7,831 research outputs found
Quantum Reciprocity Conjecture for the Non-Equilibrium Steady State
By considering the lack of history dependence in the non-equilibrium steady
state of a quantum system we are led to conjecture that in such a system, there
is a set of quantum mechanical observables whose retarded response functions
are insensitive to the arrow of time, and which consequently satisfy a quantum
analog of the Onsager reciprocity relations. Systems which satisfy this
conjecture can be described by an effective Free energy functional. We
demonstrate that the conjecture holds in a resonant level model of a multi-lead
quantum dot.Comment: References revised to take account of related work on Onsager
reciprocity in mesoscopics by Christen, and in hydrodynamics by Mclennan,
Dufty and Rub
Nitrogen hydrides in interstellar gas: Herschel/HIFI observations towards G10.6-0.4 (W31C)
The HIFI instrument on board the Herschel Space Observatory has been used to observe interstellar nitrogen hydrides along the sight-line towards
G10.6â0.4 in order to improve our understanding of the interstellar chemistry of nitrogen. We report observations of absorption in NH N = 1 â 0,
J = 2 â 1 and ortho-NH_2 1_(1,1) â 0_(0,0). We also observed ortho-NH_3 1_0 â 0_0, and 2_0 â 1_0, para-NH_3 2_1 â 1_1, and searched unsuccessfully for
NH^+. All detections show emission and absorption associated directly with the hot-core source itself as well as absorption by foreground material
over a wide range of velocities. All spectra show similar, non-saturated, absorption features, which we attribute to diffuse molecular gas. Total
column densities over the velocity range 11â54 km s^(â1) are estimated. The similar profiles suggest fairly uniform abundances relative to hydrogen,
approximately 6 Ă 10^(â9), 3 Ă 10^(â9), and 3 Ă 10^(â9) for NH, NH_2, and NH_3, respectively. These abundances are discussed with reference to models of
gas-phase and surface chemistry
Spectroscopy of drums and quantum billiards: perturbative and non-perturbative results
We develop powerful numerical and analytical techniques for the solution of
the Helmholtz equation on general domains. We prove two theorems: the first
theorem provides an exact formula for the ground state of an arbirtrary
membrane, while the second theorem generalizes this result to any excited state
of the membrane. We also develop a systematic perturbative scheme which can be
used to study the small deformations of a membrane of circular or square
shapes. We discuss several applications, obtaining numerical and analytical
results.Comment: 29 pages, 12 figures, 7 tabl
Herschel observations of EXtra-Ordinary Sources (HEXOS): Methanol as a probe of physical conditions in Orion KL
We have examined methanol emission from Orion KL withthe Herschel/HIFI instrument, and detected two methanol bands centered at 524 GHz and 1061 GHz. The 524 GHz methanol band (observed in HIFI band 1a) is dominated by the isolated ÎJ = 0, K = â4 â â3, v_t = 0 Q branch, and includes 25 E-type and 2 A-type transitions. The 1061 GHz methanol band (observed in HIFI band 4b) is dominated by the ÎJ = 0, K = 7 â 6, v_t = 0 Q branch transitions which are mostly blended. We have used the isolated E-type v_t = 0 methanol transitions to explore the physical conditions in the molecular gas. With HIFIâs high velocity resolution, the methanol emission contributed by different spatial components along the line of sight toward Orion KL (hot core, low velocity flow, and compact ridge) can be distinguished and studied separately. The isolated transitions detected in these bands cover a broad energy range (upper state energy ranging from 80 K to 900 K), which provides a unique probe of the thermal structure in each spatial component. The observations further show that the compact ridge is externally heated. These observations demonstrate the power of methanol lines as probes of the physical conditions in warm regions in close proximity to young stars
Herschel observations of EXtra-Ordinary Sources (HEXOS): The present and future of spectral surveys with Herschel/HIFI
We present initial results from the Herschel GT key program: Herschel observations of EXtra-Ordinary Sources (HEXOS) and outline the promise
and potential of spectral surveys with Herschel/HIFI. The HIFI instrument offers unprecedented sensitivity, as well as continuous spectral coverage
across the gaps imposed by the atmosphere, opening up a largely unexplored wavelength regime to high-resolution spectroscopy. We show the
spectrum of Orion KL between 480 and 560 GHz and from 1.06 to 1.115 THz. From these data, we confirm that HIFI separately measures the dust
continuum and spectrally resolves emission lines in Orion KL. Based on this capability we demonstrate that the line contribution to the broad-band
continuum in this molecule-rich source is ~20â40% below 1 THz and declines to a few percent at higher frequencies. We also tentatively identify
multiple transitions of HD^(18)O in the spectra. The first detection of this rare isotopologue in the interstellar medium suggests that HDO emission is
optically thick in the Orion hot core with HDO/H_2O ~ 0.02. We discuss the implications of this detection for the water D/H ratio in hot cores
Data processing pipeline for Herschel HIFI
Context. The HIFI instrument on the Herschel Space Observatory performed over 9100 astronomical observations, almost 900 of which were calibration observations in the course of the nearly four-year Herschel mission. The data from each observation had to be converted from raw telemetry into calibrated products and were included in the Herschel Science Archive.
Aims. The HIFI pipeline was designed to provide robust conversion from raw telemetry into calibrated data throughout all phases of the HIFI missions. Pre-launch laboratory testing was supported as were routine mission operations.
Methods. A modular software design allowed components to be easily added, removed, amended and/or extended as the understanding of the HIFI data developed during and after mission operations.
Results. The HIFI pipeline processed data from all HIFI observing modes within the Herschel automated processing environment as well as within an interactive environment. The same software can be used by the general astronomical community to reprocess any standard HIFI observation. The pipeline also recorded the consistency of processing results and provided automated quality reports. Many pipeline modules were in use since the HIFI pre-launch instrument level testing.
Conclusions. Processing in steps facilitated data analysis to discover and address instrument artefacts and uncertainties. The availability of the same pipeline components from pre-launch throughout the mission made for well-understood, tested, and stable processing. A smooth transition from one phase to the next significantly enhanced processing reliability and robustness
Herschel observations of ortho- and para-oxidaniumyl (H_2O^+) in spiral arm clouds toward Sagittarius B2(M)
H_2O^+ has been observed in its ortho- and para- states toward the massive star forming core Sgr B2(M), located close to the Galactic center. The
observations show absorption in all spiral arm clouds between the Sun and Sgr B2. The average o/p ratio of H_2O^+ in most velocity intervals
is 4.8, which corresponds to a nuclear spin temperature of 21 K. The relationship of this spin temperature to the formation temperature and current
physical temperature of the gas hosting H_2O^+ is discussed, but no firm conclusion is reached. In the velocity interval 0â60 km s^(â1), an ortho/para
ratio of below unity is found, but if this is due to an artifact of contamination by other species or real is not clear
Herschel observations of EXtra-Ordinary Sources (HEXOS): Observations of H_2O and its isotopologues towards Orion KL
We report the detection of more than 48 velocity-resolved ground rotational state transitions of H^(16)_2O, H^(18)
_2O, and ^(17)_2O â most for the first time
â in both emission and absorption toward Orion KL using Herschel/HIFI. We show that a simple fit, constrained to match the known emission
and absorption components along the line of sight, is in excellent agreement with the spectral profiles of all the water lines. Using the measured H^(18)_2O line fluxes, which are less affected by line opacity than their H^(16)_2O counterparts, and an escape probability method, the column densities
of H^(18)_2O associated with each emission component are derived. We infer total water abundances of 7.4 Ă 10^(â5), 1.0 Ă 10^(â5), and 1.6 Ă 10^(â5) for the
plateau, hot core, and extended warm gas, respectively. In the case of the plateau, this value is consistent with previous measures of the Orion-KL water abundance as well as those of other molecular outflows. In the case of the hot core and extended warm gas, these values are somewhat higher than water abundances derived for other quiescent clouds, suggesting that these regions are likely experiencing enhanced water-ice sublimation from (and reduced freeze-out onto) grain surfaces due to the warmer dust in these sources
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