692 research outputs found
IR finiteness of the ghost dressing function from numerical resolution of the ghost SD equation
We solve numerically the Schwinger-Dyson (SD hereafter) ghost equation in the
Landau gauge for a given gluon propagator finite at k=0 (alpha_gluon=1) and
with the usual assumption of constancy of the ghost-gluon vertex ; we show that
there exist two possible types of ghost dressing function solutions, as we have
previously inferred from analytical considerations : one singular at zero
momentum, satisfying the familiar relation alpha_gluon+2 alpha_ghost=0 between
the infrared exponents of the gluon and ghost dressing functions(in short,
respectively alpha_G and alpha_F) and having therefore alpha_ghost=-1/2, and
another which is finite at the origin (alpha_ghost=0), which violates the
relation. It is most important that the type of solution which is realized
depends on the value of the coupling constant. There are regular ones for any
coupling below some value, while there is only one singular solution, obtained
only at a critical value of the coupling. For all momenta k<1.5 GeV where they
can be trusted, our lattice data exclude neatly the singular one, and agree
very well with the regular solution we obtain at a coupling constant compatible
with the bare lattice value.Comment: 17 pages, 3 figures (one new figure and a short paragraph added
Power Corrections to Perturbative QCD and OPE in Gluon Green Functions
We show that QCD Green functions in Landau Gauge exhibit sizable
corrections to the expected perturbative behavior at energies as high as 10
GeV. We argue that these are due to a -condensate which does not vanish
in Landau gauge.Comment: 3 pages 1 figure lattice2001 (gaugetheories
On the leading OPE corrections to the ghost-gluon vertex and the Taylor theorem
This brief note is devoted to a study of genuine non-perturbative corrections
to the Landau gauge ghost-gluon vertex in terms of the non-vanishing
dimension-two gluon condensate. We pay special attention to the kinematical
limit which the bare vertex takes for its tree-level expression at any
perturbative order, according to the well-known Taylor theorem. Based on our
OPE analysis, we also present a simple model for the vertex, in acceptable
agreement with lattice data.Comment: Final version published in JHE
Quark propagator and vertex: systematic corrections of hypercubic artifacts from lattice simulations
This is the first part of a study of the quark propagator and the vertex
function of the vector current on the lattice in the Landau gauge and using
both Wilson-clover and overlap actions. In order to be able to identify lattice
artifacts and to reach large momenta we use a range of lattice spacings. The
lattice artifacts turn out to be exceedingly large in this study. We present a
new and very efficient method to eliminate the hypercubic (anisotropy)
artifacts based on a systematic expansion on hypercubic invariants which are
not SO(4) invariant. A simpler version of this method has been used in previous
works. This method is shown to be significantly more efficient than the popular
``democratic'' methods. It can of course be applied to the lattice simulations
of many other physical quantities. The analysis indicates a hierarchy in the
size of hypercubic artifacts: overlap larger than clover and propagator larger
than vertex function. This pleads for the combined study of propagators and
vertex functions via Ward identities.Comment: 14 pags., 9 fig
A Correlational Study Examining the Relationship Between Restorative Practices and School Climate in Selected Elementary Schools in a Large Mid-Atlantic Urban School District
Punitive consequences are extensively utilized when dealing with school discipline. Recently, positive approaches to discipline, such as restorative practices, have been implemented in many schools to address school discipline concerns and to improve school climate. Restorative practices is a philosophy that focuses on building positive relationships by changing mindsets. This study took place in a large mid-atlantic urban school district. The goal of the study was to determine the relationship between restorative practices and school climate from the perspectives of school staff members who utilize restorative practices in their schools. A quantitative correlational research design was utilized for this study to examine the relationship between restorative practices and school climate. Findings from this study indicated a strong positive correlation between measures of restorative practice and school climate
Testing Landau gauge OPE on the Lattice with a Condensate
Using the operator product expansion we show that the correction
to the perturbative expressions for the gluon propagator and the strong
coupling constant resulting from lattice simulations in the Landau gauge are
due to a non-vanishing vacuum expectation value of the operator .
This is done using the recently published Wilson coefficients of the identity
operator computed to third order, and the subdominant Wilson coefficient
computed in this paper to the leading logarithm. As a test of the applicability
of OPE we compare the estimated from the gluon propagator and
the one from the coupling constant in the flavourless case. Both agree within
the statistical uncertainty: GeV.
Simultaneously we fit \Lams = 233(28) MeV in perfect agreement with previous
lattice estimates. When the leading coefficients are only expanded to two
loops, the two estimates of the condensate differ drastically. As a consequence
we insist that OPE can be applied in predicting physical quantities only if the
Wilson coefficients are computed to a high enough perturbative order.Comment: 15 pages, LaTex file with 5 figure
Enterprise Social Networks : Effective Internal Organizational Communication Strategies
Social Networking Sites (SNSs) such as Facebook and Twitter have reinvented how publics communicate with one another. Enterprise Social Networks (ESNs) are a form of Social Network Sites (SNS) which many organizations are adopting within their communication practices. The primary goal of ESNs is to engage employees through social interaction which is intended to create company communities which users can use to access business information, team updates and team performance statistics. The current study examines assumptions present in purveyor literature about how ESNs are intended to provide benefit in six aspects of organizational development: organizational communication, information communication technology, technology mediated communication, employee motivation, knowledge sharing and building relationship. Several ESNs were evaluated according to these six categories. Building Relationships and Organizational Communication were found in five of the ESNs analyzed; Technology Mediated Communication and Knowledge Sharing were found in four of the ESNs analyzed; Information Communication Technology was found in two of the ESNs; and Employee Motivation was not found in either of the ESNs analyzed. Overall, the study finds that purveyors intend ESNs to contribute to a variety, but not all, of the identified aspects
O.P.E. and Power Corrections to the QCD coupling constant
Lattice data seems to show that power corrections should be convoked to
describe appropriately the transition of the QCD coupling constant running from
U.V. to I.R. domains. Those power corrections for the Landau-gauge MOM coupling
constant in a pure Yang-Mills theory (N_f=0) are analysed in terms of Operator
Product Expansion (O.P.E.) of two- and three-point Green functions, the gluon
condensate emerging from this study. The semi-classical picture given by
instantons can be also used to look for into the nature of the power
corrections and gluon condensate.Comment: 5 pages, talk given at XXX International Meeting on Fundamental
Physics, Jaca 200
Describing gluons at zero and finite temperature
Any description of gluons requires a well-defined gauge. This is complicated
non-perturbatively by Gribov copies. A possible method-independent gauge
definition to resolve this problem is presented and afterwards used to study
the properties of gluons at any temperature. It is found that only
chromo-electric properties reflect the phase transition. From these the
gauge-invariant phase transition temperature is determined for SU(2) and SU(3)
Yang-Mills theory independently.Comment: 3 pages, 1 figure. Talk given at "The 5-th International Conference
on Quarks and Nuclear Physics", Beijing, China, and at "Quarks, Hadrons, and
the Phase Diagram of QCD", St. Goar, Germany, both September 2009. Submitted
to the QNP proceeding
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