Search results for "Combinatorics"
showing 10 items of 1770 documents
ARITHMETICAL QUESTIONS IN π-SEPARABLE GROUPS
2005
If G is a finite π-separable group, π a set of primes und X is a π-suhgroup of G, let vπ(G, X) be the number of Hall π-suhgroups of G containing X. If K is a subgroup of G containing X, we prove that vπ(K,X) divides vπ(G).
Closedness properties in ex-identification
2001
In this paper we investigate in which cases unions of identifiable classes are also necessarily identifiable. We consider identification in the limit with bounds on mindchanges and anomalies. Though not closed under the set union, these identification types still have features resembling closedness. For each of them we and n such that (1) if every union of n − 1 classes out of U1, ... , Un is identifiable, so is the union of all n classes; (2) there are classes U1, ... ,Un−1 such that every union of n−2 classes out of them is identifiable, while the union of n − 1 classes is not. We show that by finding these n we can distinguish which requirements put on the identifiability of unions of cl…
On bijections vs. unary functions
1996
A set of finite structures is in Binary NP if it can be characterized by existential second order formulas in which second order quantification is over relations of arity 2. In [DLS95] subclasses of Binary NP were considered, in which the second order quantifiers range only over certain classes of relations. It was shown that many of these subclasses coincide and that all of them can be ordered in a three-level linear hierarchy, the levels of which are represented by bijections, successor relations and unary functions respectively.
Basic Definitions and Facts
2001
Symbol is treated here as a primitive entity as point or line in geometry. Let Con = {f α : α < β} be a well-ordered set of symbols called a language type. β is an ordinal number. The elements of the above set are called connectives. To each connective f α a natural number α(α) ∈ w called the rank of f α or the arity of f α is assigned. The arity α(α) defines the number of arguments of f α . Thus we speak of nullary, unary, or binary connectives, etc. In the sequel Con is assumed to be fixed but arbitrary.
O(n 2 log n) Time On-Line Construction of Two-Dimensional Suffix Trees
2005
The two-dimensional suffix tree of an n × n square matrix A is a compacted trie that represents all square submatrices of Ai¾?[9]. For the off-line case, i.e., A is given in advance to the algorithm, it is known how to build it in optimal time, for any type of alphabet sizei¾?[9,15]. Motivated by applications in Image Compressioni¾?[18], Giancarlo and Guaianai¾?[12] considered the on-line version of the two-dimensional suffix tree and presented an On2log2n-time algorithm, which we refer to as GG. That algorithm is a non-trivial generalization of Ukkonen's on-line algorithm for standard suffix trees [19]. The main contribution in this paper is an Olog n factor improvement in the time complex…
Y-proper graded cocharacters and codimensions of upper triangular matrices of size 2, 3, 4
2012
Abstract Let F be a field of characteristic 0. We consider the upper triangular matrices with entries in F of size 2, 3 and 4 endowed with the grading induced by that of Vasilovsky. In this paper we give explicit computation for the multiplicities of the Y -proper graded cocharacters and codimensions of these algebras.
On the exponential growth of graded Capelli polynomials
2013
In a free superalgebra over a field of characteristic zero we consider the graded Capelli polynomials Cap M+1[Y,X] and Cap L+1[Z,X] alternating on M+1 even variables and L+1 odd variables, respectively. Here we compute the superexponent of the variety of superalgebras determinated by Cap M+1[Y,X] and Cap L+1[Z,X]. An essential tool in our computation is the generalized-six-square theorem proved in [3].
$n$-th relative nilpotency degree and relative $n$-isoclinism classes
2011
P. Hall introduced the notion of isoclinism between two groups more than 60 years ago. Successively, many authors have extended such a notion in different contexts. The present paper deals with the notion of relative n-isoclinism, given by N. S. Hekster in 1986, and with the notion of n-th relative nilpotency degree, recently introduced in literature.
A note on the exterior centralizer
2009
The notion of the exterior centralizer \({C_G^{^\wedge}(x)}\) of an element x of a group G is introduced in the present paper in order to improve some known results on the non-abelian tensor product of two groups. We study the structure of G by looking at that of \({C_G^{^\wedge}(x)}\) and we find some bounds for the Schur multiplier M(G) of G.
EXISTENCE OF THREE SOLUTIONS FOR A MIXED BOUNDARY VALUE PROBLEM WITH THE STURM-LIOUVILLE EQUATION
2012
Abstract. The aim of this paper is to establish the existence of threesolutions for a Sturm-Liouville mixed boundary value problem. The ap-proach is based on multiple critical points theorems. 1. IntroductionThe aim of this paper is to establish, under a suitable set of assumptions, theexistence of at least three solutions for the following Sturm-Liouville problemwith mixed boundary conditions(RS λ )ˆ−(pu ′ ) ′ +qu = λf(t,u) in I =]a,b[u(a) = u ′ (b) = 0,where λ is a positive parameter and p, q, f are regular functions. To be precise,if f : [a,b] × R→ Ris a L 2 -Carath´eodory function and p,q ∈ L ∞ ([a,b]) suchthatp 0 := essinf t∈[a,b] p(t) > 0, q 0 := essinf t∈[a,b] q(t) ≥ 0,then we prove …