235 research outputs found
Derivation of Amplitude Equations by Renormalization Group Method
A proper formulation in the perturbative renormalization group method is
presented to deduce amplitude equations. The formulation makes it possible not
only avoiding a serious difficulty in the previous reduction to amplitude
equations by eliminating all of the secular terms but also consistent
derivation of higher-order correction to amplitude equations.Comment: 6 page, revte
X-ray Dust Scattering at Small Angles: The Complete Halo around GX13+1
The exquisite angular resolution available with Chandra should allow
precision measurements of faint diffuse emission surrounding bright sources,
such as the X-ray scattering halos created by interstellar dust. However, the
ACIS CCDs suffer from pileup when observing bright sources, and this creates
difficulties when trying to extract the scattered halo near the source. The
initial study of the X-ray halo around GX13+1 using only the ACIS-I detector
done by Smith, Edgar & Shafer (2002) suffered from a lack of sensitivity within
50'' of the source, limiting what conclusions could be drawn.
To address this problem, observations of GX13+1 were obtained with the
Chandra HRC-I and simultaneously with the RXTE PCA. Combined with the existing
ACIS-I data, this allowed measurements of the X-ray halo between 2-1000''.
After considering a range of dust models, each assumed to be smoothly
distributed with or without a dense cloud along the line of sight, the results
show that there is no evidence in this data for a dense cloud near the source,
as suggested by Xiang et al. (2005). Finally, although no model leads to
formally acceptable results, the Weingartner & Draine (2001) and nearly all of
the composite grain models from Zubko, Dwek & Arendt (2004) give poor fits.Comment: 8 pages, 6 figures, accepted for publication in Ap
Renormalization Group Method and Reductive Perturbation Method
It is shown that the renormalization group method does not necessarily
eliminate all secular terms in perturbation series to partial differential
equations and a functional subspace of renormalizable secular solutions
corresponds to a choice of scales of independent variables in the reductive
perturbation method.Comment: 5 pages, late
Anti-phase Modulation of Electron- and Hole-like States in Vortex Core of Bi2Sr2CaCu2Ox Probed by Scanning Tunneling Spectroscopy
In the vortex core of slightly overdoped Bi2Sr2CaCu2Ox, the electron-like and
hole-like states have been found to exhibit spatial modulations in anti-phase
with each other along the Cu-O bonding direction. Some kind of
one-dimensionality has been observed in the vortex core, and it is more clearly
seen in differential conductance maps at lower biases below +-9 mV
Optimised Curing of Silver Ink Jet Based Printed Traces
Manufacturing electronic devices by printing techniques with low temperature
sintering of nano-size material particles can revolutionize the electronics
industry in coming years. The impact of this change to the industry can be
significant enabling low-cost products and flexibility in manufacturing.
implementation of a new production technology with new materials requires
thorough elementary knowledge creation. It should be noticed that although some
of first electronic devices ideally can be manufactured by printing, at the
present several modules are in fact manufactured by using hybrid techniques
(for instance photolithography, vapor depositions, spraying, etc...).Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Exact Solutions for Domain Walls in Coupled Complex Ginzburg - Landau Equations
The complex Ginzburg Landau equation (CGLE) is a ubiquitous model for the
evolution of slowly varying wave packets in nonlinear dissipative media. A
front (shock) is a transient layer between a plane-wave state and a zero
background. We report exact solutions for domain walls, i.e., pairs of fronts
with opposite polarities, in a system of two coupled CGLEs, which describe
transient layers between semi-infinite domains occupied by each component in
the absence of the other one. For this purpose, a modified Hirota bilinear
operator, first proposed by Bekki and Nozaki, is employed. A novel
factorization procedure is applied to reduce the intermediate calculations
considerably. The ensuing system of equations for the amplitudes and
frequencies is solved by means of computer-assisted algebra. Exact solutions
for mutually-locked front pairs of opposite polarities, with one or several
free parameters, are thus generated. The signs of the cubic gain/loss, linear
amplification/attenuation, and velocity of the coupled-front complex can be
adjusted in a variety of configurations. Numerical simulations are performed to
study the stability properties of such fronts.Comment: Journal of the Physical Society of Japan, in pres
Thermonuclear Stability of Material Accreting onto a Neutron Star
We present a global linear stability analysis of nuclear fuel accumulating on
the surface of an accreting neutron star and we identify the conditions under
which thermonuclear bursts are triggered. The analysis reproduces all the
recognized regimes of hydrogen and helium bursts, and in addition shows that at
high accretion rates, near the limit of stable burning, there is a regime of
``delayed mixed bursts'' which is distinct from the more usual ``prompt mixed
bursts.'' In delayed mixed bursts, a large fraction of the fuel is burned
stably before the burst is triggered. Bursts thus have longer recurrence times,
but at the same time have somewhat smaller fluences. Therefore, the parameter
alpha, which measures the ratio of the energy released via accretion to that
generated through nuclear reactions in the burst, is up to an order of
magnitude larger than for prompt bursts. This increase in alpha near the
threshold of stable burning has been seen in observations. We explore a wide
range of mass accretion rates, neutron star radii and core temperatures, and
calculate a variety of burst properties. From a preliminary comparison with
data, we suggest that bursting neutron stars may have hot cores, with T_{core}
>~ 10^{7.5} K, consistent with interior cooling via the modified URCA or
similar low-efficiency process, rather than T_{core} ~ 10^7 K, as expected for
the direct URCA process. There is also an indication that neutron star radii
are somewhat small <~ 10 km. Both of these conclusions need to be confirmed by
comparing more careful calculations with better data.Comment: 67 pages, 19 figures, final version to appear in The Astrophysical
Journal, vol. 599, no. 1, Dec. 10, 200
- …