32,773 research outputs found
Radar, Insect Population Ecology, and Pest Management
Discussions included: (1) the potential role of radar in insect ecology studies and pest management; (2) the potential role of radar in correlating atmospheric phenomena with insect movement; (3) the present and future radar systems; (4) program objectives required to adapt radar to insect ecology studies and pest management; and (5) the specific action items to achieve the objectives
Anomalous Hall effect in the noncollinear antiferromagnet Mn5Si3
Metallic antiferromagnets with noncollinear orientation of magnetic moments
provide a playground for investigating spin-dependent transport properties by
analysis of the anomalous Hall effect. The intermetallic compound Mn5Si3 is an
intinerant antiferromagnet with collinear and noncollinear magnetic structures
due to Mn atoms on two inequivalent lattice sites. Here, magnetotransport
measurements on polycrystalline thin films and a single crystal are reported.
In all samples, an additional contribution to the anomalous Hall effect
attributed to the noncollinear arrangment of magnetic moments is observed.
Furthermore, an additional magnetic phase between the noncollinear and
collinear regimes above a metamagnetic transition is resolved in the single
crystal by the anomalous Hall effect.Comment: 7 pages, 4 figure
Learning about the Energy of a Hurricane System through an Estimation Epistemic Game
As part of a study into students' problem solving behaviors, we asked
upper-division physics students to solve estimation problems in clinical
interviews. We use the Resources Framework and epistemic games to describe
students' problem solving moves. We present a new epistemic game, the
"estimation epistemic game". In the estimation epistemic game, students break
the larger problem into a series of smaller, tractable problems. Within each
sub-problem, they try to remember a method for solving the problem, and use
estimation and reasoning abilities to justify their answers. We demonstrate how
a single case study student plays the game to estimate the total energy in a
hurricane. Finally, we discuss the implications of epistemic game analysis for
other estimation problems.Comment: 4 pages. Submitted to Physics Education Research Conference 201
The quadruple-lined, doubly-eclipsing system V482 Persei
We report spectroscopic and differential photometric observations of the
A-type system V482 Per that reveal it to be a rare hierarchical quadruple
system containing two eclipsing binaries. One has the previously known orbital
period of 2.4 days and a circular orbit, and the other a period of 6 days, a
slightly eccentric orbit (e = 0.11), and shallow eclipses only 2.3% deep. The
two binaries revolve around their common center of mass in a highly elongated
orbit (e = 0.85) with a period of 16.67 yr. Radial velocities are measured for
all components from our quadruple-lined spectra, and are combined with the
light curves and with measurements of times of minimum light for the 2.4 day
binary to solve for the elements of the inner and outer orbits simultaneously.
The line-of-sight inclination angles of the three orbits are similar,
suggesting they may be close to coplanar. The available observations appear to
indicate that the 6 day binary experiences significant retrograde apsidal
motion in the amount of about 60 degrees per century. We derive absolute masses
for the four stars good to better than 1.5%, along with radii with formal
errors of 1.1% and 3.5% for the 2.4 day binary and about 9% for the 6 day
binary. A comparison of these and other physical properties with current
stellar evolution models gives excellent agreement for a metallicity of [Fe/H]
= -0.15 and an age of 360 Myr.Comment: 15 pages in emulateapj format, including figures and tables. Accepted
for publication in The Astrophysical Journa
Hilbert's projective metric in quantum information theory
We introduce and apply Hilbert's projective metric in the context of quantum
information theory. The metric is induced by convex cones such as the sets of
positive, separable or PPT operators. It provides bounds on measures for
statistical distinguishability of quantum states and on the decrease of
entanglement under LOCC protocols or other cone-preserving operations. The
results are formulated in terms of general cones and base norms and lead to
contractivity bounds for quantum channels, for instance improving Ruskai's
trace-norm contraction inequality. A new duality between distinguishability
measures and base norms is provided. For two given pairs of quantum states we
show that the contraction of Hilbert's projective metric is necessary and
sufficient for the existence of a probabilistic quantum operation that maps one
pair onto the other. Inequalities between Hilbert's projective metric and the
Chernoff bound, the fidelity and various norms are proven.Comment: 32 pages including 3 appendices and 3 figures; v2: minor changes,
published versio
Spacetime structure of static solutions in Gauss-Bonnet gravity: neutral case
We study the spacetime structures of the static solutions in the
-dimensional Einstein-Gauss-Bonnet- system systematically. We
assume the Gauss-Bonnet coefficient is non-negative. The solutions
have the -dimensional Euclidean sub-manifold, which is the Einstein
manifold with the curvature and -1. We also assume , where is the curvature radius, in order for the
sourceless solution (M=0) to be defined. The general solutions are classified
into plus and minus branches. The structures of the center, horizons, infinity
and the singular point depend on the parameters , , ,
and branches complicatedly so that a variety of global structures for the
solutions are found. In the plus branch, all the solutions have the same
asymptotic structure at infinity as that in general relativity with a negative
cosmological constant. For the negative mass parameter, a new type of
singularity called the branch singularity appears at non-zero finite radius
. The divergent behavior around the singularity in Gauss-Bonnet
gravity is milder than that around the central singularity in general
relativity. In the cases the plus-branch solutions do not have any
horizon. In the case, the radius of the horizon is restricted as
) in the plus (minus)
branch. There is also the extreme black hole solution with positive mass in
spite of the lack of electromagnetic charge. We briefly discuss the effect of
the Gauss-Bonnet corrections on black hole formation in a collider and the
possibility of the violation of third law of the black hole thermodynamics.Comment: 19 pages, 11 figure
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