17 research outputs found
Neutron Star Superfluidity, Dynamics and Precession
Basic rotational and magnetic properties of neutron superfluids and proton
superconductors in neutron stars are reviewed. The modes of precession of the
neutron superfluid are discussed in detail. We emphasize that at finite
temperature, pinning of superfluid vortices does not offer any constraint on
the precession. Any pinning energies can be surmounted by thermal activation
and there exists a dynamical steady state in which the superfluid follows the
precession of the crust at a small lag angle between the crust and superfluid
rotation velocity vectors. At this small lag the system is far from the
critical conditions for unpinning, even if the observed precession of the crust
may entail a large angle between the figure axis and the crust's rotation
velocity vector. We conclude that if long period modulations of pulse arrival
times and pulse shapes observed in a pulsar like the PSR B1828-11 are due to
the precession of the neutron star, this does not have any binding implications
about the existence of pinning by flux lines or the existence of Type II
superconductivity in the neutron star.Comment: 21 pages, one figure, to appear in the Proceedings of the NATO-ASI
"The Electromagnetic Spectrum of Neutron Stars" held in Marmaris, Turkey,
June 2004, eds. A. Baykal, S.K. Yerli, C. Inam and S. Grebene
The Impact of Divergence Time on the Nature of Population Structure: An Example from Iceland
The Icelandic population has been sampled in many disease association studies, providing a strong motivation to understand the structure of this population and its ramifications for disease gene mapping. Previous work using 40 microsatellites showed that the Icelandic population is relatively homogeneous, but exhibits subtle population structure that can bias disease association statistics. Here, we show that regional geographic ancestries of individuals from Iceland can be distinguished using 292,289 autosomal single-nucleotide polymorphisms (SNPs). We further show that subpopulation differences are due to genetic drift since the settlement of Iceland 1100 years ago, and not to varying contributions from different ancestral populations. A consequence of the recent origin of Icelandic population structure is that allele frequency differences follow a null distribution devoid of outliers, so that the risk of false positive associations due to stratification is minimal. Our results highlight an important distinction between population differences attributable to recent drift and those arising from more ancient divergence, which has implications both for association studies and for efforts to detect natural selection using population differentiation
Reheating neutron stars with the annihilation of self-interacting dark matter
[[abstract]]Compact stellar objects such as neutron stars (NS) are ideal places for capturing dark matter (DM) particles. We study the effect of self-interacting DM (SIDM) captured by nearby NS that can reheat it to an appreciated surface temperature through absorbing the energy released due to DM annihilation. When DM-nucleon cross section ÏÏn is small enough, DM self-interaction will take over the capture process and make the number of captured DM particles increased as well as the DM annihilation rate. The corresponding NS surface temperature resulted from DM self-interaction is about hundreds of Kelvin and is potentially detectable by the future infrared telescopes. Such observations could act as the complementary probe on DM properties to the current DM direct searches.[[notice]]èŁæŁćź
Volcano load control on dyke propagation and vent distribution: Insights from analogue modeling
International audienc