3,617 research outputs found
From quantum stochastic differential equations to Gisin-Percival state diffusion
Starting from the quantum stochastic differential equations of Hudson and
Parthasarathy (Comm. Math. Phys. 93, 301 (1984)) and exploiting the
Wiener-Ito-Segal isomorphism between the Boson Fock reservoir space
and
the Hilbert space , where is the Wiener probability measure of
a complex -dimensional vector-valued standard Brownian motion
, we derive a non-linear stochastic Schrodinger
equation describing a classical diffusion of states of a quantum system, driven
by the Brownian motion . Changing this Brownian motion by an
appropriate Girsanov transformation, we arrive at the Gisin-Percival state
diffusion equation (J. Phys. A, 167, 315 (1992)). This approach also yields an
explicit solution of the Gisin-Percival equation, in terms of the
Hudson-Parthasarathy unitary process and a radomized Weyl displacement process.
Irreversible dynamics of system density operators described by the well-known
Gorini-Kossakowski-Sudarshan-Lindblad master equation is unraveled by
coarse-graining over the Gisin-Percival quantum state trajectories.Comment: 28 pages, one pdf figure. An error in the multiplying factor in Eq.
(102) corrected. To appear in Journal of Mathematical Physic
High resolution spectroscopy of the high velocity hot post-AGB star LS III +52 24 (IRAS 22023+5249)
The first high-resolution (R~50,000) optical spectrum of the B-type star, LS
III +52 24, identified as the optical counterpart of the hot post-AGB candidate
IRAS 22023+5249 (I22023) is presented. We report the detailed identifications
of the observed absorption and emission features in the full wavelength range
(4290-9015 A) as well as the atmospheric parameters and photospheric abundances
(under the Local Thermodinamic Equilibrium approximation) for the first time.
The nebular parameters (Te, Ne) are also derived. We estimate Teff=24,000 K,
log g=3.0, xi=7 kms-1 and the derived abundances indicate a slightly
metal-deficient evolved star with C/O<1. The observed P-Cygni profiles of
hydrogen and helium clearly indicate on-going post-AGB mass loss. The presence
of [N II] and [S II] lines and the non-detection of [O III] indicate that
photoionisation has just started. The observed spectral features, large
heliocentric radial velocity, atmospheric parameters, and chemical composition
indicate that I22023 is an evolved post-AGB star belonging to the old disk
population. The derived nebular parameters (Te=7000 K, Ne=1.2x104 cm-3) also
suggest that I22023 may be evolving into a compact, young low-excitation
Planetary Nebula. Our optical spectroscopic analysis together with the recent
Spitzer detection of double-dust chemistry (the simultaneous presence of
carbonaceous molecules and amorphous silicates) in I22023 and other B-type
post-AGB candidates may point to a binary system with a dusty disk as the
stellar origin common to the hot post-AGB stars with O-rich central stars.Comment: Accepted for publication in MNRAS (22 pages, 4 figures, and 8
tables). arXiv admin note: substantial text overlap with arXiv:0707.059
Spontaneous Time Asymmetry due to Horizon
We show that quantized matter fields in the presence of background metrics
with Horizon exhibit spontaneous time asymmetry. All quantized matter fields
have to vanish at the horizon. Some phenemenological applications of this in
the context of black holes and early universe are considered.Comment: 4 pages, Revte
An Infrared Camera for Leuschner Observatory and the Berkeley Undergraduate Astronomy Lab
We describe the design, fabrication, and operation of an infrared camera
which is in use at the 30-inch telescope of the Leuschner Observatory. The
camera is based on a Rockwell PICNIC 256 x 256 pixel HgCdTe array, which is
sensitive from 0.9-2.5 micron. The primary purpose of this telescope is for
undergraduate instruction. The cost of the camera has been minimized by using
commercial parts whereever practical. The camera optics are based on a modified
Offner relay which forms a cold pupil where stray thermal radiation from the
telescope is baffled. A cold, six-position filter wheel is driven by a
cryogenic stepper motor, thus avoiding any mechanical feed throughs. The array
control and readout electronics are based on standard PC cards; the only custom
component is a simple interface card which buffers the clocks and amplifies the
analog signals from the array.Comment: 13 pages, 17 figures. Submitted to Publications of the Astronomical
Society of the Pacific: 2001 Jan 10, Accepted 2001 Jan 1
Spectroscopy of the post-AGB star HD 101584(IRAS 11385-5517)
From an analysis of the spectrum (4000\AA to 8800\AA) of HD~101584 it is
found that most of the neutral and single ionized metallic lines are in
emission. The forbidden emission lines of [OI] 6300\AA and 6363\AA and [CI]
8727\AA are detected, which indicate the presence of a very low excitation
nebula. The H, FeII 6383\AA, NaI D, D lines and the CaII IR
triplet lines show P-Cygni profiles indicating a mass outflow. The H
line shows many velocity components in the profile. The FeII 6383\AA also has
almost the same line profile as the H line indicating that they are
formed in the same region. From the spectrum synthesis analysis we find the
atmospheric parameters to be T=8500K, log g=1.5,
V=13km~s and [Fe/H]=0.0. From an analysis of the absorption
lines the photospheric abundances of some of the elements are derived. Carbon
and nitrogen are found to be overabundant. From the analysis of Fe emission
lines we derived T=6100K200 for the emission line region.Comment: To appear in A&A, 15 pages, 11 figure
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