All a b c d e f g h i j k l m n o p q r s t u v w x y z Other

Previous Page 8 Next

Displaying 141 – 160 of 399

Showing per page

Some additive applications of the isoperimetric approach

Yahya O. Hamidoune (2008)

Annales de l’institut Fourier

Let G be a group and let X be a finite subset. The isoperimetric method investigates the objective function | ( X B ) ∖ X | , defined on the subsets X with | X | ≥ k and | G ∖ ( X B ) | ≥ k , where X B is the product of X by B .In this paper we present all the basic facts about the isoperimetric method. We improve some of our previous results and obtain generalizations and short proofs for several known results. We also give some new applications.Some of the results obtained here will be used in coming papers to improve Kempermann structure...

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 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 ∩ Ann ( J ) ≠ ( 0 ) and J ∩ Ann ( I ) ≠ ( 0 ) . In this paper, the perfectness of SAG ( R ) for some classes of rings R is investigated.

Some crossing numbers of products of cycles

Marián Klešč (2005)

Discussiones Mathematicae Graph Theory

The exact values of crossing numbers of the Cartesian products of four special graphs of order five with cycles are given and, in addition, all known crossing numbers of Cartesian products of cycles with connected graphs on five vertices are summarized.

Currently displaying 141 – 160 of 399