18,348,258 research outputs found
Neutron star properties with relativistic equations of state
We study the properties of neutron stars adopting relativistic equations of
state of neutron star matter, calculated in the framework of the relativistic
Brueckner-Hartree-Fock approximation for electrically charge neutral neutron
star matter in beta-equilibrium. For higher densities more baryons (hyperons
etc.) are included by means of the relativistic Hartree- or Hartree-Fock
approximation. The special features of the different approximations and
compositions are discussed in detail. Besides standard neutron star properties
special emphasis is put on the limiting periods of neutron stars, for which the
Kepler criterion and gravitation-reaction instabilities are considered.
Furthermore the cooling behaviour of neutron stars is investigated, too. For
comparison we give also the outcome for some nonrelativistic equations of
state.Comment: 43 pages, 22 ps-figures, to be published in the International Journal
of Modern Physics
Cusps of Hilbert modular varieties
Motivated by a question of Hirzebruch on the possible topological types of
cusp cross-sections of Hilbert modular varieties, we give a necessary and
sufficient condition for a manifold M to be diffeomorphic to a cusp
cross-section of a Hilbert modular variety. Specialized to Hilbert modular
surfaces, this proves that every Sol 3-manifold is diffeomorphic to a cusp
cross-section of a (generalized) Hilbert modular surface. We also deduce an
obstruction to geometric bounding in this setting. Consequently, there exist
Sol 3-manifolds that cannot arise as a cusp cross-section of a 1-cusped
nonsingular Hilbert modular surface.Comment: To appear in Mathematical Proceedings Cambridge Philosophical Societ
The gamma-ray burst monitor for Lobster-ISS
Lobster-ISS is an X-ray all-sky monitor experiment selected by ESA two years
ago for a Phase A study (now almost completed) for a future flight (2009)
aboard the Columbus Exposed Payload Facility of the International Space
Station. The main instrument, based on MCP optics with Lobster-eye geometry,
has an energy passband from 0.1 to 3.5 keV, an unprecedented daily sensitivity
of 2x10^{-12} erg cm^{-2}s$^{-1}, and it is capable to scan, during each orbit,
the entire sky with an angular resolution of 4--6 arcmin. This X-ray telescope
is flanked by a Gamma Ray Burst Monitor, with the minimum requirement of
recognizing true GRBs from other transient events. In this paper we describe
the GRBM. In addition to the minimum requirement, the instrument proposed is
capable to roughly localize GRBs which occur in the Lobster FOV (162x22.5
degrees) and to significantly extend the scientific capabilities of the main
instrument for the study of GRBs and X-ray transients. The combination of the
two instruments will allow an unprecedented spectral coverage (from 0.1 up to
300/700 keV) for a sensitive study of the GRB prompt emission in the passband
where GRBs and X-Ray Flashes emit most of their energy. The low-energy spectral
band (0.1-10 keV) is of key importance for the study of the GRB environment and
the search of transient absorption and emission features from GRBs, both goals
being crucial for unveiling the GRB phenomenon. The entire energy band of
Lobster-ISS is not covered by either the Swift satellite or other GRB missions
foreseen in the next decade.Comment: 6 pages, 4 figures. Paper presented at the COSPAR 2004 General
Assembly (Paris), accepted for publication in Advances in Space Research in
June 2005 and available on-line at the Journal site
(http://www.sciencedirect.com/science/journal/02731177), section "Articles in
press
Non-existence of Ramanujan congruences in modular forms of level four
Ramanujan famously found congruences for the partition function like p(5n+4)
= 0 modulo 5. We provide a method to find all simple congruences of this type
in the coefficients of the inverse of a modular form on Gamma_{1}(4) which is
non-vanishing on the upper half plane. This is applied to answer open questions
about the (non)-existence of congruences in the generating functions for
overpartitions, crank differences, and 2-colored F-partitions.Comment: 19 page
Antimicrobials: a global alliance for optimizing their rational use in intra-abdominal infections (AGORA)
Intra-abdominal infections (IAI) are an important cause of morbidity and are frequently associated with poor prognosis, particularly in high-risk patients. The cornerstones in the management of complicated IAIs are timely effective source control with appropriate antimicrobial therapy. Empiric antimicrobial therapy is important in the management of intra-abdominal infections and must be broad enough to cover all likely organisms because inappropriate initial antimicrobial therapy is associated with poor patient outcomes and the development of bacterial resistance. The overuse of antimicrobials is widely accepted as a major driver of some emerging infections (such as C. difficile), the selection of resistant pathogens in individual patients, and for the continued development of antimicrobial resistance globally. The growing emergence of multi-drug resistant organisms and the limited development of new agents available to counteract them have caused an impending crisis with alarming implications, especially with regards to Gram-negative bacteria. An international task force from 79 different countries has joined this project by sharing a document on the rational use of antimicrobials for patients with IAIs. The project has been termed AGORA (Antimicrobials: A Global Alliance for Optimizing their Rational Use in Intra-Abdominal Infections). The authors hope that AGORA, involving many of the world's leading experts, can actively raise awareness in health workers and can improve prescribing behavior in treating IAIs
-pure homomorphisms, strong -regularity, and -injectivity
We discuss Matijevic-Roberts type theorem on strong -regularity,
-purity, and Cohen-Macaulay -injective (CMFI for short) property. Related
to this problem, we also discuss the base change problem and the openness of
loci of these properties. In particular, we define the notion of -purity of
homomorphisms using Radu-Andre homomorphisms, and prove basic properties of it.
We also discuss a strong version of strong -regularity (very strong
-regularity), and compare these two versions of strong -regularity. As a
result, strong -regularity and very strong -regularity agree for local
rings, -finite rings, and essentially finite-type algebras over an excellent
local rings. We prove the -pure base change of strong -regularity.Comment: 37 pages, updated the bibliography, and modified some error
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