2,839 research outputs found
Effect of hyperon-hyperon interaction on bulk viscosity and r-mode instability in neutron stars
We investigate the effect of hyperon matter including hyperon-hyperon
interaction on bulk viscosity. Equations of state are constructed within the
framework of a relativistic field theoretical model where baryon-baryon
interaction is mediated by the exchange of scalar and vector mesons.
Hyperon-hyperon interaction is also taken into account by the exchange of two
strange mesons. This interaction results in a smaller maximum mass neutron star
compared with the case without the interaction. The coefficient of bulk
viscosity due to the non-leptonic weak process is determined by these equations
of state. The interacting hyperon matter reduces the bulk viscosity coefficient
in a neutron star interior compared with the no interaction case. The r-mode
instability is more effectively suppressed in hyperon-hyperon interaction case
than that without the interaction.Comment: 25 pages, 10 figures; two new figures added and results and
discussion section revised; final version to appear in PR
Hyperon bulk viscosity in the presence of antikaon condensate
We investigate the hyperon bulk viscosity due to the non-leptonic process in condensed matter and its effect
on the r-mode instability in neutron stars. We find that the hyperon bulk
viscosity coefficient in the presence of antikaon condensate is suppressed
compared with the case without the condensate. The suppressed hyperon bulk
viscosity in the superconducting phase is still an efficient mechanism to damp
the r-mode instability in neutron stars.Comment: AASTeX; 21 pages including 5 figures; change in the title and
replaced by the revised versio
Probing dense matter in neutron stars with axial w-modes
We study the problem of extracting information about composition and equation
of state of dense matter in neutron star interior using axial w-modes. We
determine complex frequencies of axial w-modes for a set of equations of state
involving hyperons as well as Bose-Einstein condensates of antikaons adopting
the continued fraction method. Hyperons and antikaon condensates result in
softer equations of state leading to higher frequencies of first axial w-modes
than that of nuclear matter case, whereas the opposite happens in case of
damping times. The presence of condensates may lead to the appearance of a new
stable branch of superdense stars beyond the neutron star branch called the
third family. The existence of same mass compact stars in both branches are
known as neutron star twins. Further investigation of twins reveal that first
axial w-mode frequencies of superdense stars in the third family are higher
than those of the corresponding twins in the neutron star branch.Comment: LaTeX; 23 pages including two tables and 11 figure
A new approach to bulk viscosity in strange quark matter at high densities
A new method is proposed to compute the bulk viscosity in strange quark
matter at high densities. Using the method it is straightforward to prove that
the bulk viscosity is positive definite, which is not so easy to accomplish in
other approaches especially for multi-component fluids like strange quark
matter with light up and down quarks and massive strange quarks.Comment: 7pages, talk given in SQM2008. Minor revisions, including
clarification and updated reference
Bulk viscosity and r-modes of neutron stars
The bulk viscosity due to the non-leptonic process involving hyperons in
condensed matter is discussed here. We find that the bulk viscosity is
modified in a superconducting phase. Further, we demonstrate how the exotic
bulk viscosity coefficient influences -modes of neutron stars which might be
sources of detectable gravitational waves.Comment: 4 page, 2 figures; presented in the Quark Matter 2008 held in Jaipur,
India from 4-10 February, 2008; to be published in J. Phys.
Evaporation of alpha particles from P nucleus
The energy spectra of alpha particles have been measured in coincidence with
the evaporation residues for the decay of the compound nucleus P produced
in the reaction F (96 MeV) + C. The data have been compared with the
predictions of the statistical model code CASCADE. It has been observed that
significant deformation effect in the compound nucleus need to be considered in
order to explain the shape of the evaporated alpha particle energy spectra.Comment: 4 pages, 3 figures, revtex, epsf styl
Exclusive light particle measurements for the system F + C at 96 MeV
Decay sequence of hot {31}^P nucleus has been investigated through
exclusive light charged particle measurements in coincidence with individual
evaporation residues using the reaction {19}^F (96 MeV) + {12}^C.
Information on the sequential decay chain have been extracted by confronting
the data with the predictions of the statistical model. It is observed from the
present analysis that such exclusive light charged particle data may be used as
a powerful tool to probe the decay sequence of the hot light compound systems.Comment: 13 pages, 8 figures, Physical Review C (in press
- …