An exact solution to the Dirac equation for a time dependent Hamiltonian in 1-1D space-time

We find an exact solution to the Dirac equation in 1-1 dimensional space-time in the presence of a time-dependent potential which consists of a combination of electric, scalar, and pseudoscalar terms.Comment: Five page

The role of Central American Trade in developing El Salvador’s high-value exports

This paper describes the development and evolution of El Salvador’s industrial exports. This paper found that El Salvador’s exports to other Central American countries enhance business opportunities observed in an increase in the number of new products exported to this region and this products are more complex compared to the regular exports outside region. However, this paper also finds that the products that are exported first to Central America and then to the rest of the world are not the most sophisticated. El Salvador may benefit from trade diversion that prevents it from exporting high quality products to the world except Central America.Titulo original en español: Evolución y desarrollo de la complejidad de las exportaciones del sector industrial salvadoreño en los últimos 20 año

Graphical representation and generalization in sequences problems

In this paper we present different ways used by Secondary students to generalize when they try to solve problems involving sequences. 359 Spanish students solved generalization problems in a written test. These problems were posed through particular terms expressed in different representations. We present examples that illustrate different ways of achieving various types of generalization and how students express generalization. We identify graphical representation of generalization as a useful tool of getting other ways of expressing generalization, and we analyze its connection with other ways of expressing it

On the Dirac equation with PT-symmetric potentials in the presence of position-dependent mass

The relativistic problem of fermions subject to a PT-symmetric potential in the presence of position-dependent mass is reinvestigated. The influence of the PT-symmetric potential in the continuity equation and in the orthonormalization condition are analyzed. In addition, a misconception diffused in the literature on the interaction of neutral fermions is clarified.Comment: 8 page

Unsuitable use of spin and pseudospin symmetries with a pseudoscalar Cornell potential

The concepts of spin and pseudospin symmetries has been used as mere rhetorics to decorate the pseudoscalar potential [Chin. Phys. B 22 090301 (2013)]. It is also pointed out that a more complete analysis of the bound states of fermions in a a pseudoscalar Cornell potential has already been published elsewhere.Comment: 6 pages, to appear in Chi. Phys.

On the bound-state spectrum of a nonrelativistic particle in the background of a short-ranged linear potential

The nonrelativistic problem of a particle immersed in a triangular potential well, set forth by N.A. Rao and B.A. Kagali, is revised. It is shown that these researchers misunderstood the full meaning of the potential and obtained a wrong quantization condition. By exploring the space inversion symmetry, this work presents the correct solution to this problem with potential applications in electronics in a simple and transparent way