4,770 research outputs found
The magnetic reorientation transition in thin ferromagnetic films treated by many-body Green's function theory
This contribution describes the reorientation of the magnetization of thin
ferromagnetic Heisenberg films as function of the temperature and/or an
external field. Working in a rotating frame allows an exact treatment of the
single-ion anisotropy when going to higher-order Green's functions. Terms due
to the exchange interaction are treated by a generalized Tyablikov (RPA)
decoupling.Comment: 9 pages, 2 figure
Herschel and ALMA Observations of Massive SZE-selected Clusters
We present new Herschel observations of four massive, Sunyaev-Zel'dovich
Effect (SZE)-selected clusters at , two of which have also
been observed with ALMA. We detect 19 Herschel/PACS counterparts to
spectroscopically confirmed cluster members, five of which have redshifts
determined via CO() and [CI]() lines. The mean [CI]/CO
line ratio is in brightness temperature units, consistent with
previous results for field samples. We do not detect significant stacked ALMA
dust continuum or spectral line emission, implying upper limits on mean
interstellar medium (H + HI) and molecular gas masses. An apparent
anticorrelation of with clustercentric radius is driven by the tight
relation between star formation rate and stellar mass. We find average specific
star formation rate log(sSFR/yr) = -10.36, which is below the SFR
correlation measured for field galaxies at similar redshifts. The fraction of
infrared-bright galaxies (IRBGs; ) per cluster
and average sSFR rise significantly with redshift. For CO detections, we find
, comparable to those of field galaxies, and gas depletion
timescales of about 2 Gyr. We use radio observations to distinguish active
galactic nuclei (AGNs) from star-forming galaxies. At least four of our 19
Herschel cluster members have , implying an AGN fraction for our PACS-selected sample.Comment: Accepted in ApJ, 46 pages, 13 figure
On the emergent Semantic Web and overlooked issues
The emergent Semantic Web, despite being in its infancy, has already received a lotof attention from academia and industry. This resulted in an abundance of prototype systems and discussion most of which are centred around the underlying infrastructure. However, when we critically review the work done to date we realise that there is little discussion with respect to the vision of the Semantic Web. In particular, there is an observed dearth of discussion on how to deliver knowledge sharing in an environment such as the Semantic Web in effective and efficient manners. There are a lot of overlooked issues, associated with agents and trust to hidden assumptions made with respect to knowledge representation and robust reasoning in a distributed environment. These issues could potentially hinder further development if not considered at the early stages of designing Semantic Web systems. In this perspectives paper, we aim to help engineers and practitioners of the Semantic Web by raising awareness of these issues
HI Narrow Self-Absorption in Dark Clouds: Correlations with Molecular Gas and Implications for Cloud Evolution and Star Formation
We present the results of a comparative study of HI narrow self-absorption
(HINSA), OH, 13CO, and C18O in five dark clouds. The HINSA follows the
distribution of the emission of the carbon monoxide isotopologues, and has a
characteristic size close to that of 13CO. This confirms that the HINSA is
produced by cold HI which is well mixed with molecular gas in well-shielded
regions. The ratio of the atomic hydrogen density to total proton density for
these sources is 5 to 27 x 10^{-4}. Using cloud temperatures and the density of
HI, we set an upper limit to the cosmic ray ionization rate of 10^{-16} s^{-1}.
Comparison of observed and modeled fractional HI abundances indicates ages for
these clouds to be 10^{6.5} to 10^{7} yr. The low values of the HI density we
have determined make it certain that the time scale for evolution from an
atomic to an almost entirely molecular phase, must be a minimum of several
million years. This clearly sets a lower limit to the overall time scale for
star formation and the lifetime of molecular clouds
Packing polymorphism of dapivirine and its impact on the performance of a dapivirine-releasing silicone elastomer vaginal ring
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The time resolution of the St. Petersburg paradox
A resolution of the St. Petersburg paradox is presented. In contrast to the
standard resolution, utility is not required. Instead, the time-average
performance of the lottery is computed. The final result can be phrased
mathematically identically to Daniel Bernoulli's resolution, which uses
logarithmic utility, but is derived using a conceptually different argument.
The advantage of the time resolution is the elimination of arbitrary utility
functions.Comment: 20 pages, 1 figur
Orbifold projection in supersymmetric QCD at N_f\leq N_c
Supersymmetric orbifold projection of N=1 SQCD with relatively small number
of flavors (not larger than the number of colors) is considered. The purpose is
to check whether orbifolding commutes with the infrared limit. On the one hand,
one considers the orbifold projection of SQCD and obtains the low-energy
description of the resulting theory. On the other hand, one starts with the
low-energy effective theory of the original SQCD, and only then perfoms
orbifolding. It is shown that at finite N_c the two low-energy theories
obtained in these ways are different. However, in the case of stabilized
run-away vacuum these two theories are shown to coincide in the large N_c
limit. In the case of quantum modified moduli space, topological solitons
carrying baryonic charges are present in the orbifolded low-energy theory.
These solitons may restore the correspondence between the two theories provided
that the soliton mass tends to zero in the large N_c limit.Comment: 10 pages; misprint corrected, reference adde
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