4,415 research outputs found
A multi-epoch spectroscopic study of the BAL quasar APM 08279+5255: I. C IV absorption variability
Broad Absorption Lines indicate gas outflows with velocities from thousands
km/s to about 0.2 the speed of light, which may be present in all quasars and
may play a major role in the evolution of the host galaxy. The variability of
absorption patterns can provide informations on changes of the density and
velocity distributions of the absorbing gas and its ionization status. We
collected 23 photometrical and spectro-photometrical observations at the 1.82m
Telescope of the Asiago Observatory since 2003, plus other 5 spectra from the
literature. We analysed the evolution in time of the equivalent width of the
broad absorption feature and two narrow absorption systems, the correlation
among them and with the R band magnitude. We performed a structure function
analysis of the equivalent width variations. We present an unprecedented
monitoring of a broad absorption line quasar based on 28 epochs in 14 years.
The shape of broad absorption feature shows a relative stability, while its
equivalent width slowly declines until it sharply increases during 2011. In the
same time the R magnitude stays almost constant until it sharply increases
during 2011. The equivalent width of the narrow absorption redwards of the
systemic redshift only shows a decline. The broad absorption behaviour suggests
changes of the ionisation status as the main cause of variability. We show for
the first time a correlation of this variability with the R band flux. The
different behaviour of the narrow absorption system might be due to
recombination time delay. The structure function of the absorption variability
has a slope comparable with typical optical variability of quasars. This is
consistent with variations of the 200 A ionising flux originating in the inner
part of the accretion disk.Comment: 10 pages, 8 figures, to appear on Astronomy & Astrophysic
Superspace formulation of general massive gauge theories and geometric interpretation of mass-dependent BRST symmetries
A superspace formulation is proposed for the osp(1,2)-covariant Lagrangian
quantization of general massive gauge theories. The superalgebra os0(1,2) is
considered as subalgebra of sl(1,2); the latter may be considered as the
algebra of generators of the conformal group in a superspace with two
anticommuting coordinates. The mass-dependent (anti)BRST symmetries of proper
solutions of the quantum master equations in the osp(1,2)-covariant formalism
are realized in that superspace as invariance under translations combined with
mass-dependent special conformal transformations. The Sp(2) symmetry - in
particular the ghost number conservation - and the "new ghost number"
conservation are realized as invariance under symplectic rotations and
dilatations, respectively. The transformations of the gauge fields - and of the
full set of necessarily required (anti)ghost and auxiliary fields - under the
superalgebra sl(1,2) are determined both for irreducible and first-stage
reducible theories with closed gauge algebra.Comment: 35 pages, AMSTEX, precision of reference
Examining the relationship between loyalty and place attachment in an urban park setting
The relationship between place attachment and loyalty has been researched in a variety of recreation and tourism contexts. This study expands upon the existing literature by examining the relationship between place attachment and behavior loyalty within an urban park setting. Specifically, the relationship between the place attachment dimensions of place identity, place dependence, and social bonding with behavioral loyalty, measured by park use frequency and proportion of use in relation to other settings. Two predictive models were tested: the first examined the influence of place attachment dimensions on loyalty as tested in previous research. The second model explored the influence of loyalty on the place attachment dimension, which had been alluded to in previous studies. The data, collected from 405 participants at eight urban parks in Manhattan Beach, California, was analyzed using structural equation modeling (SEM). Contradicting expectations, results of the study found no significant structural paths in the first model with place attachment dimensions predicting loyalty. Interestingly, the second model with behavioral loyalty predicting place attachment indicated significant relationships between all constructs. The findings of the study indicate that for an urban park setting, frequent use of specific parks contributes to stronger place attachment
High efficiency tomographic reconstruction of quantum states by quantum nondemolition measurements
We propose a high efficiency tomographic scheme to reconstruct an unknown
quantum state of the qubits by using a series of quantum nondemolition (QND)
measurements. The proposed QND measurements of the qubits are implemented by
probing the the stationary transmissions of the dispersively-coupled resonator.
It is shown that only one kind of QND measurements is sufficient to determine
all the diagonal elements of the density matrix of the detected quantum state.
The remaining non-diagonal elements of the density matrix can be determined by
other spectral measurements by beforehand transferring them to the diagonal
locations using a series of unitary operations. Compared with the pervious
tomographic reconstructions based on the usual destructively projective (DP)
measurements (wherein one kind of such measurements could only determine one
diagonal element of the density matrix), the present approach exhibits
significantly high efficiency for N-qubit (N > 1). Specifically, our generic
proposal is demonstrated by the experimental circuit-quantumelectrodynamics
(circuit-QED) systems with a few Josephson charge qubits.Comment: 9pages,4figure
Two proposals for testing quantum contextuality of continuous-variable states
We investigate the violation of non-contextuality by a class of continuous
variable states, including variations of entangled coherent states (ECS's) and
a two-mode continuous superposition of coherent states. We generalise the
Kochen-Specker (KS) inequality discussed in A. Cabello, Phys. Rev. Lett. {\bf
101}, 210401 (2008) by using effective bidimensional observables implemented
through physical operations acting on continuous variable states, in a way
similar to an approach to the falsification of Bell-CHSH inequalities put
forward recently. We test for state-independent violation of KS inequalities
under variable degrees of state entanglement and mixedness. We then demonstrate
theoretically the violation of a KS inequality for any two-mode state by using
pseudo-spin observables and a generalized quasi-probability function.Comment: 7 pages, 2 figures, RevTeX
Deep R-band counts of z~3 Lyman break galaxy candidates with the LBT
Aims. We present a deep multiwavelength imaging survey (UGR) in 3 different
fields, Q0933, Q1623, and COSMOS, for a total area of ~1500arcmin^2. The data
were obtained with the Large Binocular Camera on the Large Binocular Telescope.
Methods. To select our Lyman break galaxy (LBG) candidates, we adopted the well
established and widely used color-selection criterion (U-G vs. G-R). One of the
main advantages of our survey is that it has a wider dynamic color range for
U-dropout selection than in previous studies. This allows us to fully exploit
the depth of our R-band images, obtaining a robust sample with few interlopers.
In addition, for 2 of our fields we have spectroscopic redshift information
that is needed to better estimate the completeness of our sample and interloper
fraction. Results. Our limiting magnitudes reach 27.0(AB) in the R band
(5\sigma) and 28.6(AB) in the U band (1\sigma). This dataset was used to derive
LBG candidates at z~3. We obtained a catalog with a total of 12264 sources down
to the 50% completeness magnitude limit in the R band for each field. We find a
surface density of ~3 LBG candidates arcmin^2 down to R=25.5, where
completeness is >=95% for all 3 fields. This number is higher than the original
studies, but consistent with more recent samples.Comment: in press by A&A, full LBG candidates' catalog will be available in
electronic form at the CD
Constrained MaxLik reconstruction of multimode photon distributions
We address the reconstruction of the full photon distribution of multimode
fields generated by seeded parametric down-conversion (PDC). Our scheme is
based on on/off avalanche photodetection assisted by maximum-likelihood
(MaxLik) estimation and does not involve photon counting. We present a novel
constrained MaxLik method that incorporates the request of finite energy to
improve the rate of convergence and, in turn, the overall accuracy of the
reconstruction
Atteinte pulmonaire sévère au cours de la neurofibromatose de type 1
Type 1 neurofibromatosis (NF1) is a hereditary disease inherited as an autosomal dominant. Respiratory involvement is rare. We report the case of a woman suffering from NF1 with mutation of the corresponding gene and with respiratory involvement combining diffuse parenchymatous lesions, severe precapillary pulmonary hypertension and an enlarging, spiculated pulmonary nodule, very suspicious of malignancy, though histological examination was not possible on account of the patient\u27s poor respiratory function. There was progressive deterioration of the patient\u27s respiratory condition, leading to death, despite the introduction of oral therapy combining a phosphodiesterase 5 inhibitor and an endothelin receptor antagonist. Our case illustrates the development of multiple severe respiratory pathologies in the setting of NF1. The specific contribution of the NF1 gene mutation in the pathophysiology of these different pulmonary manifestations needs to be examined in detail
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