3,089 research outputs found
Areal Foliation and AVTD Behavior in T^2 Symmetric Spacetimes with Positive Cosmological Constant
We prove a global foliation result, using areal time, for T^2 symmetric
spacetimes with a positive cosmological constant. We then find a class of
solutions that exhibit AVTD behavior near the singularity.Comment: 15 pages, 0 figures, 2 references adde
Yang-Mills Flow and Uniformization Theorems
We consider a parabolic-like systems of differential equations involving
geometrical quantities to examine uniformization theorems for two- and
three-dimensional closed orientable manifolds. We find that in the
two-dimensional case there is a simple gauge theoretic flow for a connection
built from a Riemannian structure, and that the convergence of the flow to the
fixed points is consistent with the Poincare Uniformization Theorem. We
construct a similar system for the three-dimensional case. Here the connection
is built from a Riemannian geometry, an SO(3) connection and two other 1-form
fields which take their values in the SO(3) algebra. The flat connections
include the eight homogeneous geometries relevant to the three-dimensional
uniformization theorem conjectured by W. Thurston. The fixed points of the flow
include, besides the flat connections (and their local deformations), non-flat
solutions of the Yang-Mills equations. These latter "instanton" configurations
may be relevant to the fact that generic 3-manifolds do not admit one of the
homogeneous geometries, but may be decomposed into "simple 3-manifolds" which
do.Comment: 21 pages, Latex, 5 Postscript figures, uses epsf.st
Quasilinear hyperbolic Fuchsian systems and AVTD behavior in T2-symmetric vacuum spacetimes
We set up the singular initial value problem for quasilinear hyperbolic
Fuchsian systems of first order and establish an existence and uniqueness
theory for this problem with smooth data and smooth coefficients (and with even
lower regularity). We apply this theory in order to show the existence of
smooth (generally not analytic) T2-symmetric solutions to the vacuum Einstein
equations, which exhibit AVTD (asymptotically velocity term dominated) behavior
in the neighborhood of their singularities and are polarized or half-polarized.Comment: 78 page
Waveless Approximation Theories of Gravity
The analysis of a general multibody physical system governed by Einstein's
equations in quite difficult, even if numerical methods (on a computer) are
used. Some of the difficulties -- many coupled degrees of freedom, dynamic
instability -- are associated with the presence of gravitational waves. We have
developed a number of ``waveless approximation theories'' (WAT) which repress
the gravitational radiation and thereby simplify the analysis. The matter,
according to these theories, evolves dynamically. The gravitational field,
however, is determined at each time step by a set of elliptic equations with
matter sources. There is reason to believe that for many physical systems, the
WAT-generated system evolution is a very accurate approximation to that
generated by the full Einstein theory
Belimumab in Systemic Lupus Erythematosus (SLE): Evidence-To-Date and Clinical Usefulness
Systemic lupus erythematosus (SLE) is a complex autoimmune rheumatic disease with multiple presentations, whose management presents many challenges. Many disease modifying or immunosuppressive drugs have been used with limited success, especially in patients with more severe disease activity. Belimumab is the first drug to be approved specifically for the treatment of SLE in more than 50 years. By blocking the B-cell activating factor, it interferes in B-cell differentiation and survival. Here we consider the results of the clinical trials that led to its approval, as well as the post-hoc analyses, follow-up studies and the current trials.info:eu-repo/semantics/publishedVersio
Ricci flows, wormholes and critical phenomena
We study the evolution of wormhole geometries under Ricci flow using
numerical methods. Depending on values of initial data parameters, wormhole
throats either pinch off or evolve to a monotonically growing state. The
transition between these two behaviors exhibits a from of critical phenomena
reminiscent of that observed in gravitational collapse. Similar results are
obtained for initial data that describe space bubbles attached to
asymptotically flat regions. Our numerical methods are applicable to
"matter-coupled" Ricci flows derived from conformal invariance in string
theory.Comment: 8 pages, 5 figures. References added and minor changes to match
version accepted by CQG as a fast track communicatio
Psychometrics of the scale of attitudes toward physician-pharmacist collaboration: a study with medical students.
BACKGROUND: Despite the emphasis placed on interdisciplinary education and interprofessional collaboration between physicians and pharmacologists, no psychometrically sound instrument is available to measure attitudes toward collaborative relationships.
AIM: This study was designed to examine psychometrics of an instrument for measuring attitudes toward physician-pharmacist collaborative relationships for administration to students in medical and pharmacy schools and to physicians and pharmacists.
METHODS: The Scale of Attitudes Toward Physician-Pharmacist Collaboration was completed by 210 students at Jefferson Medical College. Factor analysis and correlational methods were used to examine psychometrics of the instrument.
RESULTS: Consistent with the conceptual framework of interprofessional collaboration, three underlying constructs, namely responsibility and accountability; shared authority; and interdisciplinary education emerged from the factor analysis of the instrument providing support for its construct validity. The reliability coefficient alpha for the instrument was 0.90. The instrument\u27s criterion-related validity coefficient with scores of a validated instrument (Jefferson Scale of Attitudes Toward Physician-Nurse Collaboration) was 0.70.
CONCLUSIONS: Findings provide support for the validity and reliability of the instrument for medical students. The instrument has the potential to be used for the evaluation of interdisciplinary education in medical and pharmacy schools, and for the evaluation of patient outcomes resulting from collaborative physician-pharmacist relationships
Construction of N-body initial data sets in general relativity
Given a collection of N solutions of the (3+1) vacuum Einstein constraint
equations which are asymptotically Euclidean, we show how to construct a new
solution of the constraints which is itself asymptotically Euclidean, and which
contains specified sub-regions of each of the N given solutions. This
generalizes earlier work which handled the time-symmetric case, thus providing
a construction of large classes of initial data for the many body problem in
general relativity
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