68 research outputs found
Exotic bulk viscosity and its influence on neutron star r-modes
We investigate the effect of exotic matter in particular, hyperon matter on
neutron star properties such as equation of state (EoS), mass-radius
relationship and bulk viscosity. Here we construct equations of state within
the framework of a relativistic field theoretical model. As hyperons are
produced abundantly in dense matter, hyperon-hyperon interaction becomes
important and is included in this model. Hyperon-hyperon interaction gives rise
to a softer EoS which results in a smaller maximum mass neutron star compared
with the case without the interaction. Next we compute the coefficient of bulk
viscosity and the corresponding damping time scale due to the non-leptonic weak
process including hyperons. Further, we investigate the role of the
bulk viscosity on gravitational radiation driven r-mode instability in a
neutron star of given mass and temperature and find that the instability is
effectively suppressed.Comment: 5 pages, 3 figure, presented in the Conference on Isolated Neutron
Stars: From the Interior to The Surface, London, UK, 24-28 April, 2006;
revised and final version to appear in Astrophys. Space Sc
Linear Paul trap design for an optical clock with Coulomb crystals
We report on the design of a segmented linear Paul trap for optical clock
applications using trapped ion Coulomb crystals. For an optical clock with an
improved short-term stability and a fractional frequency uncertainty of 10^-18,
we propose 115In+ ions sympathetically cooled by 172Yb+. We discuss the
systematic frequency shifts of such a frequency standard. In particular, we
elaborate on high precision calculations of the electric radiofrequency field
of the ion trap using the finite element method. These calculations are used to
find a scalable design with minimized excess micromotion of the ions at a level
at which the corresponding second- order Doppler shift contributes less than
10^-18 to the relative uncertainty of the frequency standard
Color superconducting quark matter core in the third family of compact stars
We investigate first order phase transitions from -equilibrated
hadronic matter to color flavor locked quark matter in compact star interior.
The hadronic phase including hyperons and Bose-Einstein condensate of
mesons is described by the relativistic field theoretical model with density
dependent meson-baryon couplings. The early appearance of hyperons and/or
Bose-Einstein condensate of mesons delays the onset of phase transition
to higher density. In the presence of hyperons and/or condensate, the
overall equations of state become softer resulting in smaller maximum masses
than the cases without hyperons and condensate. We find that the maximum
mass neutron stars may contain a mixed phase core of hyperons, condensate
and color superconducting quark matter. Depending on the parameter space, we
also observe that there is a stable branch of superdense stars called the third
family branch beyond the neutron star branch. Compact stars in the third family
branch may contain pure color superconducting core and have radii smaller than
those of the neutron star branch. Our results are compared with the recent
observations on RX J185635-3754 and the recently measured mass-radius
relationship by X-ray Multi Mirror-Newton Observatory.Comment: 24 pages, RevTex, 9 figures included; section II shortened, section
III elaborated, two new curves in Fig. 9 and acknowledgements added; version
to bepublished in Phys. Rev.
Quark Stars: Features and Findings
Under extreme conditions of temperature and/or density, quarks and gluons are
expected to undergo a deconfinement phase transition. While this is an
ephemeral phenomenon at the ultra-relativistic heavy-ion collider (BNL-RHIC),
quark matter may exist naturally in the dense interior of neutron stars.
Herein, we present an appraisal of the possible phase structure of dense quark
matter inside neutron stars, and the likelihood of its existence given the
current status of neutron star observations. We conclude that quark matter
inside neutron stars cannot be dismissed as a possibility, although recent
observational evidence rules out most soft equations of state.Comment: Contribution to proceedings of Hot Quarks 2006, Villasimius, Italy; 5
pages (TeX), 2 .eps figure
Spin Down of Rotating Compact Magnetized Strange Stars in General Relativity
We find that in general relativity slow down of the pulsar rotation due to
the magnetodipolar radiation is more faster for the strange star with
comparison to that for the neutron star of the same mass. Comparison with
astrophysical observations on pulsars spindown data may provide an evidence for
the strange star existence and, thus, serve as a test for distinguishing it
from the neutron star.Comment: 6 pages; Accepted for publication in Astrophysics and Space Scienc
Interaction between bovine trypsin and a synthetic peptide containing 28 residues of the bait region of human α2-macroglobulin
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