763 research outputs found
Phase diagram of the three-dimensional NJL model
With the exception of confinement the three-dimensional Nambu-Jona-Lasinio
(NJL_3) model incorporates many of the essential properties of QCD. We discuss
the critical properties of the model at nonzero temperature T and/or nonzero
chemical potential . We show that the universality class of the thermal
transition is that of the d=2 classical spin model with the same symmetry. We
provide evidence for the existence of a tricritical point in the
(,temperature) plane. We also discuss numerical results by Hands et al.
which showed that the system is critical for and the diquark
condensate is zero.Comment: 3 pages, To appear in the proceedings of Conference on Quarks and
Nuclear Physics (QNP 2002), Julich, Germany, 9-14 Jun 200
On the Interplay of Monopoles and Chiral Symmetry Breaking in Non-Compact Lattice QED
Non-compact lattice QED is simulated for various numbers of fermion species
ranging from 8 through 40 by the exact Hybrid Monte Carlo algorithm. Over
this range of , chiral symmetry breaking is found to be strongly
correlated with the effective monopoles in the theory. For between 8 and
16 the chiral symmetry breaking and monopole percolation transitions are second
order and coincident. Assuming powerlaw critical behavior, the correlation
length exponent for the chiral transition is identical to that of monopole
percolation. This result supports the conjecture that monopole percolation
``drives" the nontrivial chiral transition. For between 20 and 32, the
monopoles experience a first order condensation transition coincident with a
first order chiral transition. For as large as 40 both transitions are
strongly suppressed. The data at large N_f (N_f \mathrel {\mathpalette \vereq
>} 20) is interpreted in terms of a strongly interacting monopole gas-liquid
transition.Comment: Revtex file, 23 pages, hardcopy figures only
Numerical Study of the Two Color Attoworld
We consider QCD at very low temperatures and non-zero quark chemical
potential from lattice Monte Carlo simulations of the two-color theory in a
very small spatial volume (the attoscale). In this regime the quark number
rises in discrete levels in qualitative agreement with what is found
analytically at one loop on S3xS1 with radius R_S3 << 1/{\Lambda}_QCD. The
detailed level degeneracy, however, cannot be accounted for using weak coupling
arguments. At each rise in the quark number there is a corresponding spike in
the Polyakov line, also in agreement with the perturbative results. In addition
the quark number susceptibility shows a similar behaviour to the Polyakov line
and appears to be a good indicator of a confinement-deconfinement type of
transition.Comment: 18 pages, 10 figure
Mesonic Wavefunctions in the three-dimensional Gross-Neveu model
We present results from a numerical study of bound state wavefunctions in the
(2+1)-dimensional Gross-Neveu model with staggered lattice fermions at both
zero and nonzero temperature. Mesonic channels with varying quantum numbers are
identified and analysed. In the strongly coupled chirally broken phase at T=0
the wavefunctions expose effects due to varying the interaction strength more
effectively than straightforward spectroscopy. In the weakly coupled chirally
restored phase information on fermion - antifermion scattering is recovered. In
the hot chirally restored phase we find evidence for a screened interaction.
The T=0 chirally symmetric phase is most readily distinguished from the
symmetric phase at high T via the fermion dispersion relation.Comment: 18 page
Application of the Maximum Entropy Method to the (2+1)d Four-Fermion Model
We investigate spectral functions extracted using the Maximum Entropy Method
from correlators measured in lattice simulations of the (2+1)-dimensional
four-fermion model. This model is particularly interesting because it has both
a chirally broken phase with a rich spectrum of mesonic bound states and a
symmetric phase where there are only resonances. In the broken phase we study
the elementary fermion, pion, sigma and massive pseudoscalar meson; our results
confirm the Goldstone nature of the pi and permit an estimate of the meson
binding energy. We have, however, seen no signal of sigma -> pi pi decay as the
chiral limit is approached. In the symmetric phase we observe a resonance of
non-zero width in qualitative agreement with analytic expectations; in addition
the ultra-violet behaviour of the spectral functions is consistent with the
large non-perturbative anomalous dimension for fermion composite operators
expected in this model.Comment: 25 pages, 13 figure
An analysis of the content of four senior high school American history textbooks
Thesis (Ed.M.)--Boston Universit
Non-Compact QED_3 with N_f=1 and N_f=4
We present numerical results for non-compact three-dimensional QED for
numbers of flavors N_f=1 and N_f=4.In particular, we address the issue of
whether chiral symmetry is spontaneously broken in the continuum limit, and
obtain a positive answer for N_f=1, with a dimensionless condensate estimated
to be beta^2 ~= O(10^-3), implying that the critical number of
flavors N_fc>1. We also compare the N_f=1 and N_f=4 models by analysing the
transition from strong to weak coupling behaviour using an equation of state
based on a continuous phase transition. While some qualitative differences
emerge, it appears difficult to determine whether N_f=4 lies above or below
N_fc.Comment: 19 pages, 10 figure
Nurse-led implementation of ETAT plus is associated with reduced mortality in a children's hospital in Freetown, Sierra Leone
BACKGROUND: In the wake of the Ebola virus disease (EVD) epidemic in Sierra Leone, secondary care facilities faced an increase in admissions with few members of medical staff available to assess and treat patients. This led to long waiting times in hospital outpatient departments. The study was undertaken in the outpatient department of Ola During Children’s Hospital (the tertiary paediatric hospital for Sierra Leone) in the period immediately following the EVD epidemic of 2014–2015. AIMS: This retrospective analysis of operational programme data aimed to assess whether a quality-improvement approach and task-sharing between medical and nursing staff improved the quality of triage and the timeliness of care. METHODS: All staff working in the outpatient department were offered a 4-week training course, followed by on-the-job supervision and support for 6 months. Nurses who successfully completed the course were given responsibility for the initial assessment of sick patients and for prescribing and giving initial treatment. Data were collected at three points: before intervention and at 3 and 6 months after initiation of the intervention. All children presenting to the hospital for medical attention between 0800 and 1400 Monday to Friday were included. Triage assessment by the outpatient nurse was compared to that made by a clinically experienced observer, and the time taken for each child to be triaged, assessed and given initial treatment was recorded. RESULTS:Between months 0 and 6 of the intervention, detection of emergency signs by the triage nurse improved from 30% to 100%, and detection of priority signs improved from 34% to 100%. For children presenting with emergency signs, the median time between triage and full assessment improved from 57 minutes before intervention to 17 minutes at 3 months and 5 minutes at 6 months (p < 0.0005). For the same group, median time between triage and first antibiotic or antimalarial treatment improved from 220 minutes before intervention to 40 minutes at 3 months and 18 minutes at 6 months (p = 0.006). CONCLUSION: The results indicate that, with appropriate training and support, extending the emergency assessment and treatment of sick children to nursing staff in West African hospitals may improve the accuracy of triage and the time to assessment and treatment of children presenting with signs of serious illness
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