27,786 research outputs found
Support of the infrared radiometer on the ST
The aim was to obtain practical experience, including observational experience, with bolometers suitable for the long wave infrared and with the filters necessary to define the spectral regions of interest. The techniques used in fabricating and testing bolometers and filters are described, and the results which were obtained to date are discussed
Quenching the XXZ spin chain: quench action approach versus generalized Gibbs ensemble
Following our previous work [PRL 113 (2014) 09020] we present here a detailed
comparison of the quench action approach and the predictions of the generalized
Gibbs ensemble, with the result that while the quench action formalism
correctly captures the steady state, the GGE does not give a correct
description of local short-distance correlation functions. We extend our
studies to include another initial state, the so-called q-dimer state. We
present important details of our construction, including new results concerning
exact overlaps for the dimer and q-dimer states, and we also give an exact
solution of the quench-action-based overlap-TBA for the q-dimer. Furthermore,
we extend our computations to include the xx spin correlations besides the zz
correlations treated previously, and give a detailed discussion of the
underlying reasons for the failure of the GGE, especially in the light of new
developments.Comment: 42 pages, 6 figures, revtex4-1 clas
The 3.1 micrometer ice band in infrared reflection nebulae
Recent observations show that infrared reflection nebulae are common phenomena in star forming regions. Extensive observations were made of two nearby infrared reflection nebulae, Orin Molecular Cloud 2 IRS1 (OMC-2/IRS1) and Cepheus A IRS6a (Cep-A/IRS6a). Mie scattering models of ice coated grains were used to study the constraints on the properties and locations of grains that could produce a feature similar to that observed in OMC-2 and Cep-A. It was concluded that scattering by ice particles alone could not be responsible for the 3.1 micron feature observed in infrared reflection nebulae
A short impossibility proof of Quantum Bit Commitment
Bit commitment protocols, whose security is based on the laws of quantum
mechanics alone, are generally held to be impossible on the basis of a
concealment-bindingness tradeoff. A strengthened and explicit impossibility
proof has been given in: G. M. D'Ariano, D. Kretschmann, D. Schlingemann, and
R. F. Werner, Phys. Rev. A 76, 032328 (2007), in the Heisenberg picture and in
a C*-algebraic framework, considering all conceivable protocols in which both
classical and quantum information are exchanged. In the present paper we
provide a new impossibility proof in the Schrodinger picture, greatly
simplifying the classification of protocols and strategies using the
mathematical formulation in terms of quantum combs, with each single-party
strategy represented by a conditional comb. We prove that assuming a stronger
notion of concealment--worst-case over the classical information
histories--allows Alice's cheat to pass also the worst-case Bob's test. The
present approach allows us to restate the concealment-bindingness tradeoff in
terms of the continuity of dilations of probabilistic quantum combs with
respect to the comb-discriminability distance.Comment: 15 pages, revtex
Element Abundance Determination in Hot Evolved Stars
The hydrogen-deficiency in extremely hot post-AGB stars of spectral class
PG1159 is probably caused by a (very) late helium-shell flash or a AGB final
thermal pulse that consumes the hydrogen envelope, exposing the usually-hidden
intershell region. Thus, the photospheric element abundances of these stars
allow us to draw conclusions about details of nuclear burning and mixing
processes in the precursor AGB stars. We compare predicted element abundances
to those determined by quantitative spectral analyses performed with advanced
non-LTE model atmospheres. A good qualitative and quantitative agreement is
found for many species (He, C, N, O, Ne, F, Si, Ar) but discrepancies for
others (P, S, Fe) point at shortcomings in stellar evolution models for AGB
stars. Almost all of the chemical trace elements in these hot stars can only be
identified in the UV spectral range. The Far Ultraviolet Spectroscopic Explorer
and the Hubble Space Telescope played a crucial role for this research.Comment: To appear in: Recent Advances in Spectroscopy: Theoretical,
Astrophysical, and Experimental Perspectives, Proceedings, Jan 28 - 31, 2009,
Kodaikanal, India (Springer
Local Hidden Variable Theories for Quantum States
While all bipartite pure entangled states violate some Bell inequality, the
relationship between entanglement and non-locality for mixed quantum states is
not well understood. We introduce a simple and efficient algorithmic approach
for the problem of constructing local hidden variable theories for quantum
states. The method is based on constructing a so-called symmetric
quasi-extension of the quantum state that gives rise to a local hidden variable
model with a certain number of settings for the observers Alice and Bob.Comment: 8 pages Revtex; v2 contains substantial changes, a strengthened main
theorem and more reference
Crossed Threshold Resummation
We show that certain general properties of threshold and joint resummations
in Drell-Yan cross sections hold as well for their crossed analogs in
semi-inclusive deep-inelastic scattering and double-inclusive leptonic
annihilation. We show that all plus-distribution corrections near threshold
show the same structure, and are determined to all logarithmic order by two
anomalous dimensions, one of which is a generalization of the D-term previously
derived in Drell-Yan. We also discuss the possibility of universality in power
corrections implied by the resummation.Comment: 8 page
Threshold resummation for the prompt-photon cross section revisited
We study the resummation of large logarithmic perturbative corrections to the
partonic cross sections relevant for the process pp->gamma X at high transverse
momentum of the photon.These corrections arise near the threshold for the
partonic reaction and are associated with soft-gluon emission. We especially
focus on the resummation effects for the contribution to the cross section
where the photon is produced in jet fragmentation. Previous calculations in
perturbation theory at fixed-order have established that this contribution is a
subdominant part of the cross section. We find, however, that it is subject to
much larger resummation effects than the direct (non-fragmentation) piece and
therefore appears to be a significant contribution in the fixed-target regime,
not much suppressed with respect to the direct part. Inclusion of threshold
resummation for the fragmentation piece leads to some improvement in
comparisons between theoretical calculations and experimental data.Comment: 12 pages, 5 figure
Infrared studies of dust grains in infrared reflection nebulae
IR reflection nebulae, regions of dust which are illuminated by nearby embedded sources, were observed in several regions of ongoing star formation. Near IR observation and theoretical modelling of the scattered light form IR reflection nebulae can provide information about the dust grain properties in star forming regions. IR reflection nebulae were modelled as plane parallel slabs assuming isotropically scattering grains. For the grain scattering properties, graphite and silicate grains were used with a power law grain size distribution. Among the free parameters of the model are the stellar luminosity and effective temperature, the optical depth of the nebula, and the extinction by foreground material. The typical results from this model are presented and discussed
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