Dyson-Schwinger Equations - aspects of the pion

The contemporary use of Dyson-Schwinger equations in hadronic physics is exemplified via applications to the calculation of pseudoscalar meson masses, and inclusive deep inelastic scattering with a determination of the pion's valence-quark distribution function.Comment: 4 pages. Contribution to the Proceedings of ``DPF 2000,'' the Meeting of the Division of Particles and Fields of the American Physical Society, August 9-12, 2000, Department of Physics, the Ohio State University, Columbus, Ohi

Vector meson form factors and their quark-mass dependence

The electromagnetic form factors of vector mesons are calculated in an explicitly Poincar\'e covariant formulation, based on the Dyson--Schwinger equations of QCD, that respects electromagnetic current conservation, and unambiguously incorporates effects from vector meson poles in the quark-photon vertex. This method incorporates a 2-parameter effective interaction, where the parameters are constrained by the experimental values of chiral condensate and $f_{\pi}$. This approach has successfully described a large amount of light-quark meson experimental data, e.g. ground state pseudoscalar masses and their electromagnetic form factors; ground state vector meson masses and strong and electroweak decays. Here we apply it to predict the electromagnetic properties of vector mesons. The results for the static properties of the $\rho$-meson are: charge radius $= 0.54 {\rm fm}^2$, magnetic moment $\mu = 2.01$, and quadrupole moment ${\cal Q} = -0.41$. We investigate the quark mass dependence of these static properties and find that our results at the charm quark mass are in agreement with recent lattice simulations. The charge radius decreases with increasing quark mass, but the magnetic moment is almost independent of the quark mass.Comment: 13 pages, 7 figure

Draft Model for Network Information System: Working Paper Series--03-15

This paper presents a model to aid researchers with the task of identifying the elements of a network-based information system in their studies. If the elements are not properly identified, the results of a study may be misinterpreted or lost. The elements of network-based information can be divided into three major categories: Use: people using or benefiting from use of the information system, procedures used by the people, and functional area data; Applications: people developing or maintaining software, development and maintenance procedures, application configuration data, and the applications; Infrastructure: systems personnel, systems procedures, protocols, system data, system software, and hardware. Proper identification of network-based information system elements can make delimiting the study easier and make the results more convincing

Chiral Extrapolation of Lattice Data for Heavy Meson Hyperfine Splittings

We investigate the chiral extrapolation of the lattice data for the light-heavy meson hyperfine splittings D^*-D and B^*-B to the physical region for the light quark mass. The chiral loop corrections providing non-analytic behavior in m_\pi are consistent with chiral perturbation theory for heavy mesons. Since chiral loop corrections tend to decrease the already too low splittings obtained from linear extrapolation, we investigate two models to guide the form of the analytic background behavior: the constituent quark potential model, and the covariant model of QCD based on the ladder-rainbow truncation of the Dyson-Schwinger equations. The extrapolated hyperfine splittings remain clearly below the experimental values even allowing for the model dependence in the description of the analytic background.Comment: 14 pages, 4 figures, typos corrected, presentation clarifie

The effect of qualitative expressions of magnitude in the letter to shareholders on investors' perceptions of earnings performance: Working paper series--03-18

Annual reports issued by publicly traded firms are important documents for communicating the financial performance of a company. In addition to the financial statements, annual reports contain non-numerical information (i.e., written expressions). The letter to shareholders is typically the first non-numerical item representing management's communication that a reader comes to in an annual report. The primary content of the letter to shareholders is a series of written expressions used to describe the company's financial situation. We report how readers' perceptions are influenced by one type of written expression often found in the letter to shareholders: Qualitative expressions of magnitude (e.g., "minimal," "moderate" or "sizable") used to describe the results of operations. Top management (e.g., presidents) very often uses qualitative expressions of magnitude in the letter to shareholders to describe the quantitative financial performance of the company found in the accompanying financial statements. Holding the actual percentage change in corporate earnings and other contextual factors constant, we find that the type of expression used in the letter to shareholders does influence readers' perception of financial performance reported in the financial statements. In addition, we find evidence that less sophisticated investors are influenced more by the use of qualitative expressions of magnitude

Valence-quark distributions in the pion

We calculate the pion's valence-quark momentum-fraction probability distribution using a Dyson-Schwinger equation model. Valence-quarks with an active mass of 0.30 GeV carry 71% of the pion's momentum at a resolving scale q_0=0.54 GeV = 1/(0.37 fm). The shape of the calculated distribution is characteristic of a strongly bound system and, evolved from q_0 to q=2 GeV, it yields first, second and third moments in agreement with lattice and phenomenological estimates, and valence-quarks carrying 49% of the pion's momentum. However, pointwise there is a discrepancy between our calculated distribution and that hitherto inferred from parametrisations of extant pion-nucleon Drell-Yan data.Comment: 8 pages, 3 figures, REVTEX, aps.sty, epsfig.sty, minor corrections, version to appear in PR

Symmetry breaking via fermion 4-point functions

We construct the effective action and gap equations for nonperturbative fermion 4-point functions. Our results apply to situations in which fermion masses can be ignored, which is the case for theories of strong flavor interactions involving standard quarks and leptons above the electroweak scale. The structure of the gap equations is different from what a naive generalization of the 2-point case would suggest, and we find for example that gauge exchanges are insufficient to generate nonperturbative 4-point functions when the number of colors is large.Comment: 36 pages, uses Revtex and eps files for figure

Signal words and signal icons in application control and information technology exception messages - Hazard matching and habituation effects: Working paper series--06-05

People often encounter warnings in various life situations. These warnings typically include a variety and combination of signal phrases (e.g., "Deadly") and signal icons (e.g., a skull and cross-bones). Users of information technology (IT) frequently encounter such signal words and icons in "exception messages" that appear on computer screens when the user performs an incorrect action or if a condition could arise that may result in a negative occurrence. For example, in the context of accounting application controls which deal with exposures within specific computer application programs. This paper reports the results of two experiments. The first examines the "arousal strength" associated with various signal words and signal icons that are commonly used in IT exception messages. An elicitation exercise was completed by 316 participants, in which each participant viewed exception messages containing combinations of signal words and signal icons and provided their perception as to the severity of a computer problem communicated by the exception message. The results can be used to achieve "hazard matching," whereby the severity of hazard that is implied by the signal word and icon within the exception message can be matched to the level of the potential hazard faced by the user. The second experiment investigated the factor of habituation and if the negative results of habituation can be overcome through the design of exception messages. A strong habituation effect was found to exist and the effect was also found to be mitigated by altering the signal word and icon combination of an exception message

Distance dependence of force and dissipation in non-contact atomic force microscopy on Cu(100) and Al(111)

The dynamic characteristics of a tip oscillating in the nc-AFM mode in close vicinity to a Cu(100)-surface are investigated by means of phase variation experiments in the constant amplitude mode. The change of the quality factor upon approaching the surface deduced from both frequency shift and excitation versus phase curves yield to consistent values. The optimum phase is found to be independent of distance. The dependence of the quality factor on distance is related to 'true' damping, because artefacts related to phase misadjustment can be excluded. The experimental results, as well as on-resonance measurements at different bias voltages on an Al(111) surface, are compared to Joule dissipation and to a model of dissipation in which long-range forces lead to viscoelastic deformations