910 research outputs found
The 3.3 micron emission feature: Map of the galactic disk, 10 deg less than 1 less than 35 deg, - 6 deg less than b less than 6 deg
The 3.3 micron aromatic feature has been detected in the diffuse galactic emission with the AROME balloon-borne instrument. The results are presented in the form of an map of the 3.3 micron feature's intensity. The AROME instrument consists in a Cassegrain telescope with wobbling secondary mirrors and a liquid/solid nitrogen cooled photometer. The instrumental output is modified by the impulse response of the system. So the galactic surface brightness was restored in Fourier space by an inverse optimal filtering. The map of the feature's intensity is presented for a region of galactic coordinates. All the known H II giant molecular cloud complexes are visible in the 3.3 micron feature emission showing a good correlation with the infrared dust emission
Correlation functions of the one-dimensional attractive Bose gas
The zero-temperature correlation functions of the one-dimensional attractive
Bose gas with delta-function interaction are calculated analytically for any
value of the interaction parameter and number of particles, directly from the
integrability of the model. We point out a number of interesting features,
including zero recoil energy for large number of particles, analogous to a
M\"ossbauer effect.Comment: 4 pages, 2 figure
Deformed strings in the Heisenberg model
We investigate solutions to the Bethe equations for the isotropic S = 1/2
Heisenberg chain involving complex, string-like rapidity configurations of
arbitrary length. Going beyond the traditional string hypothesis of undeformed
strings, we describe a general procedure to construct eigenstates including
strings with generic deformations, discuss general features of these solutions,
and provide a number of explicit examples including complete solutions for all
wavefunctions of short chains. We finally investigate some singular cases and
show from simple symmetry arguments that their contribution to zero-temperature
correlation functions vanishes.Comment: 34 pages, 13 figure
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Shocks and PDRs in an intermediate mass star forming globule: the case of IC1396N
The dark globule IC1396N is a typical example of a star formation process induced by radiation driven implosion due to the strong UV field from a nearby O6 star. The IRAS source embedded in the globule and its associated molecular outflow have been observed with the Long Wavelength Spectrometer (LWS) on ISO revealing an extremely rich spectrum including: CO rotational lines from J=14-13 up to J=28-27, rotational lines from ortho-H2O, OH lines involving the first four rotational levels of both ladders, atomic (OI 63ÎĽm, OI 145ÎĽm) and ionic (CII 157ÎĽm, OIII 52ÎĽm, OIII 88ÎĽm) lines. A complex picture arises, where an externally illuminated PDR coexists with strong C-shocks within IC1396N and whose origin is not clear
The two-boundary sine-Gordon model
We study in this paper the ground state energy of a free bosonic theory on a
finite interval of length with either a pair of sine-Gordon type or a pair
of Kondo type interactions at each boundary. This problem has potential
applications in condensed matter (current through superconductor-Luttinger
liquid-superconductor junctions) as well as in open string theory (tachyon
condensation). While the application of Bethe ansatz techniques to this problem
is in principle well known, considerable technical difficulties are
encountered. These difficulties arise mainly from the way the bare couplings
are encoded in the reflection matrices, and require complex analytic
continuations, which we carry out in detail in a few cases.Comment: 34 pages (revtex), 8 figure
Deuterium and N fractionation in NH during the formation of a Sun-like star
Although chemical models predict that the deuterium fractionation in
NH is a good evolutionary tracer in the star formation process, the
fractionation of nitrogen is still a poorly understood process. Recent models
have questioned the similar evolutionary trend expected for the two
fractionation mechanisms in NH, based on a classical scenario in which
ion-neutral reactions occurring in cold gas should have caused an enhancement
of the abundance of ND, NNH, and NNH. In the
framework of the ASAI IRAM-30m large program, we have investigated the
fractionation of deuterium and N in NH in the best known
representatives of the different evolutionary stages of the Sun-like star
formation process. The goal is to ultimately confirm (or deny) the classical
"ion-neutral reactions" scenario that predicts a similar trend for D and
N fractionation. We do not find any evolutionary trend of the
N/N ratio from both the NNH and NNH
isotopologues. Therefore, our findings confirm that, during the formation of a
Sun-like star, the core evolution is irrelevant in the fractionation of
N. The independence of the N/N ratio with time, found also
in high-mass star-forming cores, indicates that the enrichment in N
revealed in comets and protoplanetary disks is unlikely to happen at core
scales. Nevertheless, we have firmly confirmed the evolutionary trend expected
for the H/D ratio, with the NH/ND ratio decreasing before the
pre-stellar core phase, and increasing monotonically during the protostellar
phase. We have also confirmed clearly that the two fractionation mechanisms are
not related.Comment: 9 pages, 2 figures, accepted for publication in MNRA
Computation of dynamical correlation functions of Heisenberg chains in a field
We compute the momentum- and frequency-dependent longitudinal spin structure
factor for the one-dimensional spin-1/2 Heisenberg spin chain in a
magnetic field, using exact determinant representations for form factors on the
lattice. Multiparticle contributions are computed numerically throughout the
Brillouin zone, yielding saturation of the sum rule to high precision.Comment: 4 pages, 14 figure
A Direct Measurement of the Total Gas Column Density in Orion KL
The large number of high-J lines of C^(18)O available via the Herschel Space Observatory provide an unprecedented ability to model the total CO column density in hot cores. Using the emission from all the observed lines (up to J = 15-14), we sum the column densities in each individual level to obtain the total column after correcting for the population in the unobserved states. With additional knowledge of source size, V_(LSR), and line width, and both local thermodynamic equilibrium (LTE) and non-LTE modeling, we have determined the total C^(18)O column densities in the Extended Ridge, Outflow/Plateau, Compact Ridge, and Hot Core components of Orion KL to be 1.4 × 10^(16) cm^(–2), 3.5 × 10^(16) cm^(–2), 2.2 × 10^(16) cm^(–2), and 6.2 × 10^(16) cm^(–2), respectively. We also find that the C^(18)O/C^(17)O abundance ratio varies from 1.7 in the Outflow/Plateau, 2.3 in the Extended Ridge, 3.0 in the Hot Core, and to 4.1 in the Compact Ridge. This is in agreement with models in which regions with higher ultraviolet radiation fields selectively dissociate C^(17)O, although care must be taken when interpreting these numbers due to the size of the uncertainties in the C^(18)O/C^(17)O abundance ratio
Using the average spectrum method to extract dynamics from quantum Monte Carlo simulations
We apply the Average Spectrum Method to the problem of getting the excitation
spectrum from imaginary-time quantum Monte Carlo simulations. We show that with
high quality QMC data this method reproduces the dominant spectral features
very well. It is also capable of giving information on the spectrum in regions
dominated by the many-particle continuum of excitations.Comment: v2: Major revision. Title and abstract as well as the focus of the
paper have been changed. Added a figure about the dynamics of 1D Heisenberg
chai
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