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Reception analyses of science news: evaluating focus groups as a method
Bragg spectroscopy of discrete axial quasiparticle modes in a cigar-shaped degenerate Bose gas
We propose an experiment in which long wavelength discrete axial
quasiparticle modes can be imprinted in a 3D cigar-shaped Bose-Einstein
condensate by using two-photon Bragg scattering experiments, similar to the
experiment at the Weizmann Institute [J. Steinhauer {\em et al.}, Phys. Rev.
Lett. {\bf 90}, 060404 (2003)] where short wavelength axial phonons with
different number of radial modes have been observed. We provide values of the
momentum, energy and time duration of the two-photon Bragg pulse and also the
two-body interaction strength which are needed in the Bragg scattering
experiments in order to observe the long wavelength discrete axial modes. These
discrete axial modes can be observed when the system is dilute and the time
duration of the Bragg pulse is long enough.Comment: 5 pages, 3 figures, title, abstract, results changed, references
added. to appear in The European Physical Journal
S_3 Flavor Symmetry and Leptogenesis
We consider leptogenesis in a minimal
S_3 extension of the standard model with an additional Z_2 symmetry in the
leptonic sector. It is found that the CP phase appearing in the neutrino mixing
is the same as that for the CP asymmetries responsible for leptogenesis.
Because of the discrete S_3 x Z_2 flavor symmetries, the CP asymmetries are
strongly suppressed. We therefore assume that the resonant enhancement of the
CP asymmetries takes place to obtain a realistic size of baryon number
asymmetry in theuniverse. Three degenerate right-handed neutrino masses of
O(10) TeV are theoretically expected in this model.Comment: 25 pages, 3 figure
Anisotropic field dependence of the magnetic transition in Cu2Te2O5Br2
We present the results of measurements of the thermal conductivity of
Cu2Te2O5Br2, a compound where tetrahedra of Cu^{2+} ions carrying S=1/2 spins
form chains along the c-axis of the tetragonal crystal structure. The thermal
conductivity kappa was measured along both the c- and the a-direction as a
function of temperature between 3 and 300 K and in external magnetic fields H
up to 69 kOe, oriented both parallel and perpendicular to the c-axis. Distinct
features of kappa(T) were observed in the vicinity of T_N=11.4 K in zero
magnetic field. These features are unaltered in external fields which are
parallel to the c-axis, but are more pronounced when a field is applied
perpendicularly to the c-axis. The transition temperature increases upon
enhancing the external field, but only if the field is oriented along the
a-axis.Comment: 5 pages, 3 figure
Dirac Spinors and Flavor Oscillations
In the standard treatment of particle oscillations the mass eigenstates are
implicitly assumed to be scalars and, consequently, the spinorial form of
neutrino wave functions is not included in the calculations. To analyze this
additional effect, we discuss the oscillation probability formula obtained by
using the Dirac equation as evolution equation for the neutrino mass
eigenstates. The initial localization of the spinor state also implies an
interference between positive and negative energy components of mass eigenstate
wave packets which modifies the standard oscillation probability.Comment: 14 pages, 1 figure, AMS-Te
One-step generation of high-quality squeezed and EPR states in cavity QED
We show how to generate bilinear (quadratic) Hamiltonians in cavity quantum
electrodynamics (QED) through the interaction of a single driven three-level
atom with two (one) cavity modes. With this scheme it is possible to generate
one-mode mesoscopic squeezed superpositions, two-mode entanglements, and
two-mode squeezed vacuum states (such the original EPR state), without the need
for Ramsey zones and external parametric amplification. The degree of squeezing
achieved is up to 99% with currently feasible experimental parameters and the
errors due to dissipative mechanisms become practically negligible
Quantifying bid-ask spreads in the Chinese stock market using limit-order book data: Intraday pattern, probability distribution, long memory, and multifractal nature
The statistical properties of the bid-ask spread of a frequently traded
Chinese stock listed on the Shenzhen Stock Exchange are investigated using the
limit-order book data. Three different definitions of spread are considered
based on the time right before transactions, the time whenever the highest
buying price or the lowest selling price changes, and a fixed time interval.
The results are qualitatively similar no matter linear prices or logarithmic
prices are used. The average spread exhibits evident intraday patterns
consisting of a big L-shape in morning transactions and a small L-shape in the
afternoon. The distributions of the spread with different definitions decay as
power laws. The tail exponents of spreads at transaction level are well within
the interval and that of average spreads are well in line with the
inverse cubic law for different time intervals. Based on the detrended
fluctuation analysis, we found the evidence of long memory in the bid-ask
spread time series for all three definitions, even after the removal of the
intraday pattern. Using the classical box-counting approach for multifractal
analysis, we show that the time series of bid-ask spread does not possess
multifractal nature.Comment: 8 EPJ pages including 7 eps figure
Hard scattering and jets--from p-p collisions in the 1970's to Au+Au collisions at RHIC
Hard scattering in p-p collisions, discovered at the CERN ISR in 1972 by the
method of leading particles, proved that the partons of Deeply Inelastic
Scattering strongly interacted with each other. Further ISR measurements
utilizing inclusive single or pairs of hadrons established that high pT
particles are produced from states with two roughly back-to-back jets which are
the result of scattering of constituents of the nucleons as described by
Quantum Chromodynamics (QCD), which was developed during the course of these
measurements. These techniques, which are the only practical method to study
hard-scattering and jet phenomena in Au+Au central collisions, are reviewed,
with application to measurements at RHIC.Comment: 4 pages, 5 figures, Proceedings of Hard Probes 2004, International
Conference on Hard and Electromagnetic Probes of High Energy Nuclear
Collisions, Nov 4-10, 2004, to appear in EPJ
Leading-particle suppression in high energy nucleus-nucleus collisions
Parton energy loss effects in heavy-ion collisions are studied with the Monte
Carlo program PQM (Parton Quenching Model) constructed using the BDMPS
quenching weights and a realistic collision geometry. The merit of the approach
is that it contains only one free parameter that is tuned to the high-pt
nuclear modification factor measured in central Au-Au collisions at sqrt{s_NN}
= 200 GeV. Once tuned, the model is coherently applied to all the high-pt
observables at 200 GeV: the centrality evolution of the nuclear modification
factor, the suppression of the away-side jet-like correlations, and the
azimuthal anisotropies for these observables. Predictions for the
leading-particle suppression at nucleon-nucleon centre-of-mass energies of 62.4
and 5500 GeV are calculated. The limits of the eikonal approximation in the
BDMPS approach, when applied to finite-energy partons, are discussed.Comment: 28 pages, 14 figures, final version, accepted by Eur. Phys. J.
DNA Renaturation at the Water-Phenol Interface
We study DNA adsorption and renaturation in a water-phenol two-phase system,
with or without shaking. In very dilute solutions, single-stranded DNA is
adsorbed at the interface in a salt-dependent manner. At high salt
concentrations the adsorption is irreversible. The adsorption of the
single-stranded DNA is specific to phenol and relies on stacking and hydrogen
bonding. We establish the interfacial nature of a DNA renaturation at a high
salt concentration. In the absence of shaking, this reaction involves an
efficient surface diffusion of the single-stranded DNA chains. In the presence
of a vigorous shaking, the bimolecular rate of the reaction exceeds the
Smoluchowski limit for a three-dimensional diffusion-controlled reaction. DNA
renaturation in these conditions is known as the Phenol Emulsion Reassociation
Technique or PERT. Our results establish the interfacial nature of PERT. A
comparison of this interfacial reaction with other approaches shows that PERT
is the most efficient technique and reveals similarities between PERT and the
renaturation performed by single-stranded nucleic acid binding proteins. Our
results lead to a better understanding of the partitioning of nucleic acids in
two-phase systems, and should help design improved extraction procedures for
damaged nucleic acids. We present arguments in favor of a role of phenol and
water-phenol interface in prebiotic chemistry. The most efficient renaturation
reactions (in the presence of condensing agents or with PERT) occur in
heterogeneous systems. This reveals the limitations of homogeneous approaches
to the biochemistry of nucleic acids. We propose a heterogeneous approach to
overcome the limitations of the homogeneous viewpoint
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