9,255 research outputs found
MgII Line Variability of High Luminosity Quasars
We monitored five high-luminosity quasars with lambda L_{3000A} > 10^45 erg
s^-1 at 0.4 < z < 0.6 to measure flux variability of the MgII 2798 line and
explore feasibility of reverberation mapping using MgII. Over the two year
monitoring program, imaging data were obtained with the A Noble Double-Imaging
Camera on the 1.3-m telescope at the Cerro Tololo Inter-American Observatory
(CTIO), while spectroscopic data were obtained at the same night with the R-C
spectrograph on the 1.5-m telescope at the CTIO. By performing differencial
photometry using available field stars in each quasar image, we measured
variability -- 10%-24% peak-to-peak changes and 3%-8% rms variations -- in the
B band, which includes flux changes in the rest-frame UV continuum (~2500A --
~3600A) as well as the MgII line. Utilizing photometric measurements for
spectroscopic flux calibration, we measured the MgII line flux and the
continuum flux at 3000\AA from each single-epoch spectrum. Four objects showed
MgII line flux variability with 23%-50% peak-to-peak changes and 8%-17% rms
variations over 1-1.5 year rest-frame time scales, while one object showed no
MgII flux variability within the measurement error (<5%). We also detected
4%-15% rms variations of the MgII line width for all five objects. With
synchronous observations for photometry and spectroscopy, we demonstrated the
feasibility of the MgII line reverberation mapping for high-luminosity quasars
at intermediate redshift.Comment: AJ in press, 8 pages, 8 figures edited versio
Theoretical calculations for precision polarimetry based on Mott scattering
Electron polarimeters based on Mott scattering are extensively used in
different fields in physics such as atomic, nuclear or particle physics. This
is because spin-dependent measurements gives additional information on the
physical processes under study. The main quantity that needs to be understood
in very much detail, both experimentally and theoretically, is the
spin-polarization function, so called analyzing power or Sherman function. A
detailed theoretical analysis on all the contributions to the effective
interaction potential that are relevant at the typical electron beam energies
and angles commonly used in the calibration of the experimental apparatus is
presented. The main contribution leading the theoretical error on the Sherman
function is found to correspond to radiative corrections that have been
qualitatively estimated to be below the 0.5% for the considered kinematical
conditions: unpolarized electron beams of few MeV elastically scattered from a
gold and silver targets at backward angles.Comment: Accepted versio
La huella griega en el Senado de los EE.UU.
Se estudian los referentes griegos que pueden rastrearse en la articulación de la cámara alta del poder legislativo de Estados Unidos. El número de representantes, el criterio de selección de los delegados, las competencias otorgadas al órgano senatorial y el salario estipulado permiten comprobar una profunda y deliberada selección de modelos procedentes del escenario político griegoUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Impact of the symmetry energy on the outer crust of non-accreting neutron stars
The composition and equation of state of the outer crust of non-accreting
neutron stars is computed using accurate nuclear mass tables. The main goal of
the present study is to understand the impact of the symmetry energy on the
structure of the outer crust. First, a simple "toy model" is developed to
illustrate the competition between the electronic density and the symmetry
energy. Then, realistic mass tables are used to show that models with a stiff
symmetry energy - those that generate large neutron skins for heavy nuclei -
predict a sequence of nuclei that are more neutron-rich than their softer
counterparts. This result may be phrased in the form of a correlation: the
larger the neutron skin of 208Pb, the more exotic the composition of the outer
crust.Comment: 21 pages, 8 figures, submitted to Physical Review
An Incremental Algorithm for Computing Cylindrical Algebraic Decompositions
In this paper, we propose an incremental algorithm for computing cylindrical
algebraic decompositions. The algorithm consists of two parts: computing a
complex cylindrical tree and refining this complex tree into a cylindrical tree
in real space. The incrementality comes from the first part of the algorithm,
where a complex cylindrical tree is constructed by refining a previous complex
cylindrical tree with a polynomial constraint. We have implemented our
algorithm in Maple. The experimentation shows that the proposed algorithm
outperforms existing ones for many examples taken from the literature
COMMON PROPERTY UNDER MANAGEMENT FLEXIBILITY: VALUATION, OPTIMAL EXPLOITATION, AND REGULATION
Evidence shows that fisheries need close and careful attention because it has been observed that common property fisheries might be blamed for at least two sources of inefficiency. On one hand, resource overexploitation; on the other, the "static" or "passive" management applies, as outlined in the traditional fisheries literature. This paper presents a fishery model that embraces a combination of regulatory measures, an ITQ system, and a property tax rate under management flexibility. The model allows for a common property fishery to be exploited with full economic efficiency and flexibility in contrast to the mismanagement described in the traditional literature.Resource /Energy Economics and Policy,
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