symmetric group

The minimum edge dominating energy of a graph $G$ is defined as the sum of the absolute values of eigenvalues of the minimum edge dominating matrix of $G$. In this paper, for some finite symmetric groups $\Gamma$ and subset $S$ of $\Gamma$, the minimum edge dominating energy of the Cayley graph of the group $\Gamma$, denoted by $Cay(\Gamma, S)$, is investigated.

For $n = 5, 6$ and $E = \End S_n$, the functions in the centralizer nearring $M_E(S_n) = \{f : S_n \to S_n \ |\ f(1) = (1) \ \hbox{and} \ f \circ s = s \circ f \ \hbox{for all}\ s \in E\}$ are determined.  The centers of these two nearrings are also described.  Results that can be used to determine the functions in $M_E(S_n)$ and their centers for $n \geq 7$ are also presented.

Let $S_n$ be the symmetric group on the set $[n]={1, 2, ldots, n}$. For $gin S_n$ let $fix(g)$ denote the number of fixed points of $g$. A subset $S$ of $S_n$ is called $t$-emph{transitive} if for any two $t$-tuples $(x_1,x_2,ldots,x_t)$ and $(y_1,y_2,ldots ,y_t)$ of distinct elements of $[n]$, there exists $gin S$ such that $x_{i}^g=y_{i}$ for any $1leq ileq t$ and additionally $S$ is called emph{sharply $t$-transitive} if for any given pair of $t$-tuples, exactly one element of $S$ carries the first to the second. In addition, a subset $S$ of $S_n$ is called $t$-intersecting if $fix(h^{-1}g)geq t$ for any two distinct permutations $h$ and $g$ of $S$. In this paper, we prove that there are only two sharply $(n-2)$-transitive subsets of $S_n$ and finally we establish some relations between sharply $k$-transitive subsets and $t$-intersecting subsets of $S_n$ where $k,tin mathbb{Z}$ and $0leq tleq kleq n$.

The commuting graph of a group is a graph with vertexes set of a subset of a group and two element are adjacent if they commute. The aim of this paper is to obtain the automorphism group of the commuting graph of a conjugacy class in the symmetric groups. The clique number, coloring number, independent number, and diameter of these graphs are also computed.

For a composition λ of n our aim is to obtain reduced forms for all the elements in the Kazhdan-Lusztig (right) cell containing w J(λ), the longest element of the standard parabolic subgroup of S n corresponding to λ. We investigate how far this is possible to achieve by looking at elements of the form w J(λ) d, where d is a prefix of an element of minimum length in a (W J(λ), B) double coset with the trivial intersection property, B being a parabolic subgroup of S n whose type is `dual'' to that of W J(λ).

Let $G$ be a finite group and $Gamma(G)$ the prime graph of $G$. Recently people have been using prime graphs to study simple groups. Naturally we pose a question: can we use prime graphs to study almost simple groups or non-simple groups? In this paper some results in this respect are obtained and as follows: $Gcong S_p$ if and only if $|G|=|S_p|$ and $Gamma(G)=Gamma(S_p)$, where $p$ is a prime.

Let gamma(Sn) be the minimum number of proper subgroups Hi, i = 1,...,ell, of the symmetric group Sn such that each element in Sn lies in some conjugate of one of the Hi. In this paper we conjecture that gamma(Sn) =(n/2)(1-1/p_1) (1-1/p_2) + 2, where p1, p2 are the two smallest primes in the factorization of n and n is neither a prime power nor a product of two primes. Support for the conjecture is given by a previous result for the case where n has at most two distinct prime divisors. We give further evidence by confirming the conjecture for certain integers of the form n = 15q, for an infinite set of primes q, and by reporting on a Magma computation. We make a similar conjecture for gamma(An), when n is even, and provide a similar amount of evidence.

The non-commuting graph $nabla(G)$ of a non-abelian group $G$ is defined as follows: its vertex set is $G-Z(G)$ and two distinct vertices $x$ and $y$ are joined by an edge if and only if the commutator of $x$ and $y$ is not the identity. In this paper we ''ll prove that if $G$ is a finite group with $nabla(G)congnabla(BS_{n})$, then $G cong BS_{n}$, where $BS_{n}$ is the symmetric group of degree $n$, where $n$ is a natural number.