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MATTER AT HIGH DENSITY AND PROPERTIES OF NEUTRON STARS |
| Host Laboratory | Scientific Supervisor | |
| University of Oslo Department of Physics POSTBOKS 1048,BLINDERN 0316 Oslo Norway |
PROFESSEUR Eivind Osnes Tel : 47/22856430 / Fax : 47/22856422 Email : eivind.osnes@fys.uio.no | |
| Grant Holder | ||
| Dr. Fabio,Vittorio De Blasio (Italian) Tel : 39/22564880 / Fax : Email : DEBLASIO@NBIVHS.NBI.DK | ||
| Abstract 1) Superfluidity in inhomogeneous hadronic systems. Free neutrons are ex- pected to be superfluid at most of the temperatures and densities typical of a neutron star. Pairing gaps of superfluid neutrons in the crust of the star, expected at densities below ~ 10ll g cm-3 are important parameters for calculations of the dynamics of the star (e.g., pulsar glitches and cooling times). In particular in the calculations of neutron matter one simply considers the system as infinite and homogeneous. However, neutrons move in a very inhomogeneous background due to the presence of nuclei. At first sight, one shouldn't expect Dig differences between the homogeneous and the inhomogeneous system, because in a superconductor the addition of impurities in the lattice doesn't alter the pairing prop- erties of the system (what is referred to as 'Anderson's theorem'). on the other hand, for the superfluid of neutrons inside the crust of a neutron star the coherence length is compa- rable to the typical size of density variations induced by nuclei and thus variations respect to the inhomogeneous case are expected. This problem is encountered also in solid state physics at a different scale, since the sizes of the normal metal and of the superconductor are macroscopic. In previous works, we have used a semiclassical model of superfluidity consisting of a local solution of the BCS equations of superconductivity (2,4,11,19,22). It was found that the inhomogeneities may account for most of the specific heat in the crust of a neutron star, a parameter of interest for cooling calculations. However the semiclassical approximation can fail in the cases where the coherence length of the superfluid is much larger than the nuclei. This is what happens in most of the crust and expecially at high densities. In these regimes one expects a 'proximity effect': the exchange of neutrons be- tween the non-superfluid (normal) nucleus and the environment of superfluid neutrons can induce superfluidity in the nuclei with a suppression outside them. To this purpose, we are applying well-tested solid-state techniques (the quasi-classical Green's function method) to the case of alternate slabs of pure and contamined neutron matter. This geometry, that is found in a neutron star at densities ~ 1014 g cm-3 is also the one more frequently encountered in the solid state counterpart. The first results show that with realistic 'bulk' gaps the reduction factor is not negligible. Contract number : FMBICT971953 | ||
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