383 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
Quantum statistics and dynamics of nonlinear couplers with nonlinear exchange
In this paper we derive the quantum statistical and dynamical properties of
nonlinear optical couplers composed of two nonlinear waveguides operating by
the second subharmonic generation, which are coupled linearly through
evanescent waves and nonlinearly through nondegenerate optical parametric
interaction. Main attention is paid to generation and transmission of
nonclassical light, based on a discussion of squeezing phenomenon, normalized
second-order correlation function, and quasiprobability distribution functions.
Initially coherent, number and thermal states of optical beams are considered.
In particular, results are discussed in dependence on the strength of the
nonlinear coupling relatively to the linear coupling. We show that if the Fock
state enters the first waveguide and the vacuum state enters the
second waveguide, the coupler can serve as a generator of squeezed vacuum state
governed by the coupler parameters. Further, if thermal fields enter initially
the waveguides the coupler plays similar role as a microwave Josephson-junction
parametric amplifier to generate squeezed thermal light.Comment: 32 pages, 10 figure
The effective mass of atom-radiation field system and the cavity-field Wigner distribution in the presence of a homogeneous gravitational field in the Jaynes-Cummings model
The effective mass that approximately describes the effect of a classical
homogeneous gravitational field on an interacting atom-radiation field system
is determined within the framework of the Jaynes-Cummings model.
By taking into account both the atomic motion and gravitational field, a full
quantum treatment of the internal and external dynamics of the atom is
presented. By solving exactly the Schrodinger equation in the interaction
picture, the evolving state of the system is found. Influence of a classical
homogeneous gravitational field on the energy eigenvalues, the effective mass
of atom-radiation field system and the Wigner distribution of the radiation
field are studied, when initially the radiation field is prepared in a coherent
state and the two-level atom is in a coherent superposition of the excited and
ground states.Comment: 12 pages, 9 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
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
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