Ressonancia parametrica em modelos de estrelas de neutrons
AUTOR(ES)
Sergio Dias Campos
DATA DE PUBLICAÇÃO
2003
RESUMO
The Parametric Resonance phenomenon is nowadays the most accepted model to explain the huge production of matter in the pos-infiationary Universe. In this work we show that this phenomenon can also appears in models of neutron stars describing the production of photons in its interior. The Chapter 1 is a general introduction to the neutron stars. We describe, the behavior of the matter in the interior of this object, we get a Politropic Equation of State and we show as a pion condensate can change the Equation of State. The existence of this condensed is fundamental for our work. The Chapter 2 introduces the phenomenon of Parametric Resonance as it is used in Cosmology, that is, as a mechanism for matter production. This chapter shows, also shortly, the mathematics needed to study this phenomenon. The Chapter 3 is the description of the model of García-Bellido and Kusenko describing the Parametric Resonance phenomenon in the collision among two neutron stars. These authors applied this mechanism of exponential production of matter to explain the jets of gamma-rays detected in high atmosphere, as a result fIam the collision among two neutron stars. After these introductory chapters we show in Chapter 4 our model for matter production in a single neutron star. We used in our model a pion condensate coupled to the electromag- netic field of the neutron star. The solution for the pion condensate appears in the equation of motion for the electromagnetic field as a periodic potential. In this case, the equation of motion for the electromagnetic field is classified as a Lamé s Equation. This equation type presents stable and unstable solutions in the space of parameters. The unstable solutions (resonance bands) describe an exponential photon production. In the Chapter 5 we make an analysis of the particle number and energy density produced in the first resonance band through Parametric Resonance mechanism. N eglecting effects of photon absorption by the surrounding matter we get an exponential production of parti- cles. Nevertheless, absorption effects need to be analyzed more carefully since the photons produced can change the thermal evolution of the star as well modify its Equation of State. Three appendixes complement our work. The first (Appendix A) presents some consi- derations about the Hill s Equation. The second (Appendix B) shows some derivations of formulas used to obtain the Floquet s Exponent. The third shows the Guth s Infiationary Universe. I We finish this work with Final Remarks, where we offer a deeper analysis of our work
ASSUNTO(S)
astrofisica pions objetos compactos
