The structure of strange quark matter and neutron stars

Theoretical aspects of the structure of strange quark matter and neutron stars are discussed. Recent observations of thermal emissions from compact objects have been used to limit their radiation radii, defined by R _∞, = R/√1-2GM/Rc². Although x-ray observations suggest anomalously small radii, consistent with strange quark matter stars, spectral observations over a broader wavelength range also admit a normal neutron star interpretation. Structures of strange quark and neutron stars are contrasted using known analytic solutions of the relativistic structure equations. These are compared to numerical models utilizing various realistic equations of state for strange quark and nucleonic matter. Potentially observable quantities, such as moments of inertia and binding energies, are discussed. Such comparisons highlight the importance of direct radius measurements. Measurements of quark or neutron star masses also have the potential of setting an upper limit to the energy density in any compact object. Ultimately, such measurements could constrain the possibility of deconfined strange quark matter.