4,437 research outputs found
Isolating Excited States of the Nucleon in Lattice QCD
We discuss a robust projection method for the extraction of excited-state
masses of the nucleon from a matrix of correlation functions. To illustrate the
algorithm in practice, we present results for the positive parity excited
states of the nucleon in quenched QCD. Using eigenvectors obtained via the
variational method, we construct an eigenstate-projected correlation function
amenable to standard analysis techniques. The method displays its utility when
comparing results from the fit of the projected correlation function with those
obtained from the eigenvalues of the variational method. Standard nucleon
interpolators are considered, with and correlation
matrix analyses presented using various combinations of source-smeared,
sink-smeared and smeared-smeared correlation functions. Using these new robust
methods, we observe a systematic dependency of the nucleon excited-state masses
on source- and sink-smearing levels. To the best of our knowledge, this is the
first clear indication that a correlation matrix of standard nucleon
interpolators is insufficient to isolate the eigenstates of QCD.Comment: May 2009.13pp, Minor changes and references adde
Low-lying positive-parity excited states of the nucleon
We present an overview of the correlation-matrix methods developed recently
by the CSSM Lattice Collaboration for the isolation of excited states of the
nucleon. Of particular interest is the first positive-parity excited-state of
the nucleon known as the Roper resonance. Using eigenvectors of the correlation
matrix we construct parity and eigenstate projected correlation functions which
are analysed using standardized methods. The robust nature of this approach for
extracting the eigenstate energies is presented. We report the importance of
using a variety of source and sink smearings in achieving this. Ultimately the
independence of the eigenstate energies from the interpolator basis is
demonstrated. In particular we consider correlation matrices built
from a variety of interpolators and smearing levels. Using FLIC fermions to
access the light quark mass regime, we explore the curvature encountered in the
energy of the states as the chiral limit is approached. We report a low-lying
Roper state contrasting earlier results using correlation matrices. To the best
of our knowledge, this is the first time a low-lying Roper resonance has been
found using correlation matrix methods. Finally, we present our results in the
context of the Roper results reported by other groups.Comment: 8 pages, 4 figures., Presented at the XXVII International Symposium
on Lattice Field Theory, July 26-31, 2009, Peking University, Beijing, Chin
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SIERRA framework version 4 : solver services.
Several SIERRA applications make use of third-party libraries to solve systems of linear and nonlinear equations, and to solve eigenproblems. The classes and interfaces in the SIERRA framework that provide linear system assembly services and access to solver libraries are collectively referred to as solver services. This paper provides an overview of SIERRA's solver services including the design goals that drove the development, and relationships and interactions among the various classes. The process of assembling and manipulating linear systems will be described, as well as access to solution methods and other operations
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A New Green Salamander in the Southern Appalachians: Evolutionary History of Aneides aeneus and Implications for Management and Conservation with the Description of a Cryptic Micro-endemic Species (vol 107, pg 748, 2019)
Creatine supplementation enhances muscle force recovery after eccentrically-induced muscle damage in healthy individuals
Eccentric exercise-induced damage leads to reductions in muscle force, increased soreness, and impaired muscle function. Creatine monohydrate's (Cr) ergogenic potential is well
established; however few studies have directly examined the effects of Cr supplementation on recovery after damage. We examined the effects of Cr supplementation on muscle proteins and force recovery after eccentrically-induced muscle damage in healthy individuals. The major finding of this investigation was a significant improvement in the rate of recovery of knee extensor muscle function after Cr supplementation following injury
Ordering of Spin- Excitations of the Nucleon in Lattice QCD
We present results for the negative parity low-lying state of the nucleon,
(1535 MeV) , from a variational analysis
method. The analysis is performed in quenched QCD with the FLIC fermion action.
The principal focus of this paper is to explore the level ordering between the
Roper () and the negative parity ground () states
of the nucleon. Evidence of the physical level ordering is observed at light
quark masses. A wide variety of smeared-smeared correlation functions are used
to construct correlation matrices. A comprehensive correlation matrix analysis
is performed to ensure an accurate isolation of the state.Comment: 9 page
Efficacy of a New Angioplasty Catheter for Severely Narrowed Coronary Lesions
Conventional over the wire dilation catheters may be unsuccessful in crossing coronary lesions that are severely narrowed. Hence, a new, extremely low profile coronary angioplasty catheter specifically designed to dilate such lesions was investigated. The catheter features a 2.0, 2.5 or 3.0 mm (inflated diameter) balloon mounted on a guide wire. The deflated profile of the 2.0 mm balloon measures 0.020 ± 0.001 in. (0.51 ± 0.03 mm). The catheter can be used in conjunction with 7F angiographic or 8F guide catheters.The catheter was used in 61 patients, aged 43 to 86 years, with predominantly Canadian Cardiovascular Society class III-IV angina. Dilation was attempted in 77 lesions. Lesion length averaged 5.7 ± 3.1 mm (mean ± 1 SD), minimal diameter 0.51 ± 0.25 mm and internal vessel diameter 2.27 ± 0.43 mm. Sixty lesions (78%) were successfully dilated to <50% residual stenosis with this catheter alone; nine lesions were further dilated with a larger balloon catheter. The new catheter was unable to cross 13 lesions (17%); only 2 of these lesions were subsequently crossed with a conventional over the wire system. On the other hand, the catheter was used after failure of conventional dilating catheters in 21 lesions and was successful in 16. The new catheter was particularly valuable for distal lesions and those demonstrating 90 to 99 % diameter reduction. For all lesions crossed, stenosis decreased from 76 ± 11 to 29 ± 12% after 2.9 ± 2.7 inflations and peak inflation pressure of 8.0 ± 2.9 bar. Complications were rare; coronary occlusion occurred in two lesions (3%) and dissection in three lesions (4%). There were no instances of death or emergency coronary artery bypass surgery.Thus, this new angioplasty catheter was uniquely effective and safe in patients with severe coronary lesions. Importantly, success was often achieved after failure of conventional angioplasty catheters
Transplanting Kidneys Without Points for HLA‐B Matching: Consequences of the Policy Change
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87103/1/j.1600-6143.2011.03606.x.pd
Survival-Time Distribution for Inelastic Collapse
In a recent publication [PRL {\bf 81}, 1142 (1998)] it was argued that a
randomly forced particle which collides inelastically with a boundary can
undergo inelastic collapse and come to rest in a finite time. Here we discuss
the survival probability for the inelastic collapse transition. It is found
that the collapse-time distribution behaves asymptotically as a power-law in
time, and that the exponent governing this decay is non-universal. An
approximate calculation of the collapse-time exponent confirms this behaviour
and shows how inelastic collapse can be viewed as a generalised persistence
phenomenon.Comment: 4 pages, RevTe
The giant lobes of Centaurus A observed at 118 MHz with the Murchison Widefield Array
We present new wide-field observations of Centaurus A (Cen A) and the surrounding region at 118MHz with the Murchison Widefield Array (MWA) 32-tile prototype, with which we investigate the spectral-index distribution of Cen A's giant radio lobes.We compa
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