Journal of Linear and Topological Algebra
Year:2013 | Volume:2 | Issue:3|Papers Count:7

Let R be a 2-torsion free semiprime ring with extended centroid C, U the Utumi quotient ring of R and m; n>0 are xed integers. We show that if R admits derivation d such that b [[d (x); x]n; [y; d (y)]m]=0 for all x; y Î R where 0¹bÎR, then there exists a central idempotent element e of U such that eU is commutative ring and d induce a zero derivation on (1-e) U. We also obtain some related result in case R is a non-commutative Banach algebra and d continuous or spectrally bounded.

If we consider some special conditions, we can assume fundamental group of a topological space as a new topological space. In this paper, we will present a number of theorems in topological fundamental group related to semilocally simply connected property for a topological space.

One of the most practical routine tests for convergence of a positive series makes use of the ratio test. If this test fails, we can use Rabbe's test. When Rabbe's test fails the next sharper criteria which may sometimes be used is the Bertrand's test. If this test fails, we can use a generalization of Bertrand's test and such tests can be continued in finitely. For simplicity, we call ratio test, Rabbe's test, Bertrand's test as the Bertrand's test of order 0, 1 and 2, respectively. In this paper, we generalize Bertrand's test in order k for natural k>2.It is also shown that for any k, there exists a series such that the Bertrand's test of order fails, but such test of order k+1 is useful, furthermore we show that there exists a series such that for any k, Bertrand's test of order k fails. The only prerequisite for reading this article is a standard knowledge of advanced calculus.

In this paper we study the existence of commuting regular elements, verifying the notion left (right) commuting regular elements and its properties in the groupoid G (n). Also we show that G (n) contains commuting regular subsemigroup and give a necessary and sufficient condition for the groupoid G (n) to be commuting regular.

Let G be a finite group and p(G) be the set of all prime divisors of |G|. The prime graph of G is a simple graph G (G) with vertex set p(G) and two distinct vertices p and q in p(G) are adjacent by an edge if an only if G has an element of order pq. In this case, we write p ~ q. Let |G|=p a11. p a22…p akk, where p1<p2<…<pk are primes. For p Îp(G), let deg (p)=|{qÎp(G) |p ~ q}| be the degree of p in the graph G(G), we define D(G)=(deg (p1), deg (p2),…, deg (pk)) and call it the degree pattern of G. A group G is called k -fold OD-characterizable if there exist exactly k non-isomorphic groups S such that |G|=|S| and D(G)=D(S). Moreover, a 1-fold OD-characterizable group is simply called an OD-characterizable group. Let L=S4 (4) be the projective symplectic group in dimension 4 over a field with 4 elements. In this article, we classify groups with the same order and degree pattern as an almost simple group related to L. Since Aut (L)@Z4 hence almost simple groups related toL are L, L: 2 or L: 4. In fact, we prove that L, L: 2 and L: 4 are OD-characterizable.

In this paper, at first for a given set of real or complex numbers with nonnegative summation, we introduce some special conditions that with them there is no nonnegative tridiagonal matrix in which s is its spectrum. In continue we present some conditions for existence such nonnegative tridiagonal matrices.

A Class of new methods based on a septic non-polynomial spline function for the numerical solution one-dimensional Bratu's problem are presented. The local truncation errors and the methods of order 2th, 4th, 6th, 8th, 10th, and 12th, are obtained. The inverse of some band matrixes are obtained which are required in proving the convergence analysis of the presented method. Associated boundary formulas are developed. Convergence analysis of these methods is discussed. Numerical results are given to illustrate the efficiency of methods.