricardo Strausz 《Journal of Graph Theory》2008,57(4):344-352
An induced subgraph of a graph is called a derived subgraph of if contains no isolated vertices. An edge e of is said to be residual if e occurs in more than half of the derived subgraphs of . In this article, we prove that every simple graph with at least one edge contains a non‐residual edge. This was conjectured by El‐Zahar in 1997. © 2008 Wiley Periodicals, Inc. J Graph Theory 57: 344–352, 2008 相似文献
933.
A large set of Kirkman triple systems of order v, denoted by LKTS(v), is a collection , where every is a KTS(v) and all form a partition of all triples on X. In this article, we give a new construction for LKTS(6v + 3) via OLKTS(2v + 1) with a special property and obtain new results for LKTS, that is there exists an LKTS(3v) for , where p, q ≥ 0, r
i
, s
j
≥ 1, q
i
is a prime power and mod 12.
相似文献
934.
A tangency set of PG (d,q) is a set Q of points with the property that every point P of Q lies on a hyperplane that meets Q only in P. It is known that a tangency set of PG (3,q) has at most points with equality only if it is an ovoid. We show that a tangency set of PG (3,q) with , or points is contained in an ovoid. This implies the non‐existence of minimal blocking sets of size , , and of with respect to planes in PG (3,q), and implies the extendability of partial 1‐systems of size , , or to 1‐systems on the hyperbolic quadric . © 2007 Wiley Periodicals, Inc. J Combin Designs 16: 462–476, 2008 相似文献
935.
Alexander S. Kechris Todor Tsankov 《Proceedings of the American Mathematical Society》2008,136(2):687-697
In this paper, we study the connections between properties of the action of a countable group on a countable set and the ergodic theoretic properties of the corresponding generalized Bernoulli shift, i.e., the corresponding shift action of on , where is a measure space. In particular, we show that the action of on is amenable iff the shift has almost invariant sets.
936.
Gabriela?Hinojosa Alberto?Verjovsky 《Bulletin of the Brazilian Mathematical Society》2008,39(2):157-171
In this paper, we first define discrete, smooth actions on
, whose limit sets are Cantor sets wildly embedded in
(Antoine's necklaces). Secondly, we define Schottky groups on real projective spaces of odd dimensions,
. We lift these actions to (locally) projective actions on the sphere
and consider the quotient space of the domain of discontinuity by the group to obtain new examples of manifolds with real
projective structures.
*This work was partially supported by PROMEP (SEP).
**This work was partially supported by CONACyT (México), grant U1 55084, PAPIIT (UNAM) grant IN102108. 相似文献
937.
P-集合是把动态特性引入到有限普通集合X内,改进有限普通集合X得到的.层次P-集合是对普通P-集合的扩展,具有层次结构和链式结构.利用层次P-集合的性质,研究层次P-集合属性元素与规律,给出层次结构间属性元素的关系及度量,给出链式结构中属性元素的关系及度量,给出属性规律. 相似文献
938.
Computational Results for Regular Difference Systems of Sets Attaining or Being Close to the Levenshtein Bound 下载免费PDF全文
Difference systems of sets (DSSs) are combinatorial structures arising in connection with code synchronization that were introduced by Levenshtein in 1971, and are a generalization of cyclic difference sets. In this paper, we consider a collection of m‐subsets in a finite field of prime order to be a regular DSS for an integer m, and give a lower bound on the parameter ρ of the DSS using cyclotomic numbers. We show that when we choose ‐subsets from the multiplicative group of order e, the lower bound on ρ is independent of the choice of subsets. In addition, we present some computational results for DSSs with block sizes and , whose parameter ρ attains or comes close to the Levenshtein bound for . 相似文献
939.
The construction of group divisible designs (GDDs) is a basic problem in design theory. While there have been some methods concerning the constructions of uniform GDDs, the construction of nonuniform GDDs remains a challenging problem. In this paper, we present a new approach to the construction of nonuniform GDDs with group type and block size k. We make a progress by proposing a new construction, in which generalized difference sets, a truncating technique, and a difference method are combined to construct nonuniform GDDs. Moreover, we present a variation of this new construction by employing Rees' product constructions. We obtain several infinite families of nonuniform GDDs, as well as many examples whose block sizes are relatively large. 相似文献
940.
An elementary construction yields a new class of circulant (so‐called “Butson‐type”) generalized weighing matrices, which have order and weight n2, all of whose entries are nth roots of unity, for all positive integers , where . The idea is extended to a wider class of constructions giving various group‐developed generalized weighing matrices. 相似文献