53,569 research outputs found
Neutrino Oscillations and Lepton Flavor Mixing
In view of the recent announcement on non-zero neutrino mass from
Super-Kamiokande experiment, it would be very timely to investigate all the
possible scenarios on masses and mixings of light neutrinos. Recently suggested
mass matrix texture for the quark CKM mixing, which can be originated from the
family permutation symmetry and its suitable breakings, is assumed for the
neutrino mass matrix and determined by the four combinations of solar,
atmospheric and LSND neutrino data and cosmological hot dark matter bound as
input constraints. The charged-lepton mass matrix is assumed to be diagonal so
that the neutrino mixing matrix can be identified directly as the lepton flavor
mixing matrix and no CP invariance violation originates from the leptonic
sector. The results favor hierarchical patterns for the neutrino masses, which
follow from the case when either solar-atmospheric data or solar-HDM
constraints are used.Comment: Latex, 9 page
Study of 0- phase transition in hybrid superconductor-InSb nanowire quantum dot devices
Hybrid superconductor-semiconducting nanowire devices provide an ideal
platform to investigating novel intragap bound states, such as the Andreev
bound states (ABSs), Yu-Shiba-Rusinov (YSR) states, and the Majorana bound
states. The competition between Kondo correlations and superconductivity in
Josephson quantum dot (QD) devices results in two different ground states and
the occurrence of a 0- quantum phase transition. Here we report on
transport measurements on hybrid superconductor-InSb nanowire QD devices with
different device geometries. We demonstrate a realization of continuous
gate-tunable ABSs with both 0-type levels and -type levels. This allow us
to manipulate the transition between 0 and junction and explore charge
transport and spectrum in the vicinity of the quantum phase transition regime.
Furthermore, we find a coexistence of 0-type ABS and -type ABS in the same
charge state. By measuring temperature and magnetic field evolution of the
ABSs, the different natures of the two sets of ABSs are verified, being
consistent with the scenario of phase transition between the singlet and
doublet ground state. Our study provides insights into Andreev transport
properties of hybrid superconductor-QD devices and sheds light on the crossover
behavior of the subgap spectrum in the vicinity of 0- transition
Gauge/String-Gravity Duality and Froissart Bound
The gauge/string-gravity duality correspondence opened renewed hope and
possibility to address some of the fundamental and non-perturbative QCD
problems in particle physics, such as hadron spectrum and Regge behavior of the
scattering amplitude at high energies. One of the most fundamental and
long-standing problem is the high energy behavior of total cross-sections.
According to a series of exhaustive tests by the COMPETE group, (1). total
cross-sections have a universal Heisenberg behavior in energy corresponding to
the maximal energy behavior allowed by the Froissart bound, i.e., with and for all reactions,
and (2). the factorization relation among is well satisfied by experiments. I discuss the
recent interesting application of the gauge/string-gravity duality of
correspondence with a deformed background metric so as to break the conformal
symmetry that can lead to the Heisenberg behavior of rising total
cross-sections, and present some preliminary results on the high energy QCD
from Planckian scattering in and black-hole production.Comment: 10 pages, Presented to the Coral Gables Conference 2003, Launching of
BelleE\'poque in High Energy Physics and Cosmology, 17 - 21 December 2003,
Fort Lauderdale, Florid
Self-organization of charge under pressure in the organic conductor (TMTSF)2ReO4
(TMTSF)2ReO4 presents a phase coexistence between two anion orderings defined
by their wave vectors q_2=(1/2,1/2,1/2) and q_3=(0,1/2,1/2) in a wide range of
pressure (8-11kbar) and temperature. From the determination of the anisotropy
of the conductivity and the superconducting transitions in this regime we were
able to extract the texture which results from a self-organization of the
orientations of the ReO4 anions in the sample. At the lowest pressures, the
metallic parts, related to the q_3 order, form droplets elongated along the
a-axis embedded in the semiconducting matrix associated with the q_2 order.
Above 10kbar, filaments along the a-axis extend from one end of the sample to
the other nearly up to the end of the coexistence regime. A mapping of the
system into an anisotropic Ising lattice is satisfactory to analyze the data.
satisfactory to analyze the data.Comment: 7 pages, 3 figures, EPL forma
Is the Number of Giant Arcs in LCDM Consistent With Observations?
We use high-resolution N-body simulations to study the galaxy-cluster
cross-sections and the abundance of giant arcs in the CDM model.
Clusters are selected from the simulations using the friends-of-friends method,
and their cross-sections for forming giant arcs are analyzed. The background
sources are assumed to follow a uniform ellipticity distribution from 0 to 0.5
and to have an area identical to a circular source with diameter 1\arcsec. We
find that the optical depth scales as the source redshift approximately as
\tau_{1''} = 2.25 \times 10^{-6}/[1+(\zs/3.14)^{-3.42}] (0.6<\zs<7). The
amplitude is about 50% higher for an effective source diameter of 0.5\arcsec.
The optimal lens redshift for giant arcs with the length-to-width ratio ()
larger than 10 increases from 0.3 for \zs=1, to 0.5 for \zs=2, and to
0.7-0.8 for \zs>3. The optical depth is sensitive to the source redshift, in
qualitative agreement with Wambsganss et al. (2004). However, our overall
optical depth appears to be only 10% to 70% of those from previous
studies. The differences can be mostly explained by different power spectrum
normalizations () used and different ways of determining the
ratio. Finite source size and ellipticity have modest effects on the optical
depth. We also found that the number of highly magnified (with magnification
) and ``undistorted'' images (with ) is comparable to the
number of giant arcs with and . We conclude that our
predicted rate of giant arcs may be lower than the observed rate, although the
precise `discrepancy' is still unclear due to uncertainties both in theory and
observations.Comment: Revised version after the referee's reports (32 pages,13figures). The
paper has been significantly revised with many additions. The new version
includes more detailed comparisons with previous studies, including the
effects of source size and ellipticity. New discussions about the redshift
distribution of lensing clusters and the width of giant arcs have been adde
Photoemission and x-ray absorption spectroscopy study of electron-doped colossal magnetoresistance manganite: La0.7Ce0.3MnO3 film
The electronic structure of La0.7Ce0.3MnO3 (LCeMO) thin film has been
investigated using photoemission spectroscopy (PES) and x-ray absorption
spectroscopy (XAS). The Ce 3d core-level PES and XAS spectra of LCeMO are very
similar to those of CeO2, indicating that Ce ions are far from being trivalent.
A very weak 4f resonance is observed around the Ce 4d 4f absorption edge,
suggesting that the localized Ce 4f states are almost empty in the ground
state. The Mn 2p XAS spectrum reveals the existence of the Mn(2+) multiplet
feature, confirming the Mn(2+)-Mn(3+) mixed-valent states of Mn ions in LCeMO.
The measured Mn 3d PES/XAS spectra for LCeMO agrees reasonably well with the
calculated Mn 3d PDOS using the LSDA+U method. The LSDA+U calculation predicts
a half-metallic ground state for LCeMO.Comment: 7 pages, 7 figure
Diffusion-Limited Aggregation Processes with 3-Particle Elementary Reactions
A diffusion-limited aggregation process, in which clusters coalesce by means
of 3-particle reaction, A+A+A->A, is investigated. In one dimension we give a
heuristic argument that predicts logarithmic corrections to the mean-field
asymptotic behavior for the concentration of clusters of mass at time ,
, for . The total
concentration of clusters, , decays as at . We also investigate the problem with a localized steady source of
monomers and find that the steady-state concentration scales as
, , and , respectively,
for the spatial dimension equal to 1, 2, and 3. The total number of
clusters, , grows with time as , , and
for = 1, 2, and 3. Furthermore, in three dimensions we
obtain an asymptotic solution for the steady state cluster-mass distribution:
, with the scaling function
and the scaling variable .Comment: 12 pages, plain Te
Soft Pomeron and Lower-Trajectory Intercepts
We present a preliminary report on the determination of the intercepts and
couplings of the soft pomeron and of the rho/omega and f/a trajectories from
the largest data set available for all total cross sections and real parts of
the hadronic amplitudes. Factorization is reasonably satisfied by the pomeron
couplings, which allows us to make predictions on gamma gamma and gamma p total
cross sections. In addition we show that these data cannot discriminate between
fits based on a simple Regge pomeron-pole and on an asymptotic log^2s-type
behaviour, implying that the effect of unitarisation is negligible. Also we
examine the range of validity in energy of the fit, and the bounds that these
data place on the odderon and on the hard pomeron.Comment: 13 pages, LaTeX, 14 figures. Presented by K. Kang at a 4th Workshop
on Quantum Chromodynamics, June 1 - 6, 1998, The American University of
Paris, Paris, France, and at the 4th Workshop on Small-x and Diffractive
Physics, September 17 - 20, 1998, Fermi National Accelerator Laboratory,
Batavia, I
New measures of the quality and of the reliability of fits applied to forward hadronic data at t=0
We develop five new statistical measures of the quality of fits, which we
combine with the usual confidence level to determine the models which fit best
all available data for total cross sections and for the real part of the
forward hadronic amplitude.Comment: 7 pages, presented by J.R. Cudell on behalf of the COMPETE
collaboration at the 6th workshop on non-perturbative QCD, American
University of Paris, 5-9 June 200
Analytic parametrizations of the non-perturbative Pomeron and QCD-inspired models
We consider several classes of analytic parametrizations of hadronic
scattering amplitudes, and compare their predictions to all available forward
data (proton- proton, antiproton-proton, pion-proton, kaon-proton,
photon-proton, photon- photon, sigma-proton). Although these parametrizations
are very close for energy larger than 9 GeV, it turns out that they differ
markedly at low energy, where a universal Pomeron term ~(ln s)**2 enables one
to extend the fit down to 4 GeV.Comment: 11 pages, 2 tables, Presented at the 9th Blois Workshop on Elastic
and Diffractive Scattering, Pruhonice, Czech Republic, 9-15 June 200
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