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Displaying 321 – 340 of 430

Some algebraic properties of hypergraphs

Eric Emtander, Fatemeh Mohammadi, Somayeh Moradi (2011)

Czechoslovak Mathematical Journal

We consider Stanley-Reisner rings $k [x_{1}, ..., x_{n}] / I (ℋ)$ where $I (ℋ)$ is the edge ideal associated to some particular classes of hypergraphs. For instance, we consider hypergraphs that are natural generalizations of graphs that are lines and cycles, and for these we compute the Betti numbers. We also generalize some known results about chordal graphs and study a weak form of shellability.

Some applications of a theorem of Schur to graphs and to a class of endomorphisms

Chao, Chong-Yun (1967)

Portugaliae mathematica

Some applications of pq-groups in graph theory

Geoffrey Exoo (2004)

Discussiones Mathematicae Graph Theory

We describe some new applications of nonabelian pq-groups to construction problems in Graph Theory. The constructions include the smallest known trivalent graph of girth 17, the smallest known regular graphs of girth five for several degrees, along with four edge colorings of complete graphs that improve lower bounds on classical Ramsey numbers.

Some classes of perfect strongly annihilating-ideal graphs associated with commutative rings

Mitra Jalali, Abolfazl Tehranian, Reza Nikandish, Hamid Rasouli (2020)

Commentationes Mathematicae Universitatis Carolinae

Let $R$ be a commutative ring with identity and $A (R)$ be the set of ideals with nonzero annihilator. The strongly annihilating-ideal graph of $R$ is defined as the graph $SAG (R)$ with the vertex set $A {(R)}^{*} = A (R) ∖ {0}$ and two distinct vertices $I$ and $J$ are adjacent if and only if $I \cap Ann (J) \neq (0)$ and $J \cap Ann (I) \neq (0)$ . In this paper, the perfectness of $SAG (R)$ for some classes of rings $R$ is investigated.

Some globally determined classes of graphs

Ivica Bošnjak, Rozália Madarász (2018)

Czechoslovak Mathematical Journal

For a class of graphs we say that it is globally determined if any two nonisomorphic graphs from that class have nonisomorphic globals. We will prove that the class of so called CCB graphs and the class of finite forests are globally determined.

Some infinite p-groups.

Н. Гупта, С. Сидки (1983)

Algebra i Logika

Some non-normal Cayley digraphs of the generalized quaternion group of certain orders.

Dobson, Edward (2003)

The Electronic Journal of Combinatorics [electronic only]

Some properties of the zero divisor graph of a commutative ring

Khalida Nazzal, Manal Ghanem (2014)

Discussiones Mathematicae - General Algebra and Applications

Let Γ(R) be the zero divisor graph for a commutative ring with identity. The k-domination number and the 2-packing number of Γ(R), where R is an Artinian ring, are computed. k-dominating sets and 2-packing sets for the zero divisor graph of the ring of Gaussian integers modulo n, Γ(ℤₙ[i]), are constructed. The center, the median, the core, as well as the automorphism group of Γ(ℤₙ[i]) are determined. Perfect zero divisor graphs Γ(R) are investigated.

Some properties of unitary Cayley graphs.

Klotz, Walter, Sander, Torsten (2007)

The Electronic Journal of Combinatorics [electronic only]

Some results on the co-intersection graph of submodules of a module

Lotf Ali Mahdavi, Yahya Talebi (2018)

Commentationes Mathematicae Universitatis Carolinae

Let $R$ be a ring with identity and $M$ be a unitary left $R$ -module. The co-intersection graph of proper submodules of $M$ , denoted by $Ω (M)$ , is an undirected simple graph whose vertex set $V (Ω)$ is a set of all nontrivial submodules of $M$ and two distinct vertices $N$ and $K$ are adjacent if and only if $N + K \neq M$ . We study the connectivity, the core and the clique number of $Ω (M)$ . Also, we provide some conditions on the module $M$ , under which the clique number of $Ω (M)$ is infinite and $Ω (M)$ is a planar graph. Moreover, we give several...

Some results on the recognizability of the linear groups over the binary field

Mohammad Reza Darafsheh, Yaghoub Farjami, M. Khademi, Ali Reza Moghaddamfar (2005)

Commentationes Mathematicae Universitatis Carolinae

In this paper, we first find the set of orders of all elements in some special linear groups over the binary field. Then, we will prove the characterizability of the special linear group $PSL (13, 2)$ using only the set of its element orders.

Special m-hyperidentities in biregular leftmost graph varieties of type (2,0)

Apinant Anantpinitwatna, Tiang Poomsa-ard (2009)

Discussiones Mathematicae - General Algebra and Applications

Graph algebras establish a connection between directed graphs without multiple edges and special universal algebras of type (2,0). We say that a graph G satisfies a term equation s ≈ t if the corresponding graph algebra $\underset{̲}{A (G)}$ satisfies s ≈ t. A class of graph algebras V is called a graph variety if $V = M o d_{g} Σ$ where Σ is a subset of T(X) × T(X). A graph variety $V^{'} = M o d_{g} Σ^{'}$ is called a biregular leftmost graph variety if Σ’ is a set of biregular leftmost term equations. A term equation s ≈ t is called an identity in a variety...

Spectral deformations of automorphic functions over graphs of groups.

Isaac Efrat (1990)

Inventiones mathematicae

Stable rational cohomology of automorphism groups of free groups and the integral cohomology of moduli spaces of graphs.

Craig A. Jensen (2002)

Publicacions Matemàtiques

It is not known whether or not the stable rational cohomology groups H*(Aut(F∞);Q) always vanish (see Hatcher in [5] and Hatcher and Vogtmann in [7] where they pose the question and show that it does vanish in the first 6 dimensions). We show that either the rational cohomology does not vanish in certain dimensions, or the integral cohomology of a moduli space of pointed graphs does not stabilize in certain other dimensions. Similar results are stated for groups of outer automorphisms. This yields...

Strongly geodesically automatic groups are hyperbolic.

P. Papasoglu (1995)

Inventiones mathematicae

Structure of geodesics in the Cayley graph of infinite Coxeter groups

Ryszard Szwarc (2003)

Colloquium Mathematicae

Let (W,S) be a Coxeter system such that no two generators in S commute. Assume that the Cayley graph of (W,S) does not contain adjacent hexagons. Then for any two vertices x and y in the Cayley graph of W and any number k ≤ d = dist(x,y) there are at most two vertices z such that dist(x,z) = k and dist(z,y) = d - k. Allowing adjacent hexagons, but assuming that no three hexagons can be adjacent to each other, we show that the number of such intermediate vertices at a given distance from x and y...

Currently displaying 321 – 340 of 430

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Displaying 321 – 340 of 430

Some algebraic properties of hypergraphs

Some applications of a theorem of Schur to graphs and to a class of endomorphisms

Some applications of pq-groups in graph theory

Some classes of perfect strongly annihilating-ideal graphs associated with commutative rings

Some globally determined classes of graphs

Some infinite p-groups.

Some non-normal Cayley digraphs of the generalized quaternion group of certain orders.

Some properties of the zero divisor graph of a commutative ring

Some properties of unitary Cayley graphs.

Some results on the co-intersection graph of submodules of a module

Some results on the recognizability of the linear groups over the binary field

Special m-hyperidentities in biregular leftmost graph varieties of type (2,0)

Spectral deformations of automorphic functions over graphs of groups.

Stable rational cohomology of automorphism groups of free groups and the integral cohomology of moduli spaces of graphs.

Strongly geodesically automatic groups are hyperbolic.

Structure of geodesics in the Cayley graph of infinite Coxeter groups

Sur le problème des mots des quotients de groupes et produits libres

Sur les sections des hypergraphes et sur leurs automorphismes

Symmetric bowtie decompositions of the complete graph.

Symmetric groups and expanders.

Currently displaying 321 – 340 of 430