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Neutron starmass and radius measurements are becoming sufficiently accurate as to offer astrophysical constraints on the properties of neutron-rich matter near the nuclear saturation density. Current observations, which imply that the radius of a 1.4 solar mass neutron star lies between 10.4 and 12.9 km, also imply that 43 < L < 67 MeV, where L is a parameter describing the slope of the nuclear symmetry energy and that the neutron skin thickness in lead is relatively small.

Both the Fermi breakup (FBM) and the Statistical Multifragmentation (SMM) models provide prescriptions for calculating mass and charge distributions and multiplicities of the fragments emitted in the breakup of an excited nuclear system. Although they are usually formulated in different terms and applied in very different regions of mass and excitation energy, they are essentially one and the same model. We make this close relationship explicit and compare results of calculations using the FBM in use today and the one proposed here. We then show how the FBM/SMM is related to the usual compound nucleus evaporation model and how the two might be unified and extended to provide a comprehensive description of statistical nuclear decay.

A self‐consistent model of the neutron star crust is described, including a discussion of some of the primary physics challenges: the description of low‐density neutron matter and the nuclear symmetry energy. Though often used, Skyrme models fail to describe low‐density neutron matter accurately. The model also shows that the nuclear symmetry energy is the most significant uncertainty in the description of the crust, and strongly controls the composition. The model is applied to the computation of the shear modulus, which is relevant for modeling the frequencies of quasi‐periodic oscillations in giant flares produced by magnetars. A clear correlation between the symmetry energy and the shear modulus is elucidated.

If strange quark matter is absolutely stable, some neutron stars may be strange quark stars. Strange quark stars are usually assumed to have a simple liquid surface. We show that if the surface tension of droplets of quark matter in the vacuum is sufficiently small, droplets of quark matter on the surface of a strange quark star may form a solid crust on top of the strange quark star. This solid crust can significantly modify the predictions for the photon emission for the surface in an observable way.

Heavy‐ion reactions induced by neutron‐rich nuclei provide the unique opportunity in terrestrial laboratories to constrain the nuclear symmetry energy Esym in a broad density range. A conservative constraint, 32(ρ/ρ0)0.7 < Esym(ρ) < 32(ρ/ρ0)1.1, around the nuclear matter saturation density ρ0 has recently been obtained from analyzing the isospin diffusion data within a transport model for intermediate energy heavy‐ion reactions. This subsequently puts a stringent constraint on properties of neutron stars, especially their radii and cooling mechanisms.

The presence of quark matter in neutron stars may affect several neutron star observables and the neutrino signal in core-collapse supernovae. These observables are sensitive to the phase of quark matter that is present in compact objects. We present the first calculation of the phase structure of dense quark matter which includes a six-fermion color-superconducting interaction and show that the effect of this term can destabilize the pairing interaction, favoring phases where fewer quarks are paired. In turn, this modification of the phase structure can modify the neutrino signal, the structure of the neutron star, and the long-term cooling. We also show that, contrary to the 20-year old paradigm of the surface structure of the "strange-quark stars", the surface of these objects may consist of nuggets of strange quark matter screened by the electron gas., 3 pages; PANIC05 conference proceedings