ALTRUISM, EGOISM AND GROUP COHESION IN A LOCAL INTERACTION MODEL

In this paper we have introduced and parameterized the concept of ?group cohesion? in a model of local interaction with a population divided into groups. This allows us to control the level of ?isolation? of these groups: We thus analyze if the degree of group cohesion is relevant to achieve an efficient behaviour and which level would be the best one for this purpose. We are interested in situations where there is a trade off between efficiency and individual incentives. This trade off is stronger when the efficient strategy or norm is strictly dominated, as in the Prisoner?s Dilemma or in some cases of Altruism. In our model we have considered that agents could choose to be Altruist of Egoist, in fact, they behave as in Eshel, Samuelson and Shaked (1998) model.Group Cohesion, Cooperation, Local Interaction, Altruism, Group selection.

Radiative corrections to all charge assignments of heavy quark baryon semileptonic decays

In semileptonic decays of spin-1/2 baryons containing heavy quarks up to six charge assignments for the baryons and lepton are possible. We show that the radiative corrections to four of these possibilities can be directly obtained from the final results of the two possibilities previously studied. There is no need to recalculate integrals over virtual or real photon momentum or any traces.Comment: 15 pages, 2 figures, RevTex. Extended discussion. Final version to appear in Physical Review

Aportes de la historia de la ciencia a la formación permanente del profesorado universitario. Un caso en el área de la Fisicoquímica

En este documento se presenta el reporte de un trabajo de investigación cuyos referentes están dados a partir de las relaciones entre la historia, la filosofía y la didáctica de las ciencias. El estudio se realizó con el propósito de indagar los aportes que genera la historia de la ciencia en la formación del profesorado, para lo cual se desarrollo con la participación voluntaria de profesores de química a nivel universitario. El estudio se enmarca desde una perspectiva cualitativa ubicado desde una visión interpretativa y se analizan los resultados mediante estudios de caso. Se presenta el caso de un profesor de fisicoquímica quien, mediante un trabajo en equipo, diseño una unidad didáctica para la enseñanza del concepto de calor específico, haciendo uso del calorímetro de Lavoisier, dirigida a profesores de química en formación inicial

La experiencia del arte

Fil: García Martínez, J. A.

Van der Waals spin valves

We propose spin valves where a 2D non-magnetic conductor is intercalated between two ferromagnetic insulating layers. In this setup, the relative orientation of the magnetizations of the insulating layers can have a strong impact on the in-plane conductivity of the 2D conductor. We first show this for a graphene bilayer, described with a tight-binding model, placed between two ferromagnetic insulators. In the anti-parallel configuration, a band gap opens at the Dirac point, whereas in the parallel configuration, the graphene bilayer remains conducting. We then compute the electronic structure of graphene bilayer placed between two monolayers of the ferromagnetic insulator CrI$_3$, using density functional theory. Consistent with the model, we find that a gap opens at the Dirac point only in the antiparallel configuration.Comment: 5 pages, 4 figure