3,795 research outputs found
Predicting Stellar Angular Diameters from , , , Photometry
Determining the physical properties of microlensing events depends on having
accurate angular sizes of the source star. Using long-baseline optical
interferometry we are able to measure the angular sizes of nearby stars with
uncertainties . We present empirically derived relations of angular
diameters that are calibrated using both a sample of dwarfs/subgiants and a
sample of giant stars. These relations are functions of five color indices in
the visible and near-infrared, and have uncertainties of 1.8-6.5% depending on
the color used. We find that a combined sample of both main-sequence and
evolved stars of A-K spectral types is well fit by a single relation for each
color considered. We find that in the colors considered, metallicity does not
play a statistically significant role in predicting stellar size, leading to a
means of predicting observed sizes of stars from color alone.Comment: 8 pages, 1 figure, accepted for publication in MNRA
An Extinction Map and Color Magnitude Diagram for the Globular Cluster NGC 3201
Differential variations of up to mag on a scale of
arcminutes across NGC 3201 are presented in the form of an extinction map. This
map, created by calculating average values for stars in small
subregions of the field with respect to a fiducial region, greatly improves the
appearance of the CMD of the cluster. We describe how we implemented this
technique in detail with our data for NGC 3201. A comparison between our map
and that of the same region extracted from the COBE/DIRBE reddening maps
published by Schlegel, Finkbeiner, & Davis (1998) (SFD) displays larger-scale
similarities between the two maps as well as smaller-scale features which show
up in our map but not in the SFD map. Several methods of determining an
zeropoint to add to our differential extinction map are presented.
Isochrone fitting proved to be the most successful one, but it produces an
average for the cluster which is smaller than previously published
values by . Finally, our results seem to support the statement
by Arce & Goodman (1999) that the SFD maps overestimate the reddening in
regions of high extinction.Comment: 19 pages, 12 figures, 1 table, accepted for publication in AJ (March
2001). Full resolution version may be obtained at
http://www.astro.lsa.umich.edu/users/kaspar/html/ngc3201.pdf (PDF) and at
http://www.astro.lsa.umich.edu/users/kaspar/html/ngc3201.ps.gz (PS
Statistical analysis for thermometric sensors test program final report
Statistical models for regression analysis of thermometric sensor
Quantum dynamics of attractive versus repulsive bosonic Josephson junctions: Bose-Hubbard and full-Hamiltonian results
The quantum dynamics of one-dimensional bosonic Josephson junctions with
attractive and repulsive interparticle interactions is studied using the
Bose-Hubbard model and by numerically-exact computations of the full many-body
Hamiltonian. A symmetry present in the Bose-Hubbard Hamiltonian dictates an
equivalence between the evolution in time of attractive and repulsive Josephson
junctions with attractive and repulsive interactions of equal magnitude. The
full many-body Hamiltonian does not possess this symmetry and consequently the
dynamics of the attractive and repulsive junctions are different.Comment: 9 pages, 2 figure
Universality of Fragmentation in the Schr\"odinger Dynamics of Bosonic Josephson Junctions
The many-body Schr\"odinger dynamics of a one-dimensional bosonic Josephson
junction is investigated for up to ten thousand bosons and long times. The
initial states are fully condensed and the interaction strength is weak. We
report on a universal fragmentation dynamics on the many-body level: systems
consisting of different numbers of particles fragment to the same value at
constant mean-field interaction strength. The phenomenon manifests itself in
observables such as the correlation functions of the system. We explain this
universal fragmentation dynamics analytically based on the Bose-Hubbard model.
We thereby show that the extent to which many-body effects become important at
later times depends crucially on the initial state. Even for arbitrarily large
particle numbers and arbitrarily weak interaction strength the dynamics is
many-body in nature and the fragmentation universal. There is no weakly
interacting limit where the Gross-Piatevskii mean-field is valid for long
times.Comment: 11 pages, 5 figure
Accurate multi-boson long-time dynamics in triple-well periodic traps
To solve the many-boson Schr\"odinger equation we utilize the
Multiconfigurational time-dependent Hartree method for bosons (MCTDHB). To be
able to attack larger systems and/or to propagate the solution for longer
times, we implement a parallel version of the MCTDHB method thereby realizing
the recently proposed [Streltsov {\it et al.} arXiv:0910.2577v1] novel idea how
to construct efficiently the result of the action of the Hamiltonian on a
bosonic state vector. We study the real-space dynamics of repulsive bosonic
systems made of N=12, 51 and 3003 bosons in triple-well periodic potentials.
The ground state of this system is three-fold fragmented. By suddenly strongly
distorting the trap potential, the system performs complex many-body quantum
dynamics. At long times it reveals a tendency to an oscillatory behavior around
a threefold fragmented state. These oscillations are strongly suppressed and
damped by quantum depletions. In spite of the richness of the observed
dynamics, the three time-adaptive orbitals of MCTDHB(M=3) are capable to
describe the many-boson quantum dynamics of the system for short and
intermediate times. For longer times, however, more self-consistent
time-adaptive orbitals are needed to correctly describe the non-equilibrium
many-body physics. The convergence of the MCTDHB() method with the number
of self-consistent time-dependent orbitals used is demonstrated.Comment: 37 pages, 7 figure
Optimal time-dependent lattice models for nonequilibrium dynamics
Lattice models are abundant in theoretical and condensed-matter physics.
Generally, lattice models contain time-independent hopping and interaction
parameters that are derived from the Wannier functions of the noninteracting
problem. Here, we present a new concept based on time-dependent Wannier
functions and the variational principle that leads to optimal time-dependent
lattice models. As an application, we use the Bose-Hubbard model with
time-dependent Wannier functions to study a quench scenario involving higher
bands. We find a separation of times scales in the dynamics and show that under
some circumstances the multi-band nonequilibrium dynamics of a quantum system
can be obtained essentially at the cost of a single-band model.Comment: 14 pages, 3 figure
Empirical study of cartograms
We report on an empirical study investigating the effectiveness and efficiency of spatial inference making with contiguous (value-by-area) cartograms, compared to informational equivalent choropleth maps, combined with graduated circles. We find significant differences in people's inference-making performance dependent on the map type. Overall, results suggest that the choropleth map with graduated circles is more effective and more efficient than the cartogram for the analysis of population census data. However, map effectiveness and efficiency also significantly depends on the inference task complexity, and more surprisingly, on the shape characteristics of the depicted enumeration units. For simple tasks, cartograms seem as effective and efficient as the more traditional mapping method. For complex inference questions, inference performance with cartograms is significantly dependent on whether regular or irregular zones are distorted. As we know still very little about the perception and cognition of cartograms, we hope to shed new light for this intriguing mapping method with this empirical study
Uji Viabilitas Benih Ketimun (Cucumis Sativus L) Hasil Perlakuan Penyerbukan Berbagai Serangga
The aim of the study was to test the cucumber seeds viability which was pollinated by different pollinators. Good seed viability is important to ensure the production. In fact successful of pollination will influence seed quality and production. This study was conducted in a completely randomized design (CRD) with one factor. Seeds used in this study were collected from previous experiment which was pollinated by different pollinators (insects, wind and human). We germinated 20 seeds per treatment. The result showed insects pollinated seeds are better than wind and human influenced. The density of the insects are not influenced the viability of the seeds. Germination rate, germination time, uniformity of seedlings is better in insect's pollinated seeds
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