201 research outputs found
Statistics of light in Raman and Brillouin nonlinear couplers
Statistical properties of optical fields in nonlinear couplers composed of
two waveguides in which Raman or Brillouin processes (with classical pumping)
are in operation and which are mutually connected through the Stokes and/or
anti-Stokes linear interactions are investigated within the framework of
generalized superposition of coherent fields and quantum noise. Heisenberg
equations describing the couplers are solved both analytically under special
conditions and numerically in general cases. Regimes for nonclassical
properties of optical fields, such as sub-Poissonian photon-number statistics,
negative reduced moments of integrated intensity and squeezing of quadrature
fluctuations are discussed for the cases of single and compound fields. General
results are compared with those from short-length approximation.Comment: LATEX, 20 pages, 19 PostScript figure
The extended structure of the dwarf irregular galaxy Sagittarius
We present a detailed study of the stellar and HI structure of the dwarf
irregular galaxy Sagittarius. We use new deep and wide field photometry to
trace the surface brightness profile of the galaxy out to ~5.0' (corresponding
to ~1600 pc) and down to mag/arcsec, thus showing that
the stellar body of the galaxy is much more extended than previously believed,
and it is similarly (or more) extended than the overall HI distribution. The
whole major-axis profile is consistent with a pure exponential, with a scale
radius of pc. The surface density maps reveal that the
distribution of old and intermediate-age stars is smooth and remarkably
flattened out to its edges, while the associated HI has a much rounder shape,
is off-centred and presents multiple density maxima and a significant hole. No
clear sign of systemic rotation is detectable in the complex HI velocity field.
No metallicity gradient is detected in the old and intermediate age population
of the galaxy, and we confirm that this population has a much more extended
distribution than young stars (age Gyr).Comment: 11 pages, 14 figures, accepted for publication on A&A. arXiv admin
note: text overlap with arXiv:1404.169
Quantum versus classical descriptions of sub-Poissonian light generation in three-wave mixing
Sub-Poissonian light generation in the non-degenerate three-wave mixing is
studied numerically and analytically within quantum and classical approaches.
Husimi Q-functions and their classical trajectory simulations are analysed to
reveal a special regime corresponding to the time-stable sub-Poissonian
photocount statistics of the sum-frequency mode. Conditions for observation of
this regime are discussed. Theoretical predictions of the Fano factor and
explanation of the extraordinary stabilization of the sub-Poissonian photocount
behavior are obtained analytically by applying the classical trajectories.
Scaling laws for the maximum sub-Poissonian behavior are found. Noise
suppression levels in the non-degenerate vs degenerate three-wave mixing are
discussed on different time scales compared to the revival times. It is shown
that the non-degenerate conversion offers much better stabilization of the
suppressed noise in comparison to that of degenerate process.Comment: 9 pages, 12 figures, to be published in J. Optics
The extended structure of the dwarf irregular galaxies Sextans A and Sextans B. Signatures of tidal distortion in the outskirts of the Local Group
We present a detailed study of the stellar and HI structure of the dwarf
irregular galaxies SextansA and SextansB, members of the NGC3109 association.
We use newly obtained deep (r~26.5) and wide field g,r photometry to extend the
Surface Brightness (SB) profiles of the two galaxies down to mu_V~ 31.0
mag/arcsec^2. We find that both galaxies are significantly more extended than
what previously traced with surface photometry, out to ~4 kpc from their
centers along their major axis. Older stars are found to have more extended
distribution with respect to younger populations. We obtain the first estimate
of the mean metallicity for the old stars in SexB, from the color distribution
of the Red Giant Branch, =-1.6. The SB profiles show significant
changes of slope and cannot be fitted with a single Sersic model. Both galaxies
have HI discs as massive as their respective stellar components. In both cases
the HI discs display solid-body rotation with maximum amplitude of ~50 km/s
(albeit with significant uncertainty due to the poorly constrained
inclination), implying a dynamical mass ~10^{9}~M_sun, a mass-to-light ratio
M/L_V~25 and a dark-to-barionic mass ratio of ~10. The distribution of the
stellar components is more extended than the gaseous disc in both galaxies. We
find that the main, approximately round-shaped, stellar body of Sex~A is
surrounded by an elongated low-SB stellar halo that can be interpreted as a
tidal tail, similar to that found in another member of the same association
(Antlia). We discuss these, as well as other evidences of tidal disturbance, in
the framework of a past passage of the NGC3109 association close to the Milky
Way, that has been hypothesized by several authors and is also supported by the
recently discovered filamentary configuration of the association itself.Comment: Accepted for publication by A&A. PdfLateX, 16 pages, 11 figures, 2
appendice
Entanglement of bosonic modes of nonplanar molecules
Entanglement of bosonic modes of material oscillators is studied in the
context of two bilinearly coupled, nonlinear oscillators. These oscillators are
realizable in the vibrational-cum-bending motions of C-H bonds in
dihalomethanes. The bilinear coupling gives rise to invariant subspaces in the
Hilbert space of the two oscillators. The number of separable states in any
invariant subspace is one more than the dimension of the space. The dynamics of
the oscillators when the initial state belongs to an invariant subspace is
studied. In particular, the dynamics of the system when the initial state is
such that the total energy is concentrated in one of the modes is studied and
compared with the evolution of the system when the initial state is such
wherein the modes share the total energy. The dynamics of quantities such as
entropy, mean of number of quanta in the two modes and variances in the
quadratures of the two modes are studied. Possibility of generating maximally
entangled states is indicated.Comment: 21 pages, 6 figure
An HST/WFPC2 Survey of Bright Young Clusters in M31 III. Structural Parameters
Surface brightness profiles for 23 M31 star clusters were measured using
images from the Wide Field Planetary Camera 2 on the Hubble Space Telescope,
and fit to two types of models to determine the clusters' structural
properties. The clusters are primarily young (~10^8 yr) and massive (~10^4.5
solar masses), with median half-light radius 7 pc and dissolution times of a
few Gyr. The properties of the M31 clusters are comparable to those of clusters
of similar age in the Magellanic Clouds. Simulated star clusters are used to
derive a conversion from statistical measures of cluster size to half-light
radius so that the extragalactic clusters can be compared to young massive
clusters in the Milky Way. All three sets of star clusters fall approximately
on the same age-size relation. The young M31 clusters are expected to dissolve
within a few Gyr and will not survive to become old, globular clusters.
However, they do appear to follow the same fundamental plane relations as old
clusters; if confirmed with velocity dispersion measurements, this would be a
strong indication that the star cluster fundamental plane reflects universal
cluster formation conditions.Comment: AJ in press; 37 pages, 12 figure
The 1/N-expansion, quantum-classical correspondence and nonclassical states generation in dissipative higher-order anharmonic oscillators
We develop a method for the determination of thecdynamics of dissipative
quantum systems in the limit of large number of quanta N, based on the
1/N-expansion of Heidmann et al. [ Opt. Commun. 54, 189 (1985) ] and the
quantum-classical correspondence. Using this method, we find analytically the
dynamics of nonclassical states generation in the higher-order anharmonic
dissipative oscillators for an arbitrary temperature of a reservoir. We show
that the quantum correction to the classical motion increases with time
quadratically up to some maximal value, which is dependent on the degree of
nonlinearity and a damping constant, and then it decreases. Similarities and
differences with the corresponding behavior of the quantum corrections to the
classical motion in the Hamiltonian chaotic systems are discussed. We also
compare our results obtained for some limiting cases with the results obtained
by using other semiclassical tools and discuss the conditions for validity of
our approach.Comment: 15 pages, RevTEX (EPSF-style), 3 figs. Replaced with final version
(stylistic corrections
Generation of squeezed light in a nonlinear asymmetric directional coupler
We show that a nonlinear asymmetric directional coupler composed of a linear
waveguide and a nonlinear waveguide operating by nondegenerate parametric
amplification is an effective source of single-mode squeezed light. This is has
been demonstrated, under certain conditions and for specific modes, for
incident coherent beams in terms of the quasiprobability functions,
photon-number distribution and phase distribution.Comment: 19 pages, 5 figure
An HST/WFPC Survey of Bright Young Clusters in M31. II. Photometry of Less Luminous Clusters in the Fields
We report on the properties of 89 low mass star clusters located in the
vicinity of luminous young clusters (blue globulars) in the disk of M31. 82 of
the clusters are newly detected. We have determined their integrated magnitudes
and colors, based on a series of Hubble Space Telescope Wide Field/Planetary
Camera 2 exposures in blue and red (HST filters F450W and F814W). The
integrated apparent magnitudes range from F450W = 17.5 to 22.5, and the colors
indicate a wide range of ages. Stellar color-magnitude diagrams for all
clusters were obtained and those with bright enough stars were fit to
theoretical isochrones to provide age estimates. The ages range from 12 Myr to
>500 Myr. Reddenings, which average E(F450 - F814) = 0.59 with a dispersion of
0.21 magnitudes, were derived from the main sequence fitting for those
clusters. Comparison of these ages and integrated colors with single population
theoretical models with solar abundances suggests a color offset of 0.085
magnitudes at the ages tested. Estimated ages for the remaining clusters are
based on their measured colors. The age-frequency diagram shows a steep decline
of number with age, with a large decrease in number per age interval between
the youngest and the oldest clusters detected.Comment: 20 pages, 9 figure
Citronella essential oil in the control and activation of coffee plants defense response against rust and brown eye spot.
Objetivou-se avaliar o óleo essencial de citronela no controle da ferrugem e cercosporiose e na ativação de respostas de defesa em cafeeiro
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