I will discuss the possible scenarios concerning the composition
of compact stars. In particular I will show that between two to three
times nuclear matter saturation density new degrees of freedom appear, in
particular delta resonances and hyperons. The production of these
particles softens significantly the Equation of State and suggests that
stars made of hadrons are maybe not able to describe the most massive
compact stars.
I will outline the implications of the existence of another family of
compact stars, made (almost) entirely of deconfined quarks, and stable at
masses even much larger than two solar masses. The possible signatures of
this two-family scenario will be discussed, in particular in relation with
the phenomenology of short and long Gamma Ray Bursts and of neutrino
signals.
A.D., A. Lavagno, G. Pagliara, Phys. Rev. D89 (2014) 043014
A.D., A. Lavagno, G. Pagliara, D. Pigato, Phys. Rev. C90 (2014) 065809
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Alessandro Drago
Ferrara University