1,772 research outputs found
Non-commutative desingularization of determinantal varieties, I
We show that determinantal varieties defined by maximal minors of a generic
matrix have a non-commutative desingularization, in that we construct a maximal
Cohen-Macaulay module over such a variety whose endomorphism ring is
Cohen-Macaulay and has finite global dimension. In the case of the determinant
of a square matrix, this gives a non-commutative crepant resolution.Comment: 52 pages, 3 figures, all comments welcom
The Discovery of an Anomalous X-ray Pulsar in the Supernova Remnant Kes 73
We report the discovery of pulsed X-ray emission from the compact source 1E
1841-045, using data obtained with the Advanced Satellite for Cosmology and
Astrophysics. The X-ray source is located in the center of the small-diameter
supernova remnant (SNR) Kes 73 and is very likely to be the compact
stellar-remnant of the supernova which formed Kes 73. The X-rays are pulsed
with a period of ~ 11.8 s, and a sinusoidal modulation of roughly 30 %. We
interpret this modulation to be the rotation period of an embedded neutron
star, and as such would be the longest spin period for an isolated neutron star
to-date. This is especially remarkable since the surrounding SNR is very young,
at ~ 2000 yr old. We suggest that the observed characteristics of this object
are best understood within the framework of a neutron star with an enormous
dipolar magnetic field, B ~ 8x10^14 G
On the Mean-Field Limit of Bosons with Coulomb Two-Body Interaction
In the mean-field limit the dynamics of a quantum Bose gas is described by a
Hartree equation. We present a simple method for proving the convergence of the
microscopic quantum dynamics to the Hartree dynamics when the number of
particles becomes large and the strength of the two-body potential tends to 0
like the inverse of the particle number. Our method is applicable for a class
of singular interaction potentials including the Coulomb potential. We prove
and state our main result for the Heisenberg-picture dynamics of "observables",
thus avoiding the use of coherent states. Our formulation shows that the
mean-field limit is a "semi-classical" limit.Comment: Corrected typos and included an elementary proof of the Kato
smoothing estimate (Lemma 6.1
Shape Isomerism at N = 40: Discovery of a Proton Intruder in 67Co
The nuclear structure of 67Co has been investigated through 67Fe beta-decay.
The 67Fe isotopes were produced at the LISOL facility in proton-induced fission
of 238U and selected using resonant laser ionization combined with mass
separation. The application of a new correlation technique unambiguously
revealed a 496(33) ms isomeric state in 67Co at an unexpected low energy of 492
keV. A 67Co level scheme has been deduced. Proposed spin and parities suggest a
spherical (7/2-) 67Co ground state and a deformed first excited (1/2-) state at
492 keV, interpreted as a proton 1p-2h prolate intruder state.Comment: 4 pages, 5 figures, preprint submitted to Physical Review Letter
Mutation in triangulated categories and rigid Cohen-Macaulay modules
We introduce the notion of mutation of -cluster tilting subcategories in a
triangulated category with Auslander-Reiten-Serre duality. Using this idea, we
are able to obtain the complete classifications of rigid Cohen-Macaulay modules
over certain Veronese subrings.Comment: 52 pages. To appear in Invent. Mat
Cohomology Groups of Deformations of Line Bundles on Complex Tori
The cohomology groups of line bundles over complex tori (or abelian
varieties) are classically studied invariants of these spaces. In this article,
we compute the cohomology groups of line bundles over various holomorphic,
non-commutative deformations of complex tori. Our analysis interpolates between
two extreme cases. The first case is a calculation of the space of
(cohomological) theta functions for line bundles over constant, commutative
deformations. The second case is a calculation of the cohomologies of
non-commutative deformations of degree-zero line bundles.Comment: 24 pages, exposition improved, typos fixe
Investigation of the New Local Group Galaxy VV 124
We present the results of our stellar photometry and spectroscopy for the new
Local Group galaxy VV 124 (UGC 4879) obtained with the 6-m BTA telescope. The
presence of a few bright supergiants in the galaxy indicates that the current
star formation process is weak. The apparent distribution of stars with
different ages in VV 124 does not differ from the analogous distributions of
stars in irregular galaxies, but the ratio of the numbers of young and old
stars indicates that VV 124 belongs to the rare Irr/Sph type of galaxies. The
old stars (red giants) form the most extended structure, a thick disk with an
exponential decrease in the star number density to the edge. Definitely, the
young population unresolvable in images makes a great contribution to the
background emission from the central galactic regions. The presence of young
stars is also confirmed by the [O III] emission line visible in the spectra
that belongs to extensive diffuse galactic regions. The mean radial velocity of
several components (two bright supergiants, the unresolvable stellar
population, and the diffuse gas) is v_h = -70+/-15 km/s and the velocity with
which VV 124 falls into the Local Group is v_LG = -12+/-15 km/s. We confirm the
distance to the galaxy D = 1.1+/-0.1 Mpc and the metallicity of red giants
([Fe/H] = -1.37) found by Kopylov et al. (2008).VV 124 is located on the
periphery of the Local Group approximately at the same distance from M 31 and
our Galaxy and is isolated from other galaxies. The galaxy LeoA nearest to it
is 0.5 Mpc away.Comment: 10 pages, 8 figures. Accepted for publication in Astronomy Letters
(2010, Vol. 36, No. 5, pp. 309-318
Transport and cooling of singly-charged noble gas ion beams
The transport and cooling of noble gas singly-charged ion beams by means of a
Radio Frequency Quadrupole Cooler Buncher (RFQCB) have been studied at the
LIMBE low energy beam line of the GANIL facility. Ions as light as
have been cooled and stored before their extraction in bunches using as
buffer gas. Bunches characteristics have been studied as a function of the
parameters of the device. Sizeable transmissions of up to 10 have been
obtained. A detailed study of the lifetime of ions inside the buncher has been
performed giving an estimate of the charge exchange cross-section. Results of a
microscopic Monte-Carlo transport code show reasonable agreement with
experimental data.Comment: 13 figure
Gas Physics, Disk Fragmentation, and Bulge Formation in Young Galaxies
We investigate the evolution of star-forming gas-rich disks, using a 3D
chemodynamical model including a dark halo, stars, and a two-phase interstellar
medium with feedback processes from the stars. We show that galaxy evolution
proceeds along very different routes depending on whether it is the gas disk or
the stellar disk which first becomes unstable, as measured by the respective
Q-parameters. This in turn depends on the uncertain efficiency of energy
dissipation of the cold cloud component from which stars form. When the cold
gas cools efficiently and drives the instability, the galactic disk fragments
and forms a number of massive clumps of stars and gas. The clumps spiral to the
center of the galaxy in a few dynamical times and merge there to form a central
bulge component in a strong starburst. When the kinetic energy of the cold
clouds is dissipated at a lower rate, stars form from the gas in a more
quiescent mode, and an instability only sets in at later times, when the
surface density of the stellar disk has grown sufficiently high. The system
then forms a stellar bar, which channels gas into the center, evolves, and
forms a bulge whose stars are the result of a more extended star formation
history. We investigate the stability of the gas-stellar disks in both regimes,
as well as the star formation rates and element enrichment. We study the
morphology of the evolving disks, calculating spatially resolved colours from
the distribution of stars in age and metallicity, including dust absorption. We
then discuss morphological observations such as clumpy structures and chain
galaxies at high redshift as possible signatures of fragmenting, gas-rich
disks. Finally, we investigate abundance ratio distributions as a means to
distinguish the different scenarios for bulge formation.Comment: 16 pages, Latex, 14 figures, to appear in Astronomy and Astrophysics,
Version with high quality images available at
http://www.astro.unibas.ch/leute/ai.shtm
Architecture of a consent management suite and integration into IHE-based regional health information networks
<p>Abstract</p> <p>Background</p> <p>The University Hospital Heidelberg is implementing a Regional Health Information Network (RHIN) in the Rhine-Neckar-Region in order to establish a shared-care environment, which is based on established Health IT standards and in particular Integrating the Healthcare Enterprise (IHE). Similar to all other Electronic Health Record (EHR) and Personal Health Record (PHR) approaches the chosen Personal Electronic Health Record (PEHR) architecture relies on the patient's consent in order to share documents and medical data with other care delivery organizations, with the additional requirement that the German legislation explicitly demands a patients' opt-in and does not allow opt-out solutions. This creates two issues: firstly the current IHE consent profile does not address this approach properly and secondly none of the employed intra- and inter-institutional information systems, like almost all systems on the market, offers consent management solutions at all. Hence, the objective of our work is to develop and introduce an extensible architecture for creating, managing and querying patient consents in an IHE-based environment.</p> <p>Methods</p> <p>Based on the features offered by the IHE profile Basic Patient Privacy Consent (BPPC) and literature, the functionalities and components to meet the requirements of a centralized opt-in consent management solution compliant with German legislation have been analyzed. Two services have been developed and integrated into the Heidelberg PEHR.</p> <p>Results</p> <p>The standard-based Consent Management Suite consists of two services. The Consent Management Service is able to receive and store consent documents. It can receive queries concerning a dedicated patient consent, process it and return an answer. It represents a centralized policy enforcement point. The Consent Creator Service allows patients to create their consents electronically. Interfaces to a Master Patient Index (MPI) and a provider index allow to dynamically generate XACML-based policies which are stored in a CDA document to be transferred to the first service. Three workflows have to be considered to integrate the suite into the PEHR: recording the consent, publishing documents and viewing documents.</p> <p>Conclusions</p> <p>Our approach solves the consent issue when using IHE profiles for regional health information networks. It is highly interoperable due to the use of international standards and can hence be used in any other region to leverage consent issues and substantially promote the use of IHE for regional health information networks in general.</p
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