Oak Ridge National Laboratory

Physics Division

Physics Division Seminars

Physics Division Seminars bring us speakers on a variety of physics related subjects. Usually these are held in the Building 6008 large Conference Room, at 3:00 pm on the chosen day, but times and locations may vary. For more information, contact our seminar chairman,

Alfredo Galindo-Uribarri
Tel (Office): (865) 574-6124  (FAX): (865) 574-1268

Thu., April 15, 2010, at 3:00 p.m. (refreshments at 2:40 p.m.)

Equation of State of High Density Matter

Jirina Stone, University of Tennessee, Knoxville & University of Oxford (UK)
Building 6008 Conference Room

Over the last decade, new observational information concerning compact stars has provided evidence to challenge our understanding of the fundamental properties of matter under extreme conditions. The new generation of space observatories provides important data on thermal emission from isolated neutron stars, their cooling history and their radii. The number of known binary pulsars was considerably increased due to improvements in radio telescopes and interferometric techniques allowing extremely precise neutron star mass measurements. New data on bursting millisecond pulsars, kHz quasi-periodic oscillations and half-day long X-ray superbursts are waiting for interpretation. New detectors of gravitational waves are being built, offering exciting prospects for new discoveries.

Microscopic physics of stellar matter is extremely challenging, limited mainly by our still inadequate knowledge of the forces acting between its constituents. Many theoretical models, based on very different physical assumptions, have been developed, giving a tantalizing variety of predictions of properties of symmetric and pure neutron nuclear matter, such as the density dependence of the energy per particle and of the symmetry energy. Predicted properties of neutron stars, such as gravitational mass and radius, also vary widely. A large number of these results are broadly consistent with existing observations. However, it is impossible at present to choose a model (or a class of models) which yield predictions of neutron star properties reliable enough to lead observations in their search for significant data leading to new physics.

In this talk, we give a brief survey of the existing status of nuclear matter models and introduce a new, quark-model-based free nucleon-nucleon interaction, the Oxford potential. Applications of the potential to free nucleon-nucleon scattering data (phase shifts, 1S0 scattering length and effective range) and the properties of the deuteron will be shown to be in a very good agreement with experimental data. Finally, the equation of state of symmetric and asymmetric nuclear matter in the Brueckner-Hartree-Fock approximation will be discussed together with its application in cold non-rotational neutron star models.