402 research outputs found
Monte Carlo Hamiltonian
We suggest how to construct an effective low energy Hamiltonian via Monte
Carlo starting from a given action. We test it by computing thermodynamical
observables like average energy and specific heat for simple quantum systems.Comment: Contribution to Lattice'99 (Theoretical developments) Text (LaTeX
file) + 2 figures (ps files
Why Use a Hamilton Approach in QCD?
We discuss in the Hamiltonian frame work. We treat finite density
in the strong coupling regime. We present a parton-model inspired
regularisation scheme to treat the spectrum (-angles) and distribution
functions in . We suggest a Monte Carlo method to construct
low-dimensionasl effective Hamiltonians. Finally, we discuss improvement in
Hamiltonian .Comment: Proceedings of Hadrons and Strings, invited talk given by H.
Kr\"{o}ger; Text (LaTeX file), 3 Figures (ps file
Monte Carlo Hamiltonian from Stochastic Basis
In order to extend the recently proposed Monte Carlo Hamiltonian to many-body
systems, we suggest to concept of a stochastic basis. We apply it to the chain
of coupled anharmonic oscillators. We compute the spectrum of excited
states in a finite energy window and thermodynamical observables free energy,
average energy, entropy and specific heat in a finite temperature window.
Comparing the results of the Monte Carlo Hamiltonian with standard Lagrangian
lattice calculations, we find good agreement. However, the Monte Carlo
Hamiltonian results show less fluctuations under variation of temperature.Comment: revised version, new figures. Text (LaTeX), 4 Figs. (eps), style fil
The association between distal findings and proximal colorectal neoplasia: a systematic review and meta-analysis
Objectives:
Whether screening participants with distal hyperplastic polyps (HPs) detected by flexible sigmoidoscopy (FS) should be followed by subsequent colonoscopy is controversial. We evaluated the association between distal HPs and proximal neoplasia (PN)/advanced proximal neoplasia (APN) in asymptomatic, average-risk patients.
Methods:
We searched Ovid Medline, EMBASE, and the Cochrane Library from inception to 30 June 2016 and included all screening studies that examined the relationship between different distal findings and PN/APN. Data were independently extracted by two reviewers with disagreements resolved by a third reviewer. We pooled absolute risks and odds ratios (ORs) with a random effects meta-analysis. Seven subgroup analyses were performed according to study characteristics. Heterogeneity was characterized with theI2 statistics.
Results:
We analyzed 28 studies (104,961 subjects). When compared with normal distal findings, distal HP was not associated with PN (OR=1.16, 95% confidence interval (CI)=0.89–1.51,P=0.14,I2=40%) or APN (OR=1.09, 95% CI=0.87–1.36,P=0.39,I2=5%), while subjects with distal non-advanced or advanced adenoma had higher odds of PN/APN. Higher odds of PN/APN were observed for more severe distal lesions. Weaker association between distal and proximal findings was noticed in studies with higher quality, larger sample size, population-based design, and more stringent endoscopy quality-control measures. The Egger’s regression tests showed allP>0.05.
Conclusions:
Distal HP is not associated with PN/APN in asymptomatic screening population when compared with normal distal findings. Hence, the presence of distal HP alone detected by FS does not automatically indicate colonoscopy referral for all screening participants, as other risk factors of PN/APN should be considered
Bound States and Critical Behavior of the Yukawa Potential
We investigate the bound states of the Yukawa potential , using different algorithms: solving the Schr\"odinger
equation numerically and our Monte Carlo Hamiltonian approach. There is a
critical , above which no bound state exists. We study the
relation between and for various angular momentum quantum
number , and find in atomic units, , with , ,
, and .Comment: 15 pages, 12 figures, 5 tables. Version to appear in Sciences in
China
BOUT++: a framework for parallel plasma fluid simulations
A new modular code called BOUT++ is presented, which simulates 3D fluid
equations in curvilinear coordinates. Although aimed at simulating Edge
Localised Modes (ELMs) in tokamak X-point geometry, the code is able to
simulate a wide range of fluid models (magnetised and unmagnetised) involving
an arbitrary number of scalar and vector fields, in a wide range of geometries.
Time evolution is fully implicit, and 3rd-order WENO schemes are implemented.
Benchmarks are presented for linear and non-linear problems (the Orszag-Tang
vortex) showing good agreement. Performance of the code is tested by scaling
with problem size and processor number, showing efficient scaling to thousands
of processors.
Linear initial-value simulations of ELMs using reduced ideal MHD are
presented, and the results compared to the ELITE linear MHD eigenvalue code.
The resulting mode-structures and growth-rate are found to be in good agreement
(BOUT++ = 0.245, ELITE = 0.239). To our knowledge, this is the first time
dissipationless, initial-value simulations of ELMs have been successfully
demonstrated.Comment: Submitted to Computer Physics Communications. Revised to reduce page
count. 18 pages, 16 figure
Measurements of the observed cross sections for exclusive light hadron production in e^+e^- annihilation at \sqrt{s}= 3.773 and 3.650 GeV
By analyzing the data sets of 17.3 pb taken at GeV
and 6.5 pb taken at GeV with the BESII detector at the
BEPC collider, we have measured the observed cross sections for 12 exclusive
light hadron final states produced in annihilation at the two energy
points. We have also set the upper limits on the observed cross sections and
the branching fractions for decay to these final states at 90%
C.L.Comment: 8 pages, 5 figur
Search for the Rare Decays J/Psi --> Ds- e+ nu_e, J/Psi --> D- e+ nu_e, and J/Psi --> D0bar e+ e-
We report on a search for the decays J/Psi --> Ds- e+ nu_e + c.c., J/Psi -->
D- e+ nu_e + c.c., and J/Psi --> D0bar e+ e- + c.c. in a sample of 5.8 * 10^7
J/Psi events collected with the BESII detector at the BEPC. No excess of signal
above background is observed, and 90% confidence level upper limits on the
branching fractions are set: B(J/Psi --> Ds- e+ nu_e + c.c.)<4.8*10^-5, B(J/Psi
--> D- e+ nu_e + c.c.) D0bar e+ e- + c.c.)<1.1*10^-5Comment: 10 pages, 4 figure
Measurements of psi(2S) decays to octet baryon-antibaryon pairs
With a sample of 14 million psi(2S) events collected by the BESII detector at
the Beijing Electron Positron Collider (BEPC), the decay channels psi(2S)->p
p-bar, Lambda Lambda-bar, Sigma0 Sigma0-bar, Xi Xi-bar are measured, and their
branching ratios are determined to be (3.36+-0.09+-0.24)*10E-4,
(3.39+-0.20+-0.32)*10E-4, (2.35+-0.36+-0.32)*10E-4, (3.03+-0.40+-0.32)*10E-4,
respectively. In the decay psi(2S)->p p-bar, the angular distribution parameter
alpha is determined to be 0.82+-0.17+-0.04.Comment: 8 pages, 8 figure
Direct Measurements of the Branching Fractions for and and Determinations of the Form Factors and
The absolute branching fractions for the decays and
are determined using singly
tagged sample from the data collected around 3.773 GeV with the
BES-II detector at the BEPC. In the system recoiling against the singly tagged
meson, events for and events for decays are observed. Those yield
the absolute branching fractions to be and . The
vector form factors are determined to be
and . The ratio of the two form
factors is measured to be .Comment: 6 pages, 5 figure
- …