Study of spin polarized nuclear matter and finite nuclei with finite range simple effective interaction

The properties of spin polarized pure neutron matter and symmetric nuclear matter are studied using the finite range simple effective interaction, upon its parametrization revisited. Out of the total twelve parameters involved, we now determine ten of them from nuclear matter, against the nine parameters in our earlier calculation, as required in order to have predictions in both spin polarized nuclear matter and finite nuclei in unique manner being free from uncertainty found using the earlier parametrization. The information on the effective mass splitting in polarized neutron matter of the microscopic calculations is used to constrain the one more parameter, that was earlier determined from finite nucleus, and in doing so the quality of the description of finite nuclei is not compromised. The interaction with the new set of parameters is used to study the possibilities of ferromagnetic and antiferromagnetic transitions in completely polarized symmetric nuclear matter. Emphasis is given to analyze the results analytically, as far as possible, to elucidate the role of the interaction parameters involved in the predictions.

Reaseguro Finite Risk en ambiente financiero estocástico

Una de las características del reaseguro finite risk es la existencia de una cuenta de experiencia, que está formada por las primas que cobra el reasegurador, junto con su rendimiento financiero,y su finalidad es financiar los siniestros que éste ha de satisfacer a la cedente en el plazo establecido. El objetivo de este trabajo es diseñar un modelo que permita determinar el saldo estimado o reserva que debe de tener en cada periodo anual la cuenta de experiencia para garantizar su solvencia dinámica, teniendo en cuenta la experiencia de siniestralidad de la cartera del reasegurador y de cada cedente. Para el cálculo de la prima de reaseguro y del saldo de la cuenta de experiencia se asumirá ambiente financiero estocástico, de modo que la prima de reaseguro dependerá también de otros parámetros como la volatilidad del tipo de interés o de la aversión al riesgo.

Finite-temperature T matrix in a real-time formalism

A generalized off-shell unitarity relation for the two-body scattering T matrix in a many-body medium at finite temperature is derived, through a consistent real-time perturbation expansion by means of Feynman diagrams. We comment on perturbation schemes at finite temperature in connection with an erroneous formulation of the Dyson equation in a paper recently published.