Selecciones Matemáticas

5

Authors: Nélida Medina García

We consider the ring of polynomials R = K[x1, dots,xn] in the variables x1, dots,xn and complex coefficients. The permutation group of 1, dots,n acts sore R by permuting the variables. The set of invariants by this action forms a ring generated by elementary symmetric polynomials. Emmy Noether proves that if a finite group of inverse matrices G subsetGL(n;k) acts on R, then the ring of invariants is generated by a finite number of invariant homogeneous and defines an operator in G to obtain invariant polynomials. There are algebraic relationships between the generators of the invariant ring and the orbits of Cn/G. In 1963, Masayoshi Nagata demonstrated that the ring of the invariants of geomagically reductive groups is finitely generated. We analice the existence of a quotient variety X/G where G is an algebraic group acting on an algebraic variety X.

8

Authors: César Torres Ledesma

In this paper we consider the fractional Hamiltonian system given by (0.2) −tDα T(0Dα t u(t)) = ∇F(t,u(t)), a.e t ∈ [0,T] u(0) = u(T) = 0. where α ∈ (1/2,1), t ∈ [0,T],u∈Rn, F : [0,T]×Rn →R is a given function and ∇F(t,u) is the gradient of F at u. The novelty of this paper is that, using a modified version of mountain pass theorem for functional bounded from below we prove the existence of at least three solutions for (0.2).

10

Authors: Obidio Rubio

In this paper we present an estimate of the posterior error of finite element-constructed finite element meshes and finite element discontinuous over time for the transport equation of CO2 in the bags Alveolar cells of the human lung, using the dual weighted residual method (DWR).

12

Authors: Liliana Puchuri Medina

The classic Lotka-Volterra model belongs to a family of differential equations known as “Generalized Lotka-Volterra”, which is part of a classification of four models of quadratic fields with center. These models have been studied to address the Hilbert infinitesimal problem, which consists in determine the number of limit cycles of a perturbed hamiltonian system with center. In this work, we first present an alternative proof of the existence of centers in Lotka-Volterra predator-prey models. This new approach is based in algebraic equations given by Kapteyn, which arose to answer Poincar´e’s problem for quadratic fields. In addition, using Hopf Bifurcation theorem, we proof that more realistic models, obtained by a non-linear perturbation of a classic Lotka-Volterra model, also possess limit cycles.

13

Authors: Yuri Sampaio Maluf

This paper discusses the Hawkes process to modeling of the offering book, especially the ETF it iShare Ibovespa index fund. The study aimed to investigate the dynamics of the influences of the offers in relation to the past orders. We study too to the interaction of the order rates of the opposing sides of the Book. Another point addressed is the verification of the operating strategy that captures the dynamics studied. At the first moment, the univariate approach was performed and in the second moment the multivariate of the Hawkes process. The results show that in both cases the Hawkes process it fits well to the data. The fit model indicates that agents have similar behaviors when they act as buyers or sellers of assets. As for the strategy, it was not possible to establish spare gains from changes in bid rates. However, these results are due to the it bid-ask spread more that the predictive capacity of the functions.

20

Authors: Julio Becerra Saucedo

This article presents an analytical study on the local and global existence of the solution of diffusion - reaction problem. We show that if the solution exists locally then, it blows up in finite time. This result covers the case that the solution exists globally. We concluded that the maximum time of existence of the solution depends on the domain, the term representing the reaction in the equation and a test function defined in this job. Likewise we propose the possibility of extending the local existence to the global one using the proper solution framework.