Phase Transitions in Neutron Stars and Maximum Masses

Using the most recent realistic effective interactions for nuclear matter with a smooth extrapolation to high densities including causality, we constrain the equation of state and calculate maximum masses of rotating neutron stars. First and second order phase transitions to, e.g., quark matter at high densities are included. If neutron star masses of $\sim 2.3M_\odot$ from quasi-periodic oscillations in low mass X-ray binaries are confirmed, a soft equation of state as well as strong phase transitions can be excluded in neutron star cores.Comment: Replaced with revised version, 7 pages, 3 figs. To appear in Ap. J. Let

A bakestones journey to Borgund. An archaeological study of Borgund’s role in the trade of bakestones in Western Norway between the 11th and 16th century

This thesis studies bakestones found in the Medieval town of Borgund, and the town’s position in the commerce network of bakestones in Western Norway. Borgund lies on the sailing route between Trondheim and Bergen, located between some known quarry areas of bakestones in Western Norway. The aim has been to find whether Borgund’s trade was directed south towards Bergen and the quarries of Ølve/Hatlestrand or north towards Trondheim and the quarries of Øye, if there were any temporal changes and if Borgund functioned as a transit port for further distribution of bakestones to nearby areas. Visual archaeological analysis was conducted to find trends in the archaeological material related to the bakestone’s use. A visual geological analysis was conducted to distinguish geological groups and quarry groups among the material. Some of the bakestones were also analysed geochemically using pXRF to see if they matched the visual geological analysis. It was found that most of the bakestones at Borgund were unused, meaning Borgund functioned as a consumer, not as a transit port for further distribution to nearby areas. More than 60% of the bakestones consisted of fine-grained chlorite schist, a quality only found in Ølve/Hatlestrand, meaning the trade of bakestone was mainly directed south to Bergen and Ølve/Hatlestrand. The remaining bakestones could not be provenaced or consisted of medium-grained or coarse-grained chlorite schist. Both materials may occur in Ølve/Hatlestrand and Øye. However, since the traces of bakestone extraction at Øye indicate small-scale production and both the materials clustered with the fine-grained chlorite schist in the geochemical analysis, they are likely from Ølve/Hatlestrand as well.Arkeologi mastergradsoppgaveARK350MAHF-AR

Hyperon effects on the properties of β\beta-stable neutron star matter

We present results from Brueckner-Hartree-Fock calculations for $\beta$-stable neutron star matter with nucleonic and hyperonic degrees of freedom employing the most recent parametrizations of the baryon-baryon interaction of the Nijmegen group. Only $\Sigma^-$ and $\Lambda$ are present up to densities $\sim 7\rho_0$. The corresponding equations of state are then used to compute properties of neutron stars such as masses and radii.Comment: 4 pages, contributed talk at HYP2000, Torino, 23-27 Oct. 200

Indentor-escape, delamination and orogenic collapse of the ca. 600-500 Ma East African/Antarctic Orogen in Mozambique and Dronning Maud Land (East Antarctica)

The East African/Antarctic Orogen (EAAO) is one of the largest orogenic belts on the planet, resulting from the collision of various parts of East and West- Protogondwana between ca. 600 and 550 Ma. The central and southern parts of the orogen are typified by high-grade rocks, representing the overprinted margins of the various colliding continental blocks. New fieldwork and geochronology in northern Mozambique reveals a protracted polyphase Ediacaran/Cambrian deformation history. New age constraints reveal high-grade metamorphism at 600-550 Ma, overprinting and older basement

3P_2-3F_2 pairing in neutron matter with modern nucleon-nucleon potentials

We present results for the $^3P_2 - ^3F_2$ pairing gap in neutron matter with several realistic nucleon-nucleon potentials, in particular with recent, phase-shift equivalent potentials. We find that their predictions for the gap cannot be trusted at densities above $\rho\approx 1.7\rho_0$, where $\rho_0$ is the saturation density for symmetric nuclear matter. In order to make predictions above that density, potential models which fit the nucleon-nucleon phase shifts up to about 1 GeV are required.Comment: Revtex style, 19 pages, 6 figures inlude

Modern nucleon-nucleon potentials and symmetry energy in infinite matter

We study the symmetry energy in infinite nuclear matter employing a non-relativistic Brueckner-Hartree-Fock approach and using various new nucleon-nucleon (NN) potentials, which fit np and pp scattering data very accurately. The potential models we employ are the recent versions of the Nijmegen group, Nijm-I, Nijm-II and Reid93, the Argonne $V_{18}$ potential and the CD-Bonn potential. All these potentials yield a symmetry energy which increases with density, resolving a discrepancy that existed for older NN potentials. The origin of remaining differences is discussed.Comment: 17 pages, 10 figures included, elsevier latex style epsart.st