11,722 research outputs found
Bose-Einstein Condensation in the presence of an artificial spin-orbit interaction
Bose-Einstein condensation in the presence of a synthetic spin-momentum
interaction is considered, focusing on the case where a Dirac or Rashba
potential is generated via a tripod scheme. We found that the ground states can
be either plane wave states or superpositions of them, each characterized by
their unique density distributions.Comment: 5 pages, no figure
Behavior of Li abundances in solar-analog stars II. Evidence of the connection with rotation and stellar activity
We previously attempted to ascertain why the Li I 6708 line-strengths of
Sun-like stars differ so significantly despite the superficial similarities of
stellar parameters. We carried out a comprehensive analysis of 118 solar
analogs and reported that a close connection exists between the Li abundance
A_Li and the line-broadening width (v_r+m; mainly contributed by rotational
effect), which led us to conclude that stellar rotation may be the primary
control of the surface Li content. To examine our claim in more detail, we
study whether the degree of stellar activity exhibits a similar correlation
with the Li abundance, which is expected because of the widely believed close
connection between rotation and activity. We measured the residual flux at the
line center of the strong Ca II 8542 line, r_0(8542), known to be a useful
index of stellar activity, for all sample stars using newly acquired spectra in
this near-IR region. The projected rotational velocity (v_e sin i) was
estimated by subtracting the macroturbulence contribution from v_r+m that we
had already established. A remarkable (positive) correlation was found in the
A_Li versus (vs.) r_0(8542) diagram as well as in both the r_0(8542) vs. v_e
sin i and A_Li vs. v_e sin i diagrams, as had been expected. With the
confirmation of rotation-dependent stellar activity, this clearly shows that
the surface Li abundances of these solar analogs progressively decrease as the
rotation rate decreases. Given this observational evidence, we conclude that
the depletion of surface Li in solar-type stars, probably caused by effective
envelope mixing, operates more efficiently as stellar rotation decelerates. It
may be promising to attribute the low-Li tendency of planet-host G dwarfs to
their different nature in the stellar angular momentum.Comment: 12 pages, 9 figures; accepted for publication in Astron. Astrophys
Identifying cross country skiing techniques using power meters in ski poles
Power meters are becoming a widely used tool for measuring training and
racing effort in cycling, and are now spreading also to other sports. This
means that increasing volumes of data can be collected from athletes, with the
aim of helping coaches and athletes analyse and understanding training load,
racing efforts, technique etc. In this project, we have collaborated with
Skisens AB, a company producing handles for cross country ski poles equipped
with power meters. We have conducted a pilot study in the use of machine
learning techniques on data from Skisens poles to identify which "gear" a skier
is using (double poling or gears 2-4 in skating), based only on the sensor data
from the ski poles. The dataset for this pilot study contained labelled
time-series data from three individual skiers using four different gears
recorded in varied locations and varied terrain. We systematically evaluated a
number of machine learning techniques based on neural networks with best
results obtained by a LSTM network (accuracy of 95% correctly classified
strokes), when a subset of data from all three skiers was used for training. As
expected, accuracy dropped to 78% when the model was trained on data from only
two skiers and tested on the third. To achieve better generalisation to
individuals not appearing in the training set more data is required, which is
ongoing work.Comment: Presented at the Norwegian Artificial Intelligence Symposium 201
CEDM constraints on modified sfermion universality and spontaneous CP violation
We discuss the supersymmetric CP problem that arises when the sfermion soft
mass universality is modified. We place the 3rd generation SU(5) ten-plet
sfermion masses in the weak scale in view of the naturalness. The other
sfermion masses are assumed to be universal and a TeV scale in order to weaken
the flavor changing neutral current processes and electric dipole moment (EDM)
constraints. However this modification generically induces too large up quark
chromo-EDM (CEDM) via the weak scale stop loop. In order to suppress this CEDM,
we propose certain type of flavor structure where the parameters of the
up-(s)quark sector are real whereas those of the down-(s)quark and the charged
(s)lepton sectors are complex at the GUT scale. It is shown that, in this set
up, up quark CEDM can be suppressed within the range where the current and
future experiments have their sensitivity. We briefly illustrate the simple
realization of these particular forms of the modified sfermion universality
with real up-(s)quark sector by spontaneous CP violation in E SUSY GUT with
SU(2) flavor symmetry.Comment: Hg EDM bound updated, content modified, figure added, typos
corrected, references adde
Flavor Neutrino Oscillations and Time-Energy Uncertainty Relation
We consider neutrino oscillations as non stationary phenomenon based on
Schrodinger evolution equation and mixed states of neutrinos with definite
flavors. We show that time-energy uncertainty relation plays a crucial role in
neutrino oscillations. We compare neutrino oscillations with
oscillations.Comment: A report at the 2nd Scandinavian Neutrino Workshop, SNOW 2006,
Stockholm, May 2-6, 200
Iterative solution of a Dirac equation with inverse Hamiltonian method
We solve a singe-particle Dirac equation with Woods-Saxon potentials using an
iterative method in the coordinate space representation. By maximizing the
expectation value of the inverse of the Dirac Hamiltonian, this method avoids
the variational collapse, in which an iterative solution dives into the Dirac
sea. We demonstrate that this method works efficiently, reproducing the exact
solutions of the Dirac equation.Comment: 4 pages, 3 figure
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