Revistas académicas de la Universidad Católica del Norte
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On commutativity of right S-unital rings with some polynomial constraints
No full textWe study the commutativity of certain class of rings, namely rings with unity 1 and right s-unital under each of the following properties [yxm - xn f (y) xP , x]= 0, [yxm + xn f (y) xP, x] = 0, where f (t) is a polynomial in t2Z [t] varying with pair of ring elements x, y and m, n, p are fixed non-negative integers. Moreover, the results have been extended to the case when m and n depend on the choice of x and y and the ring satisfies the Chacron's Theorem
On the arithmetic sum of middle-cantor sets
No full textIn this article we study the arithmetic sum (difference) set K? + K? in I = [0, 1] in terms of the parameters (?, ?) ? I x I, where K? and K? are middle-Cantor sets contained in I. We describe two regions, A and B, in the parameter space (?, ?) where the characterization of the arithmetic sum set K? + K? is given
A Shil'nikov's theorem in R4 in an extended neighborhood of a saddle point of focus - focus type
No full textIn this article we study the existence of chaotic solutions in a neighborhood of a homoclinic orbit of a saddle point of focus-focus type. We will prove that the solutions have an exponential expansion, this fact implies the existence of a subsystem of solutions, which is in one-to-one correspondence with the set of doubly infinite sequences
On branched covering of compact Riemann surfaces with automorphisms
No full textIn this work, we give an algorithm to count the different conformal equivalence classes of compact Riemann surfaces that admit a group of automorphisms isomorphic to Z/nZ, n ? N, and that are branched coverings ofthe Riemann sphere, with signature ((n, 0); m1 ,m2 ,m3 ), m1 ,m2,m3 ? N.By using the previous result, we count the different conformal equivalence classes of compact Riemann surfaces in the cases of coverings with signature ((p, 0); p, p, p), p ? 5 and prime, and signature ((p2, 0); p2 , p2 , p), p ? 3 and prime
Characterizations of a class of matrix transformations
No full textOne of the important investigations in the theory of summability is that of finding characterizations on an infinite matrix in order that the matrix should transform one sequence into another sequence space. In this note we present an abstract matrix transformation theorem. Prom it we can obtain the characterizations of a class of matrix transformations
On the resolution of fredholm integral equations by multigrid domain separation techniques
No full textWe introduce a technique for split discretizations of Fredholm integral equations of the second kind by means of projections on some subsets of quadrature nades. The technique has its roots in the traditional framework of integral operators of the second kind. We combine this approach with two level methods and generate a numerical parallel scheme
Solutions to the prescribed mean curvature equation
No full textWe apply variational methods in order to prove that the nonlinear system (1) admits at least one regular solution
A double inequality related with Burnside’s formula
No full textWe prove the following double inequality related with Burnside's formula for n!
where the constants a*=0.428844044... and a*=0.5 are the best possible. We believe that the method we used in the proof gives insight to undergraduate students to understand how simple inequalities can be established
Appendix A. Results on semigroups
No full textWe recall here some results on generation and regularity properties of a strongly continuous semigroup by a second order, possibly degenerated, differential operator
Saturations of submodules with respect to subsets of a ring
No full textLet R be a commutative ring with identity and M a unital R-module. For any submodule N of M and non-empty subset T of R, let SMT (N)={m ∈ M : rm∈ N for some r ∈ R\T}. In this article we study conditions under which SMT (N) is a submodule of M and investigate when it is a union of prime submodules