Apresentamos um formalismo matricial, inspirado nos tetravetores de Minkowski da teoria da relatividade, útil para resolver problemas de física clássica relacionados com mecânica e termodinâmica. O formalismo é especialmente conveniente quando se aplica a exercícios que envolvam forças não conservativas e produção ou destruição de energia mecânica. Por outro lado, o formalismo permite lidar de forma direta com mudanças de referencial de inércia pois ele incorpora o princípio da relatividade. Para melhor se apreciar o seu funcionamento, aplicamos o formalismo a alguns casos concretos.

We present a matrix formalism, inspired by the Minkowski four-vectors of special relativity, useful to solve classical physics problems related to both mechanics and thermodynamics. The formalism turns out to be convenient to deal with exercises involving non-conservative forces and production or destruction of mechanical energy. On the other hand, it provides a framework to treat straightforwardly changes of inertial reference frames, since it embodies the Principle of Relativity. We apply the formalism to a few cases to better show how it works.

Recent results obtained in the Chromodielectric Model (CDM) have shown that strange quark matter at very high densities may appear in two phases, namely a chiral broken and a chiral symmetric phase, which may not be absolutely stable. In the chiral symmetric phase, the abundance of the quarks flavors u, d and s is the same and there are no electrons. In this paper we study an extended version of the Chromodielectric model (CDM) with a BCS quark pairing implemented, and analyze the superconducting color flavor locked phase. We show that the inclusion in the free energy density of a negative term of the diquark condensate guarantees the stability of quark matter. We also analyze the phase transition between matter described by different equations of state and only find a first order transition, at a very low pressure, from the CFL phase to the unpaired strange quark matter, which opens the possibility for a quark-hadron phase transition. Our study has implications in astrophysics, in particular regarding the formation and the structure of compact quark stars. We explicitly show that CFL stars can be absolutely stable and more compact than strange stars.

We use the Peierls-Yoccoz projection method to evaluate the center-of-mass correction of a relativistic system of nucleons and sigma and omega mesons, described in a mean-field Hartree approach. This correction for 4He, 16O and 40Ca is compared with the pure harmonic oscillator center-of-mass energy correction.