31,974 research outputs found
Constraints on asymmetry of the proton in chiral effective theory
We compute the asymmetry in the proton in chiral effective theory,
using phenomenological constraints based upon existing data. Unlike previous
meson cloud model calculations, which accounted for kaon loop contributions
with on-shell intermediate states alone, this work includes off-shell terms and
contact interactions, which impact the shape of the difference. We
identify a valence-like component of which is balanced by a
-function contribution to at , so that the integrals
of and over the experimentally accessible region are not
equal. Using a regularization procedure that preserves chiral symmetry and
Lorentz invariance, we find that existing data limit the integrated value of
the second moment of the asymmetry to the range at a scale of GeV. This is too small to account for the NuTeV anomaly and of the wrong
sign to enhance it.Comment: 5 pages, 4 figure
Period halving of Persistent Currents in Mesoscopic Mobius ladders
We investigate the period halving of persistent currents(PCs) of
non-interacting electrons in isolated mesoscopic M\"{o}bius ladders without
disorder, pierced by Aharonov-Bhom flux. The mechanisms of the period halving
effect depend on the parity of the number of electrons as well as on the
interchain hopping. Although the data of PCs in mesoscopic systems are
sample-specific, some simple rules are found in the canonical ensemble average,
such as all the odd harmonics of the PCs disappear, and the signals of even
harmonics are non-negative. {PACS number(s): 73.23.Ra, 73.23.-b, 68.65.-k}Comment: 6 Pages with 3 EPS figure
A Faster Implementation of Online Run-Length Burrows-Wheeler Transform
Run-length encoding Burrows-Wheeler Transformed strings, resulting in
Run-Length BWT (RLBWT), is a powerful tool for processing highly repetitive
strings. We propose a new algorithm for online RLBWT working in run-compressed
space, which runs in time and bits of space, where
is the length of input string received so far and is the number of runs
in the BWT of the reversed . We improve the state-of-the-art algorithm for
online RLBWT in terms of empirical construction time. Adopting the dynamic list
for maintaining a total order, we can replace rank queries in a dynamic wavelet
tree on a run-length compressed string by the direct comparison of labels in a
dynamic list. The empirical result for various benchmarks show the efficiency
of our algorithm, especially for highly repetitive strings.Comment: In Proc. IWOCA201
Ultrafast Magneto-Acoustics in Nickel Films
We report about the existence of magneto-acoustic pulses propagating in a
200-nm-thick ferromagnetic nickel film excited with 120 fs laser pulses. They
result from the coupling between the magnetization of the ferromagnetic film
and the longitudinal acoustic waves associated to the propagation of the
lattice deformation induced by the femtosecond laser pulses. The
magneto-acoustic pulses are detected from both the front and back sides of the
film, using the time-resolved magneto-optical Kerr technique, measuring both
the time dependent rotation and ellipticity. We show that the propagating
acoustic pulse couples efficiently to the magnetization and is strong enough to
induce a precession of the magnetization. It is due to a transient change of
the crystalline anisotropy associated to the lattice deformation. It is shown
that the results can be interpreted by combining the concepts of acoustic pulse
propagation and ultrafast magnetization dynamics.Comment: 4 pages, 3 figures, Submitted to Physical Review Letters on November
30th 201
A Temperature Analysis of High-power AlGaN/GaN HEMTs
Galliumnitride has become a strategic superior material for space, defense
and civil applications, primarily for power amplification at RF and mm-wave
frequencies. For AlGaN/GaN high electron mobility transistors (HEMT), an
outstanding performance combined together with low cost and high flexibility
can be obtained using a System-in-a-Package (SIP) approach. Since thermal
management is extremely important for these high power applications, a hybrid
integration of the HEMT onto an AlN carrier substrate is proposed. In this
study we investigate the temperature performance for AlGaN/GaN HEMTs integrated
onto AlN using flip-chip mounting. Therefore, we use thermal simulations in
combination with experimental results using micro-Raman spectroscopy and
electrical dc-analysis.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Local Duality Predictions for x ~ 1 Structure Functions
Recent data on the proton F_2 structure function in the resonance region
suggest that local quark-hadron duality works remarkably well for each of the
low-lying resonances, including the elastic, to rather low values of Q^2. We
derive model-independent relations between structure functions at x ~ 1 and
elastic electromagnetic form factors, and predict the x -> 1 behavior of
nucleon polarization asymmetries and the neutron to proton structure function
ratios from available data on nucleon electric and magnetic form factors.Comment: 10 pages, 2 figures, typos in Eq. (2) correcte
- …