836 research outputs found
Color Deconfinement and Charmonium Production in Nuclear Collisions
In statistical QCD, color deconfinement and the properties of the quark-gluon
plasma determine the in-medium behavior of heavy quark bound states. In high
energy nuclear collisions, charmonia probe the partonic medium produced in the
early stages of the interaction. We survey the present theoretical status and
provide a critical evaluation of the charmonium production measurements in
experiments at the CERN-SPS and the BNL-RHIC.Comment: 62 pages, 86 figure
Gauge parameter dependence in the background field gauge and the construction of an invariant charge
By using the enlarged BRS transformations we control the gauge parameter
dependence of Green functions in the background field gauge. We show that it is
unavoidable -- also if we consider the local Ward identity -- to introduce the
normalization gauge parameter , which enters the Green functions of
higher orders similarly to the normalization point . The dependence of
Green functions on is governed by a further partial differential
equation. By modifying the Ward identity we are able to construct in 1-loop
order a gauge parameter independent combination of 2-point vector and
background vector functions. By explicit construction of the next orders we
show that this combination can be used to construct a gauge parameter
independent RG-invariant charge. However, it is seen that this RG-invariant
charge does not satisfy the differential equation of the normalization gauge
parameter , and, hence, is not -independent as required.Comment: 29 pages, LaTe
Staggered fermions and their improvements
Expanding upon the arguments of Sharpe, we explicitly implement the Symanzik
improvement program demonstrating the absence of order terms in the
staggered fermion action. We propose a general program to improve fermion
operators to remove corrections from their matrix elements, and
demonstrate this program for the examples of matrix elements of fermion
bilinears and . We also determine the additional operators which must be
added to improve the staggered fermion currents.Comment: 3 pages, talk presented at LATTICE'96(Improvement
Evaluating South African policies for linkage to and retention in HIV care using quasi-experimental methods
South Africa has the largest HIV-infected population in the world, with 2015 estimates of 7 million people living with HIV and 180,000 AIDS-related deaths. The South African government began scale-up of a public-sector HIV care and treatment program in 2004, and by the end of 2015, 3.4 million HIV-infected individuals were on antiretroviral therapy (ART).
When scale-up began in South Africa, ART was only available to HIV-infected individuals with CD4 counts ≤200 cells/µL or WHO clinical stage 4 disease. In 2010, treatment was extended to patients who were pregnant or who had tuberculosis and a CD4 ≤350 cells/µL, and in 2011, eligibility was extended to all patients with CD4 ≤350 cells/µL. In 2013 patients with WHO clinical stage 3 disease became eligible. In 2015, the eligibility threshold was increased to CD4 ≤500 cells/µL, and in 2016, the South African National Department of Health announced that the country would implement a “test and treat” strategy, offering free ART to all HIV-infected individuals, regardless of CD4 count.
This dissertation examines the effectiveness of several expansions and modifications to South Africa’s treatment program. In study 1, we investigated whether the 2011 extension of HIV treatment to patients with CD4 counts ≤350 cells/µL successfully increased the number of newly-eligible patients on treatment (those with CD4 counts between 201–350 cells/µL) without crowding out previously-eligible patients with more severe disease (CD4 counts ≤200 cells/µL), focusing on a network of rural clinics in KwaZulu-Natal. We found encouraging results, with newly-eligible patients (CD4 201–350) initiating treatment at a greater frequency (73.0 additional patients per month; 95% CI: 42.1; 103.9) and 47% faster than before (95% CI: 19%; 82%), while previously eligible patients (CD4 ≤200) experienced no decline in the number of patients initiating treatment or the speed of treatment uptake.
In study 2, we evaluated whether the introduction of a single-pill fixed-dose combination (FDC) treatment for ART initiators in South Africa had an impact on attrition from care compared to the previously-recommended multiple-pill regimen. We focused on an urban clinic in Johannesburg, using four different clinic attendance measures to define attrition (generally a combined measure of loss to follow-up and mortality). An intention-to-treat analysis revealed an estimated 11.3 percentage point decrease in attrition (95% CI: -22.0; -0.6) associated with the policy change, while a regression discontinuity analysis estimated an 18.0 percentage point drop in attrition (95% CI: -33.6; -2.4) associated with single-pill FDC treatment relative to multiple pills, controlling for unmeasured confounding.
In study 3, we used stratified instrumental variable analysis to examine whether the effect of FDCs on attrition varied across subsets of the patient population in the same Johannesburg clinic we evaluated in study 2. We saw larger effects among women (RD -0.25; 95% CI: -0.42; -0.09), non-anemic patients (RD -0.24; 95% CI: -0.41; -0.08), patients with early-stage (as opposed to advanced) clinical disease (RD -0.20; 95% CI: -0.32; -0.07), and those with high CD4 counts (for CD4 ≥350 cells/µL, RD -0.58; 95% CI: -1.58; 0.42). These results suggest that healthier patients saw the greatest improvement in retention in care following the switch from multiple-pill to single-pill regimens. In an era where the healthiest HIV-infected patients are now being targeted for ART treatment, FDCs can play a large role in preventing attrition from care.
These three studies depict an HIV program that has successfully grown to treat increasing numbers of patients using up-to-date strategies of care. Given the immense scale and cost of South Africa’s HIV treatment program, it is important to continue to monitor its effectiveness, especially as it introduces new treatments and strategies and adapts to the changing epidemic
Bosonization and even Grassmann variables
A new approach to bosonization in relativistic field theories and many-body
systems, based on the use of fermionic composites as integration variables in
the Berezin integral defining the partition function of the system, is tested.
The method is applied to the study of a simplified version of the BCS model.Comment: 20 pages, LaTe
Supersymmetric renormalization prescription in N = 4 super-Yang--Mills theory
Using the shadow dependent decoupled Slavnov-Taylor identities associated to
gauge invariance and supersymmetry, we discuss the renormalization of the N=4
super-Yang-Mills theory and of its coupling to gauge-invariant operators. We
specify the method for the determination of non-supersymmetric counterterms
that are needed to maintain supersymmetry
The Coupling of Chern-Simons Theory to Topological Gravity
We couple Chern-Simons gauge theory to 3-dimensional topological gravity with
the aim of investigating its quantum topological invariance. We derive the
relevant BRST rules and Batalin-Vilkovisky action. Standard BRST
transformations of the gauge field are modified by terms involving both its
anti-field and the super-ghost of topological gravity. Beyond the obvious
couplings to the metric and the gravitino, the BV action includes hitherto
neglected couplings to the super-ghost. We use this result to determine the
topological anomalies of certain higher ghost deformations of SU(N)
Chern-Simons theory, introduced years ago by Witten. In the context of
topological strings these anomalies, which generalize the familiar framing
anomaly, are expected to be cancelled by couplings of the closed string sector.
We show that such couplings are obtained by dressing the closed string field
with topological gravity observables.Comment: 39 pages, LaTex; references added, typos corrected, version to appear
in Nucl. Phys.
The spectrum of lattice QCD with staggered fermions at strong coupling
Using 4 flavors of staggered fermions at infinite gauge coupling, we compare
various analytic results for the hadron spectrum with exact Monte Carlo
simulations. Agreement with Ref. \cite{Martin_etal} is very good, at the level
of a few percent.
Our results give credence to a discrepancy between the baryon mass and the
critical chemical potential, for which baryons fill the lattice at zero
temperature and infinite gauge coupling. Independent determinations of the
latter set it at about 30% less than the baryon mass. One possible explanation
is that the nuclear attraction becomes strong at infinite gauge coupling.Comment: 11 pages, 3 figure
Remarks on the renormalization of gauge invariant operators in Yang-Mills theory
A simplified proof of a theorem by Joglekar and Lee on the renormalization of
local gauge invariant operators in Yang-Mills theory is given. It is based on
(i) general properties of the antifield-antibracket formalism; and (ii)
well-established results on the cohomology of semi-simple Lie algebras.Comment: 12 pages in LaTex, ULB-PMIF/93-0
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