Search

It is shown that an approach earlier used by the author for classification of closed simply connected 6-manifolds (reduction to the problem of calculating certain bordism groups) can also be applied for easily obtaining the results by Barden (1965) on classification of closed simply connected 5-manifolds. Bibliography: 11 titles.

Let A be a partition of the segment [0, 1] into a countable number of disjoint subsets of positive measure, let t∈L1(0,1), let Nt be the smallest rearrangement-invariant order ideal vector lattice in L1(0,1), containing t. In the paper one investigates the properties of the image E(Nt¦A) of the averaging operator with respect to A. In particular, one elucidates under what conditions there exists a function g, g∈L1(0,1), such that E(Nt¦A)⊂Ng. One formulates a generalization of the known Hardy-Littlewood inequality, namely Theorem E(t∣A)≺QE(t*∣A*), where ≺ is the Hardy-Littlewood preorder, t* and A* are the decreasing rearrangements of the function ¦t¦ and (in a special sense) of the partition A, while Q is an absolute constant, 1⩽Q⩽25. One formulates the problem of the smallest value of Q.

Let λK m,n be a complete bipartite multigraph with two partite sets having m and n vertices, respectively. A K p,q -factorization of λK m,n is a set of edge-disjoint K p,q -factors of λK m,n which partition the set of edges of λK m,n . When p = 1 and q is a prime number, Wang, in his paper [On K 1,q -factorization of complete bipartite graph, Discrete Math., 126: (1994), 359-364], investigated the K 1,q -factorization of K m,n and gave a sufficient condition for such a factorization to exist. In papers [K 1,k -factorization of complete bipartite graphs, Discrete Math., 259: 301-306 (2002),; K p,q -factorization of complete bipartite graphs, Sci. China Ser. A-Math., 47: (2004), 473-479], Du and Wang extended Wang’s result to the case that p and q are any positive integers. In this paper, we give a sufficient condition for λK m,n to have a K p,q -factorization. As a special case, it is shown that the necessary condition for the K p,q -factorization of λK m,n is always sufficient when p : q = k : (k + 1) for any positive integer k.

The present paper is devoted to graph-links with many components and consists of two parts. In the first part of the paper we classify vertices of a labeled graph according to the component they belong to. Using this classification, we construct an invariant of graph-links. This invariant shows that the labeled second Bouchet graph generates a nonrealizable graph-link. In the second part of the work we introduce the notion of an oriented graph-link. We define a writhe number for the oriented graph-link and we get an invariant of oriented graph-links, the Jones polynomial, by normalizing the Kauffman bracket with the writhe number.

Let $X,X_1,\ldots,X_n$ be independent identically distributed random variables. The paper deals with the question about the behavior of the concentration function of the random variable $\sum\limits_{k=1}^{n}X_k a_k$ according to the arithmetic structure of vectors $a_k$. Recently, the interest to this question has increased significantly due to the study of distributions of eigenvalues of random matrices. In this paper we formulate and prove multidimensional generalizations of the results Eliseeva and Zaitsev (2012). They are also the refinements of the results of Friedland and Sodin (2007) and Rudelson and Vershynin (2009)., Comment: 13 pages

This paper discusses the asymptotic behaviors of the longest run on a countable state Markov chain. Let \(\left\{ {X_a } \right\}_{a \in Z_ + }\) be a stationary strongly ergodic reversible Markov chain on countablestate space S = {1, 2, ...}. Let T ⊂ S be an arbitrary finite subset of S. Denote by L n the length of the longest run of consecutive i’s for i ∈ T, that occurs in the sequence X 1, ..., X n . In this paper, we obtain a limit law and a week version of an Erdos-Renyi type law for L n . A large deviation result of L n is also discussed.

The Q-index of a simple graph is the largest eigenvalue of its signless Laplacian, or Q-matrix. In our previous paper [1] we gave three lower and three upper bounds for the Q-index of nested split graphs, also known as threshold graphs. In this paper, we give another two upper bounds, which are expressed as solutions of cubic equations (in contrast to quadratics from [1]). Some computational results are also included.

In this paper, we present a large-update interior-point algorithm for convex quadratic semi-definite optimization based on a new kernel function. The proposed function is strongly convex. It is not self-regular function and also the usual logarithmic function. The goal of this paper is to investigate such a kernel function and show that the algorithm has favorable complexity bound in terms of the elegant analytic properties of the kernel function. The complexity bound is shown to be \(O\left( {\sqrt n \left( {\log n} \right)^2 \log \frac{n} {\varepsilon }} \right)\). This bound is better than that by the classical primal-dual interior-point methods based on logarithmic barrier function and recent kernel functions introduced by some authors in optimization fields. Some computational results have been provided.

This paper deals with an extremal problem concerning hypergraph colorings. Let k be an integer. The problem is to find the value mk(n) equal to the minimum number of edges in an n-uniform hypergraph not admitting two-colorings of the vertex set such that every edge of the hypergraph contains k vertices of each color. In this paper, we obtain the exact values of m2(5) and m2(4), and the upper bounds for m3(7) and m4(9).

In this paper, we consider structured automata without output signals whose state sets are endowed with an algebraic structure of hypergraphs. The main result of the paper is a theorem where we obtain necessary and sufficient conditions for the possibility of defining on the state set of some automaton A a structure of a hypergraph H such that the automaton A will be the universal hypergraphic automaton.

Let $$f : {\mathbb{R}} \longrightarrow {\mathbb{R}}$$ denote the function given by $$f(t) = \sum \limits^{\infty}_{n=0} a_{n}t^{n}, t \in {\mathbb{R}}$$ , where $$a_n \geq 0, n \in {\mathbb{N}}$$ . Let K be a closed convex cone in a real Banach space and $$H : K \longrightarrow cc(K)$$ a linear and continuous set-valued function with nonempty, convex and compact values in K. The set-valued function $$F^t(x) := \sum \limits_{n=0}^{\infty} a_{n}t^{n}H^{n}(x), x \in K$$ is linear and continuous for all $$t \geq 0$$ and $$F^{t} \circ F^{s}(x) \subseteq \sum \limits_{n=0}^{\infty} c_{n}H^{n} (x), x \in K$$ where $$c_{n} = \sum \limits_{k=0}^{n} a_{k} a_{n-k}{{t^{k}}s^{n-k}}, t, s \geq 0$$ . The paper generalizes papers of J. Plewnia and M. Piszczek where f is an exponential and a cosine function respectively.

In this paper we pursue and deep the study of ring extensions \({R \subset S}\) such that R is a maximal non-valuation subring of S [Ben Nasr and Jarboui in Houston J Math, 2009 (in press)]. It is proved in Ben Nasr and Jarboui [Houston J Math, 2009 (in press), Theorem 3.2] that if R is integrally closed with finite Krull dimension, then R is a maximal non-valuation subring of qf (R) iff R is not local and |[R, qf (R)]| = dim(R) + 3. This result encourages us to pose the following question: Let n be a nonzero positive integer greater than 2 and let R be a finite-dimensional domain such that |[R, qf (R)]| = dim(R) + n, does there exists an overring S of R such that R is a maximal non-valuation subring of S? This paper deals mostly with this question. We solve this question in case R is integrally closed.

This paper is a follow-up to a previous paper where the logical characterization of n-ary synchronous relations due to Eilenbeig, Elgot, and Shepherdson was investigated in the case where the alphabet has infinitely many letters. Here we show that modifying one of the predicates leads to a completely different picture for infinite alphabets, though it does not change the expressive power for finite alphabets. Indeed, roughly speaking, being able to express the fact that two words end with the same symbol leads to an undecidable theory, already for the Σ2 fragment. Finally, we show that the existential fragment is decidable. Bibliography: 19 titles.

A partial order on the set of the prime knots can be defined by the existence of a surjective homomorphism between knot groups. In the previous paper, we determined the partial order in the knot table. In this paper, we prove that 31 and 41 are minimal elements. Further, we study which surjection a pair of a periodic knot and its quotient knot induces, and which surjection a degree one map can induce.

Let A be a class of Abelian groups, A ∈ A, and End(A) be the additive endomorphism group of the group A. The group A is said to be defined by its endomorphism group in the class {ie208-01} if for every group B ∈ B such that End(B) ≅ End(A) the isomorphism B ≅ A holds. The paper considers the problem of definability of a periodic Abelian group A such that End-End(A) ≅ End(A). The classes of periodical Abelian groups, of divisible Abelian groups, of reduced Abelian groups, of nonreduced Abelian groups, and of all Abelian groups are investigated in this paper.

Plesnik in 1972 proved that an (m − 1)-edge connected m-regular graph of even order has a 1-factor containing any given edge and has another 1-factor excluding any given m − 1 edges. Alder et al. in 1999 showed that if G is a regular (2n + 1)-edge-connected bipartite graph, then G has a 1-factor containing any given edge and excluding any given matching of size n. In this paper we obtain some sufficient conditions related to the edge-connectivity for an n-regular graph to have a k-factor containing a set of edges and (or) excluding a set of edges, where 1 ≤ k ≤ n/2. In particular, we generalize Plesnik’s result and the results obtained by Liu et al. in 1998, and improve Katerinis’ result obtained 1993. Furthermore, we show that the results in this paper are the best possible.

It is well known that there are no nonzero linear derivations on complex commutative semisimple Banach algebras. In this paper we prove the following extension of this result. Let A be a complex semisimple Banach algebra and let D : A → A be a linear mapping satisfying the relation D(x 2) = 2xD(x) for all x ∈ R. In this case D = 0. Throughout, R will represent an associative ring with center Z(R). A ring R is n-torsion free, where n > 1 is an integer, if nx = 0, x ∈ R implies x = 0. As usual the commutator xy − yx will be denoted by [x, y]. We shall use the commutator identities [xy, z] = [x, z] y + x [y, z] and [x, yz] = [x, y] z + y [x, z] for all x, y, z ∈ R. Recall that a ring R is prime if for a, b ∈ R, aRb = (0) implies that either a = 0 or b = 0, and is semiprime in case aRa = (0) implies that a = 0. An additive mapping D is called a derivation if D(xy) = D(x)y + xD(y) holds for all pairs x, y ∈ R, and is called a Jordan derivation in case D(x 2) = D(x)x + xD(x) is fulfilled for all x ∈ R. Obviously, any derivation is a Jordan derivation. The converse is in general not true. Herstein ([8]) has proved that any Jordan derivation on a 2-torsion free prime ring is a derivation (see also [1]). Cusack ([5]) has generalized Herstein’s result to 2-torsion free semiprime rings (see [2] for an alternative proof). An additive mapping D : R → R is called a left derivation if D(xy) = yD(x) + xD(y) holds for all pairs x, y ∈ R and is called a left Jordan derivation (or Jordan left derivation) in case D(x 2) = 2xD(x) is fulfilled for all x ∈ R. In this paper by a Banach algebra we mean a Banach algebra over the complex field.

This paper compares sequences of independent, mean zero random variables in a rearrangement-invariant space X on [0, 1] with sequences of disjoint copies of individual terms in the corresponding rearrangement-invariant space Z X 2 on [0, ∞). The principal results of the paper show that these sequences are equivalent in X and Z X 2 , respectively, if and only if X possesses the (so-called) Kruglov property. We also apply our technique to complement well-known results concerning the isomorphism between rearrangement-invariant spaces on [0, 1] and [0, ∞). Bibliography: 20 titles.

A new method, which enables us to compute rather efficiently the Galois group of a polynomial over ℚ or over ℤ, is presented. Reductions of this polynomial with respect to different prime modules are studied, and the information obtained is used for the calculation of the Galois group of the initial polynomial. This method uses an original modification of the Chebotarev density theorem, and it is in essence a probabilistic method. The irreducibility of the polynomial under consideration is not assumed. The appendix to this paper contains tables, which enable us to find the Galois group of polynomials of degree less than or equal to 10 as a subgroup of the symmetric group. Here the final part of the paper is published. The first part is contained in a previous issue (see Vol. 134, No. 6 (2006)). Bibliography: 10 titles.

An excellent introduction to the topic of poset matroids is due to M. Barnabei, G. Nicoletti and L. Pezzoli. On the basis of their work, we have obtained the global rank axioms for poset matroids. In this paper, we study the special integral function f and obtain a new class of poset matroids from the old ones, and then we generalize this result according to the properties of f. Almost all of these results can be regarded as the application of global rank axioms for poset matroids. The main results in our paper have, indeed, investigated the restriction of the basis of the poset matroid, and we give them the corresponding geometric interpretation.

A. A. Tuganbaev UDC 512.55All rings are assumed to be associative and to have a nonzero identity element. Let A be a ring,and let M be a rightA-module. A proper ideal P ofthe ringA is said to be right primitive if P is theannihilator ofa simple rightA-module (i.e., ifthere exists a maximal right idealB ofthe ringA suchthat P is the largest ideal of A contained in B). Consequently, every maximal ideal is a right and leftprimitive ideal. A submodule N ofthe moduleM is said to be primitively pure (resp. maximally pure)ifNP = NMP for every right primitive (resp. maximal) idealP ofthe ringA. A module M is said tobe primitively divisible (resp. maximally divisible)ifM = MP for every right primitive (resp. maximal)ideal P ofthe ringA.AringA is called a right max ring ifevery nonzero rightA-module has a maximalsubmodule. Maximally pure submodules and maximally divisible modules are studied in [3,4,6,7]. In [5],right max rings with polynomial identity are described. In [10], right quasi-invariant right max rings aredescribed.The main results ofthis paper are Theorems 1 and 2.Theorem1. Let A be either a P.I. ring or a right quasi-invariant ring. Then the following conditionsare equivalent.(1) A is a regular ring.(2) All submodules of any right A-module are primitively pure.(3) All submodules of any right A-module are maximally pure.(4) All principal right ideals of the ring A are primitively pure.(5) All principal right ideals of the ring A are maximally pure.Remark1. Let A be a simple ring. It is obvious that all submodules ofanyA-module M are maximallypure and primitively pure in M. Since the ring A is not necessarily regular, Theorem 1 does not hold forarbitrary rings.Theorem2. For a P.I. ring A,the following conditions are equivalent.(1) All prime ideals of the ring A are maximal ideals,andJ(A) is a right or left t-nilpotent ideal.(2) There do not exist nonzero primitively divisible right A-modules.(3) There do not exist nonzero primitively divisible left A-modules.(4) There do not exist nonzero maximally divisible right A-modules.(5) There do not exist nonzero maximally divisible left A-modules.(6) A is a right max ring.(7) A is a left max ring.The paper also contains some other assertions on primitively (resp. maximally) pure submodulesand primitively (resp. maximally) divisible modules.The proofs of Theorems 1 and 2 are decomposed into a series of lemmas. We present the necessarynotation and definitions. For a module M,theJacobson radical of M is denoted by J(M). For a moduleM and its subset X,wedenotebyr(X) the annihilator of X. For a module M, a submodule N ofM is said to be essential if NX = 0 for every nonzero submoduleX ofthe moduleM.AringA issaid to be regular if a ∈ aAa for each element a ∈ A.AringA is said to be right quasi-invariant if

The Paul Erdős and Andras Gyarfas conjecture states that every graph of minimum degree at least 3 contains a simple cycle whose length is a power of two. In this paper, we prove that the conjecture holds for Cayley graphs on generalized quaternion groups, dihedral groups, semidihedral groups and groups of order \(p^3\).

Let G = (V,E) be a simple graph. A function f: E → {+1,−1} is called a signed cycle domination function (SCDF) of G if Ʃ e∈E(C) f(e) ≥ 1 for every induced cycle C of G. The signed cycle domination number of G is defined as γ′sc(G) = min{Ʃ e∈E f(e)| f is an SCDF of G}. This paper will characterize all maximal planar graphs G with order n ≥ 6 and γ′sc(G) = n.

Let G be a finite group and σ = {σ i |i∈I} be a partition of the set of all primes P. A set H of subgroups of G is said to be a complete Hall σ-set of G if every non-identity member of H is a Hall σ i -subgroup of G and H contains exactly one Hall σ i -subgroup of G for every σ i ∈ σ(G). A subgroup H is said to be σ-permutable if G possesses a complete Hall σ-set H such that HA x = A x H for all A ∈ H and all x ∈ G. Let H be a subgroup of G. Then we say that: (1) H is σ-embedded in G if there exists a σ-permutable subgroup T of G such that HT = H σG and H ∩ T ≤ H σG , where H σG is the subgroup of H generated by all those subgroups of H which are σ-permutable in G, and H σG is the σ-permutable closure of H, that is, the intersection of all σ-permutable subgroups of G containing H. (2) H is σ-n-embedded in G if there exists a normal subgroup T of G such that HT = H G and H ∩ T ≤ H σG . In this paper, we study the properties of the new embedding subgroups and use them to determine the structure of finite groups.

Let G be a graph and let its maximum degree and maximum average degree be denoted by Δ(G) and mad(G), respectively. A neighbor sum distinguishing k-edge colorings of graph G is a proper k-edge coloring of graph G such that, for any edge uv ∈ E(G), the sum of colors assigned on incident edges of u is different from the sum of colors assigned on incident edges of v. The smallest value of k in such a coloring of G is denoted by χ′∑(G). Flandrin et al. proposed the following conjecture that χ′∑ (G) ≤ Δ(G) + 2 for any connected graph with at least 3 vertices and G ≠ C5. In this paper, we prove that the conjecture holds for a normal graph with mad(G) < $$\tfrac{{37}} {{12}}$$ and Δ(G) ≥ 7.

In this paper we study trigonometric series with general monotone coefficients, i.e., satisfying $$\begin{aligned} \sum \limits _{k=n}^{2n} |a_k - a_{k+1}| \le C \sum \limits _{k=[{n}/{\gamma }]}^{[\gamma n]} \frac{|a_k|}{k}, \quad n\in \mathbb {N}, \end{aligned}$$ for some $$C \ge 1$$ and $$\gamma >1$$ . We first prove the Lebesgue-type inequalities for such series $$\begin{aligned} n|a_n|\le C \omega (f,1/n). \end{aligned}$$ Moreover, we obtain necessary and sufficient conditions for the sum of such series to belong to the generalized Lipschitz, Nikolskii, and Zygmund spaces. We also prove similar results for trigonometric series with weak monotone coefficients, i.e., satisfying $$\begin{aligned} |a_n | \le C \sum \limits _{k=[{n}/{\gamma }]}^{\infty } \frac{|a_k|}{k}, \quad n\in \mathbb {N}, \end{aligned}$$ for some $$C \ge 1$$ and $$\gamma >1$$ . Sharpness of the obtained results is given. Finally, we study the asymptotic results of Salem–Hardy type.

Let A be an integral domain, $$S\subseteq A$$ be a multiplicative set and M a w-module as an A-module. In this paper we investigate S-SM-modules. We give an S-version of the result of Wang and McCasland (Commun Algebra 25:1285–1306, 1997) in the case where S is countable. We prove that M is an S-SM-module if and only if every increasing sequence of w-submodules of M is S-stationary if and only if every increasing sequence of S-w-finite w-submodules of M is S-stationary if and only if every increasing sequence of w-finite type submodules of M is S-stationary.

This paper delves into the number of partitions of positive integers n into powers of 2 in which exactly m powers of 2 are used an odd number of times. The study of these numbers is motivated by their connections with the f-vectors of the binary partition polytopes.

Let S = (a 1, …, a m ; b 1, …, b n ), where a 1, …, a m and b 1, …, b n are two nonincreasing sequences of nonnegative integers. The pair S = (a 1, …, a m ; b 1, …, b n ) is said to be a bigraphic pair if there is a simple bipartite graph G = (X ∪ Y, E) such that a 1, …, a m and b 1, …, b n are the degrees of the vertices in X and Y, respectively. Let Z 3 be the cyclic group of order 3. Define σ(Z 3, m, n) to be the minimum integer k such that every bigraphic pair S = (a 1, …, a m ; b 1, …, b n ) with a m , b n ≥ 2 and σ(S) = a 1 + ⋯ + a m ≥ k has a Z 3-connected realization. For n = m, Yin [Discrete Math., 339, 2018—2026 (2016)] recently determined the values of σ(Z 3, m, m) for m ≥ 4. In this paper, we completely determine the values of σ(Z 3, m, n) for m ≥ n ≥ 4.

Let R be a commutative semiring with nonzero identity and H be a multiplicative-prime subset of R. The generalized total graph of a commutative semiring R is the (undirected) graph \(GT_{H}(R)\) whose vertices are all elements of R and two distinct vertices x and y are adjacent if and only if \(x+y\in H\). In this paper, we investigate the structure of \(GT_{H}(R)\) and we also study the two (induced) subgraphs \(GT_{H}(H)\) and \(GT_{H}(R{\setminus } H)\) with vertex-sets H and \(R{\setminus } H\).

A proper edge-k-coloring of a graph G is a mapping from E(G) to {1, 2,..., k} such that no two adjacent edges receive the same color. A proper edge-k-coloring of G is called neighbor sum distinguishing if for each edge uv ∈ E(G), the sum of colors taken on the edges incident to u is different fromthe sumof colors taken on the edges incident to v. Let χ′Σ(G) denote the smallest value k in such a coloring of G. This parameter makes sense for graphs containing no isolated edges (we call such graphs normal). The maximum average degree mad(G) of G is the maximum of the average degrees of its non-empty subgraphs. In this paper, we prove that if G is a normal subcubic graph with mad(G) < 5/2, then χ′Σ(G) ≤ 5. We also prove that if G is a normal subcubic graph with at least two 2-vertices, 6 colors are enough for a neighbor sum distinguishing edge coloring of G, which holds for the list version as well.

Let S be a subset of a finite abelian group G. The Cayley sum graph Cay+(G, S) of G with respect to S is a graph whose vertex set is G and two vertices g and h are joined by an edge if and only if g + h ∈ S. We call a finite abelian group G a Cayley sum integral group if for every subset S of G, Cay+(G, S) is integral i.e., all eigenvalues of its adjacency matrix are integers. In this paper, we prove that all Cayley sum integral groups are represented by Z3 and Zn2n, n ≥ 1, where Zk is the group of integers modulo k. Also, we classify simple connected cubic integral Cayley sum graphs.

Let G be a finite group and NA(G) denote the number of conjugacy classes of all nonabelian subgroups of non-prime-power order of G. The Symbol π(G) denote the set of the prime divisors of |G|. In this paper we establish lower bounds on NA(G). In fact, we show that if G is a finite solvable group, then NA(G) = 0 or NA(G) ≥ 2|π(G)|−2, and if G is non-solvable, then NA(G) ≥ |π(G)| + 1. Both lower bounds are best possible.

In the paper, the authors present some properties, including convexity, complete monotonicity, product inequalities, and determinantal inequalities, of the large Schroder numbers and find three relations between the Schroder numbers and central Delannoy numbers. Moreover, the authors sketch generalizing the Schroder numbers and central Delannoy numbers and their generating functions.

Assume G is a finite group and H a subgroup of G. If there exists a subgroup K of G such that G = HK and H ∩ K = 1, then K is said to be a complement to H in G. A finite p-group G is called an NC-group if all its proper normal subgroups not contained in Φ(G) have complements. In this paper, some properties of NC-groups are investigated and some classes of NC-groups are classified.

Let R be a commutative ring with identity and let Z(R, k) be the set of all k-zero-divisors in R and $$k>2$$ an integer. The k-zero-divisor hypergraph of R, denoted by $$\mathcal {H}_k(R)$$ , is a hypergraph with vertex set Z(R, k), and for distinct elements $$x_1,x_2,\ldots ,x_k$$ in Z(R, k), the set $$\{x_1,x_2, \ldots , x_k\}$$ is an edge of $$\mathcal {H}_k(R)$$ if and only if $$\prod \limits _{i=1}^kx_i =0$$ and the product of any $$(k-1)$$ elements of $$\{x_1,x_2,\ldots ,x_k\}$$ is nonzero. In this paper, we characterize all finite commutative non-local rings R with identity whose $$\mathcal {H}_3(R)$$ has crosscap one.

In this paper, we investigate the intersection numbers of nearly Kirkman triple systems. JN[v] is the set of all integers k such that there is a pair of NKTS(v)s with a common uncovered collection of 2-subset intersecting in k triples. It has been established that \({J_N}\left[ v \right] = \left\{ {0,1,...,\frac{{v\left( {v - 2} \right)}}{6} - 6,\frac{{v\left( {v - 2} \right)}}{6} - 4,\frac{{v\left( {v - 2} \right)}}{6}} \right\}\) for any integers v = 0 (mod 6) and v ≥ 66. For v ≤ 60, there are 8 cases left undecided.

Let R be a commutative ring with nonzero identity. We denote by AG(R) the annihilator graph of R, whose vertex set consists of the set of nonzero zero-divisors of R, and two distint vertices x and y are adjacent if and only if \(\mathrm {ann}(x) \cup \mathrm {ann}(y) \ne \mathrm {ann}(xy)\), where for \(t\in R\), we set \(ann(t) := \lbrace r\in R\ \vert \ rt=0\rbrace \). In this paper, we define the annihiator-ideal graph of R, which is denoted by \(A_{I}(R)\), as an undirected graph with vertex set \(A^*(R)\), and two distinct vertices I and J are adjacent if and only if \(\mathrm {ann}(I) \cup \mathrm {ann}(J) \ne \mathrm {ann}(IJ)\). We study some basic properties of \(A_{I}(R)\) such as connectivity, diameter and girth. Also we investigate the situations under which the graphs AG(R) and \(A_{I}(R)\) are coincide. Moreover, we examin the planarity of the graph \(A_{I}(R)\).

Let X denote a compact metric space with distance d and F : X × ℝ → X or Ft : X → X denote a C0-flow. From the point of view of ergodic theory, all important dynamical behaviors take place on a full measure set. The aim of this paper is to introduce the notion of Banach upper density recurrent points and to show that the closure of the set of all Banach upper density recurrent points equals the measure center or the minimal center of attraction for a C0-flow. Moreover, we give an example to show that the set of quasi-weakly almost periodic points can be included properly in the set of Banach upper density recurrent points, and point out that the set of Banach upper density recurrent points can be included properly in the set of recurrent points.

In this paper, we introduce a novel polynomial-time algorithm to compute graph invariants based on the idea of a modified random walk on graphs. Though not proved to be a full graph invariant yet, our method gives the right answer for the graph instances other well-known methods could not compute (such as special Furer gadgets and point-line incidence graphs of finite projective planes of higher degrees).

In this paper, we study the class S of skew Motzkin paths, i.e., of those lattice paths that are in the first quadrat, which begin at the origin, end on the x-axis, consist of up steps U = (1, 1), down steps D = (1,−1), horizontal steps H = (1, 0), and left steps L = (−1,−1), and such that up steps never overlap with left steps. Let S n be the set of all skew Motzkin paths of length n and let s n = |S n |. Firstly we derive a counting formula, a recurrence and a convolution formula for sequence {s n } n ≥0. Then we present several involutions on S n and consider the number of their fixed points. Finally we consider the enumeration of some statistics on S n .

The minimality theorem states, in particular, that on cohomology H(A) of a dg algebra there exists sequence of operations mi : H(A)⊗i → H(A), i = 2, 3, . . . , which form a minimal A ∞ -algebra (H(A), {m i }). This structure defines on the bar construction BH(A) a correct differential dm so that the bar constructions (BH(A), d m ) and BA have isomorphic homology modules. It is known that if A is equipped additionally with a structure of homotopy Gerstenhaber algebra, then on BA there is a multiplication which turns it into a dg bialgebra. In this paper, we construct algebraic operations Ep,q : H(A) ⊗p ⊗H(A) ⊗q → H(A), p, q = 0, 1, 2, . . ., which turn (H(A), {m i }, {E p,q }) into a B ∞ -algebra. These operations determine on BH(A) correct multiplication, so that (BH(A), d m ) and BA have isomorphic homology algebras.

In this paper, the problem of construction of exponentially many minimum genus embeddings of complete graphs in surfaces are studied. There are three approaches to solve this problem. The first approach is to construct exponentially many graphs by the theory of graceful labeling of paths; the second approach is to find a current assignment of the current graph by the theory of current graph; the third approach is to find exponentially many embedding (or rotation) schemes of complete graph by finding exponentially many distinct maximum genus embeddings of the current graph. According to this three approaches, we can construct exponentially many minimum genus embeddings of complete graph K 12s+8 in orientable surfaces, which show that there are at least $$\frac{10}{3} \times (\frac{200}{9})^s$$ distinct minimum genus embeddings for K 12s+8 in orientable surfaces. We have also proved that K 12s+8 has at least $$\frac{10}{3} \times (\frac{200}{9})^s$$ distinct minimum genus embeddings in non-orientable surfaces.

An edge-coloring of a graph G is an assignment of colors to all the edges of G. A gc-coloring of a graph G is an edge-coloring of G such that each color appears at each vertex at least g(v) times. The maximum integer k such that G has a gc-coloring with k colors is called the gc-chromatic index of G and denoted by \(\chi\prime_{g_{c}}\) (G). In this paper, we extend a result on edge-covering coloring of Zhang and Liu in 2011, and give a new sufficient condition for a simple graph G to satisfy \(\chi\prime_{g_{c}}\) (G) = δg(G), where \(\delta_{g}\left(G\right) = min_{v\epsilon V (G)}\left\{\lfloor\frac{d\left(v\right)}{g\left(v\right)}\rfloor\right\}\).

Let G be a finite group, Irr1(G) be the set of nonlinear irreducible characters of G and cd1(G) the set of degrees of the characters in Irr1(G). A group G is said to be a D2-group if |cd1(G)| = |Irr1(G)| − 2. In this paper, we give a complete classification of solvable D2-groups.

We construct a polyanalytic extension of analytic (Poisson) wavelet frames, leading to a new system of wavelet superframes. Superframes have been introduced in signal analysis as a tool for the multiplexing of signals—encoding several signals as a single one with the purpose of sharing a communication channel. In this paper, a new system of vector-valued wavelets is constructed by selecting as elements of the analyzing vector the first n elements from an explicit orthogonal basis of the space of admissible functions depending on a parameter \(\alpha \). We show that if the resulting discrete affine system indexed by the set \(\Gamma (a,b)=\{a^{m}bk,a^{m}\}_{k,m\in \mathbb {Z} }\) is a wavelet superframe, then the estimate $$\begin{aligned} b\log a

A book embedding of a graph G consists of placing the vertices of G on a spine and assigning edges of the graph to pages so that edges in the same page do not cross each other. The page number is a measure of the quality of a book embedding which is the minimum number of pages in which the graph G can be embedded. In this paper, the authors discuss the embedding of the generalized Petersen graph and determine that the page number of the generalized Petersen graph is three in some situations, which is best possible.

In this paper, we give new upper bounds for the chromatic numbers for integer lattices and some rational spaces and other lattices. In particular, we have proved that for any concrete integer number d, the chromatic number of ℤn with critical distance \( \sqrt{2d} \) has a polynomial growth in n with exponent less than or equal to d (sometimes this estimate is sharp). The same statement is true not only in the Euclidean norm, but also in any lp norm. Moreover, we have given concrete estimates for some small dimensions as well as upper bounds for the chromatic number of ℚpn, where by ℚp we mean the ring of all rational numbers having denominators not divisible by some prime numbers.

Many invariants of knots rely upon smoothing the knot at its crossings. To compute them, it is necessary to know how to count the number of connected components the knot diagram is broken into after the smoothing. In this paper, it is shown how to use a modification of a theorem of Zulli together with a modification of the spectral theory of graphs to approach such problems systematically. We give an application to counting subdiagrams of pretzel knots which have one component after oriented and unoriented smoothings.

The paper presents estimates of small deviation probabilities of the sum $$ {\displaystyle \sum_{j\ge 1}{\leftthreetimes}_j{X}_j} $$ , where {⋋j} are positive numbers and {Xj} are i.i.d. positive random variables satisfying weak restrictions at zero and infinity. Bibliography: 16 titles.