159 research outputs found
An inclusion result for dagger closure in certain section rings of abelian varieties
We prove an inclusion result for graded dagger closure for primary ideals in
symmetric section rings of abelian varieties over an algebraically closed field
of arbitrary characteristic.Comment: 11 pages, v2: updated one reference, fixed 2 typos; final versio
The bass and topological stable ranks of the Bohl algebra are infinite
The Bohl algebra B is the ring of linear combinations of functions t k e λt on the real line, where k is any nonnegative integer, and λ is any complex number, with pointwise operations. We show that the Bass stable rank and the topological stable rank of B (where we use the topology of uniform convergence) are infinite
Studies on schistosomiasis. 6. A field outbreak of bilharzia in cattle
An outbreak of bilharzia (Schistosoma mattheei) infestation involving about 100 oxen on the farm Otthilie near Tolwe in northern Transvaal is described. Infestation of the cattle appears to have occurred per os from a single drinking trough. The cattle showed clinical signs and pathological lesions of both the reinfestation and the acute syndromes. The worm burdens were the highest recorded hitherto in naturally infested cattle. Severe macroscopic clay pipe stem periportal fibrosis, granulomata of the ureters and severe grey pigmentation of the lungs, are described for the first time in naturally infested cattle. There was more marked liver pigmentation than had been encountered previously in this host. A striking feature in every case was conspicuous congestion and enlargement of the ileo-cecal valve, which was dark red in colour. Treatment of affected animals with injectable trichlorphon controlled the outbreak without causing mass embolism and liver infarcts. At least 11 treatments at a dosage level of 10-12 mg/kg per treatment at 3-5 day intervals are necessary. Faecal examinations for eggs or miracidia cannot be used to assess the worm burden or the clinical state of the animal. Moreover, it is suggested that this disease may be confused with other conditions and this probably accounts for the rarity of reports of outbreaks in ruminants.The articles have been scanned in colour with a HP Scanjet 5590; 300dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format
A Simple Shell Model for Quantum Dots in a Tilted Magnetic Field
A model for quantum dots is proposed, in which the motion of a few electrons
in a three-dimensional harmonic oscillator potential under the influence of a
homogeneous magnetic field of arbitrary direction is studied. The spectrum and
the wave functions are obtained by solving the classical problem. The ground
state of the Fermi-system is obtained by minimizing the total energy with
regard to the confining frequencies. From this a dependence of the equilibrium
shape of the quantum dot on the electron number, the magnetic field parameters
and the slab thickness is found.Comment: 15 pages (Latex), 3 epsi figures, to appear in PhysRev B, 55 Nr. 20
(1997
Conservative Constraints on Dark Matter from the Fermi-LAT Isotropic Diffuse Gamma-Ray Background Spectrum
We examine the constraints on final state radiation from Weakly Interacting
Massive Particle (WIMP) dark matter candidates annihilating into various
standard model final states, as imposed by the measurement of the isotropic
diffuse gamma-ray background by the Large Area Telescope aboard the Fermi
Gamma-Ray Space Telescope. The expected isotropic diffuse signal from dark
matter annihilation has contributions from the local Milky Way (MW) as well as
from extragalactic dark matter. The signal from the MW is very insensitive to
the adopted dark matter profile of the halos, and dominates the signal from
extragalactic halos, which is sensitive to the low mass cut-off of the halo
mass function. We adopt a conservative model for both the low halo mass
survival cut-off and the substructure boost factor of the Galactic and
extragalactic components, and only consider the primary final state radiation.
This provides robust constraints which reach the thermal production
cross-section for low mass WIMPs annihilating into hadronic modes. We also
reanalyze limits from HESS observations of the Galactic Ridge region using a
conservative model for the dark matter halo profile. When combined with the
HESS constraint, the isotropic diffuse spectrum rules out all interpretations
of the PAMELA positron excess based on dark matter annihilation into two lepton
final states. Annihilation into four leptons through new intermediate states,
although constrained by the data, is not excluded.Comment: 11 pages, 5 figures. v3: minor revisions, matches version to appear
in JCA
Cosmological Non-Linearities as an Effective Fluid
The universe is smooth on large scales but very inhomogeneous on small
scales. Why is the spacetime on large scales modeled to a good approximation by
the Friedmann equations? Are we sure that small-scale non-linearities do not
induce a large backreaction? Related to this, what is the effective theory that
describes the universe on large scales? In this paper we make progress in
addressing these questions. We show that the effective theory for the
long-wavelength universe behaves as a viscous fluid coupled to gravity:
integrating out short-wavelength perturbations renormalizes the homogeneous
background and introduces dissipative dynamics into the evolution of
long-wavelength perturbations. The effective fluid has small perturbations and
is characterized by a few parameters like an equation of state, a sound speed
and a viscosity parameter. These parameters can be matched to numerical
simulations or fitted from observations. We find that the backreaction of
small-scale non-linearities is very small, being suppressed by the large
hierarchy between the scale of non-linearities and the horizon scale. The
effective pressure of the fluid is always positive and much too small to
significantly affect the background evolution. Moreover, we prove that
virialized scales decouple completely from the large-scale dynamics, at all
orders in the post-Newtonian expansion. We propose that our effective theory be
used to formulate a well-defined and controlled alternative to conventional
perturbation theory, and we discuss possible observational applications.
Finally, our way of reformulating results in second-order perturbation theory
in terms of a long-wavelength effective fluid provides the opportunity to
understand non-linear effects in a simple and physically intuitive way.Comment: 84 pages, 3 figure
All-sky search for long-duration gravitational wave transients with initial LIGO
We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10-500 s in a frequency band of 40-1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. For signals from black hole accretion disk instabilities, we set upper limits on the source rate density between 3.4×10-5 and 9.4×10-4 Mpc-3 yr-1 at 90% confidence. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves. © 2016 American Physical Society
All-sky search for long-duration gravitational wave transients with initial LIGO
We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10-500 s in a frequency band of 40-1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. For signals from black hole accretion disk instabilities, we set upper limits on the source rate density between 3.4×10-5 and 9.4×10-4 Mpc-3 yr-1 at 90% confidence. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves. © 2016 American Physical Society
Search for gravitational waves from Scorpius X-1 in the second Advanced LIGO observing run with an improved hidden Markov model
We present results from a semicoherent search for continuous gravitational waves from the low-mass x-ray binary Scorpius X-1, using a hidden Markov model (HMM) to track spin wandering. This search improves on previous HMM-based searches of LIGO data by using an improved frequency domain matched filter, the J-statistic, and by analyzing data from Advanced LIGO's second observing run. In the frequency range searched, from 60 to 650 Hz, we find no evidence of gravitational radiation. At 194.6 Hz, the most sensitive search frequency, we report an upper limit on gravitational wave strain (at 95% confidence) of h095%=3.47×10-25 when marginalizing over source inclination angle. This is the most sensitive search for Scorpius X-1, to date, that is specifically designed to be robust in the presence of spin wandering. © 2019 American Physical Society
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