4,478 research outputs found
Identification of the white dwarf companion to millisecond pulsar J2317+1439
We report identification of the optical counterpart to the companion of the
millisecond pulsar J2317+1439. At the timing position of the pulsar, we find an
object with , and . The
magnitudes and colors of the object are consistent with it being a white dwarf.
By comparing with white dwarf cooling models, we estimate that it has a mass of
M, an effective temperature of
K and a cooling age of Gyr. Combining our
results with published constraints on the orbital parameters obtained through
pulsar timing, we estimate the pulsar mass to be
M. Although the constraint on the pulsar mass is still weak, there is
a significant possibility that the pulsar could be more massive than two solar
mass.Comment: 7 pages, 6 figures, accepted for publication in Ap
D_s spectrum and leptonic decays with Fermilab heavy quarks and improved staggered light quarks
We present preliminary results for the D_s meson spectrum and decay constants
in unquenched lattice QCD. Simulations are carried out with 2+1 dynamical
quarks using gauge configurations generated by the MILC collaboration. We use
the ``asqtad'' a^2 improved staggered action for the light quarks, and the
clover heavy quark action with the Fermilab interpretation. We compare our
spectrum results with the newly discovered 0+ and 1+ states in the D_s system.Comment: 3pp. Presented at 21st International Symposium on Lattice Field
Theory (LATTICE 2003), Tsukuba, Ibaraki, Japan, 15-19 Jul 200
Strong mass effect on ion beam mixing in metal bilayers
Molecular dynamics simulations have been used to study the mechanism of ion
beam mixing in metal bilayers. We are able to explain the ion induced
low-temperature phase stability and melting behavior of bilayers using only a
simple ballistic picture up to 10 keV ion energies. The atomic mass ratio of
the overlayer and the substrate constituents seems to be a key quantity in
understanding atomic mixing. The critical bilayer mass ratio of
is required for the occurrence of a thermal spike (local melting) with a
lifetime of ps at low-energy ion irradiation (1 keV) due to a
ballistic mechanism. The existing experimental data follow the same trend as
the simulated values.Comment: 4 pages, 4 figures, preprin
Magnetic properties of exactly solvable doubly decorated Ising-Heisenberg planar models
Applying the decoration-iteration procedure, we introduce a class of exactly
solvable doubly decorated planar models consisting both of the Ising- and
Heisenberg-type atoms. Exact solutions for the ground state, phase diagrams and
basic physical quantities are derived and discussed. The detailed analysis of
the relevant quantities suggests the existence of an interesting quantum
antiferromagnetic phase in the system.Comment: 9 pages, 9 figures, submitted to Physical Review
Properties of charmonium in lattice QCD with 2+1 flavors of improved staggered sea quarks
We use the dynamical gluon configurations provided by the MILC collaboration
in a study of the charmonium spectrum and psi leptonic width. We examine sea
quark effects on mass splitting and on the leptonic decay matrix element for
light masses as low as m_s/5, while keeping the strange quark mass fixed and
the lattice spacing nearly constant.Comment: Lattice2003(heavy
Semileptonic decays of mesons in unquenched lattice QCD
We present our preliminary results for semileptonic form factors of
mesons in unquenched lattice QCD. Simulations are carried out with
dynamical quarks using gauge configurations generated by the MILC
collaboration. For the valence quarks, we adopt an improved staggered light
quark action and the clover heavy quark action. Our results for and
form factors at are in agreement with the experimental
values.Comment: Lattice2003(heavy), 3 page
On the use of balking for estimation of the blocking probability for OBS routers with FDL lines
Trabajo presentado en la International Conference on Information Networking (ICOIN) 2006, Sendai (Japón), 16-19 de enero de 2006This paper deals with estimation of blocking probabilities
for OBS switches with Fiber Delay Lines (FDLs) and full wavelength
conversion. An incoming burst that finds the wavelengths occupied is
temporarily stored in a FDL. Hence, contention will be sorted out successfully if the residual life of the system is smaller than the maximum
FDL delay. In order to derive the blocking probability, the most accurate methodology to date is the use of balking systems [1–4]. Even though
the approach is accurate for very short lengths of the FDLs we identify
the cases in which inaccuracy is detected. This happens precisely when
the system works with low loss probabilities. Mainly for large number of
wavelengths on the fibers and values of the FDL length at least in the
vicinity of the burst service time.This work was funded by Spanish MEC (project CAPITAL subproject code:
TEC2004-05622-C04-04 and project PINTA
Continuous metal-insulator transition of the antiferromagnetic perovskite NaOsO3
Newly synthesized perovskite NaOsO3 shows Curie-Weiss metallic nature at high
temperature and suddenly goes into an antiferromagnetically insulating state at
410 K on cooling. Electronic specific heat at the low temperature limit is
absent, indicating that the band gap fully opens. In situ observation in
electron microscopy undetected any lattice anomalies in the vicinity of the
transition temperature. It is most likely that the antiferromagnetic
correlation plays an essential role of the gap opening.Comment: 13 pages, 5 figures, PHYS. REV. B 80, 161104(R),(2009
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