Robert D. Carlitz

The role of the axial anomaly in measuring spin-dependent parton distributions

It is shown that the forward matrix elements of j{sub 5}{sup {mu}}, the flavor singlet axial vector current, do not measure the helicity carried by quarks and anti-quarks but also include a spin-dependent gluonic component due to the anomaly. Detailed phenomenological and field theoretic reasons are given for the necessity of a gluonic component in the matrix element of j{sub 5}{sup {mu}}. The first higher order corrections to the basic box and triangle graphs are discussed and shown not to modify the conclusions drawn in the leading order calculation. We close with a few comments on the possible phenomenological implications of the anomalous contribution. 25 refs., 6 figs.

Light Quarks and Instantons

Abstract Instantons and anti-instantons can profoundly influence the structure of a non-Abelian gauge theory involving N flavors of massless quarks. Interactions of the quarks with these pseudoparticles can spontaneously generate a quark mass, break the theorys SU(N) × SU(N) chiral symmetry and bind quark-antiquark pairs to form N2 − 1 Goldstone bosons. If the spontaneously generated quark mass is small, multipseudoparticle configurations can be treated in a dilute gas approximation.

Classical Paths and Quantum Mechanics

Abstract In the semiclassical limit, the path integral description of quantum mechanics is dominated by classical paths. A classical path method is developed to extract energy levels and wavefunctions for a one-dimensional quantum system and it is shown that this method reproduces the results of the WKB approach. The classical path method generalizes the instanton method and provides new insights into instanton interactions. It provides a convenient and intuitive approach to many problems in quantum mechanics and field theory.

Instanton induced interactions

Abstract Quarks interact under the influence of instantons. These interactions affect the wavefunctions of pions and nucleons and produce differences in the transverse momentum distributions of the up and down quarks within a nucleon.

Extending common knowledge

Common knowledge: Pittsburgh is a school networking project which is developing network connectivity and curricular applications in the Pittsburgh Public Schools. With its emphasis on the curriculum and its efforts to institutionalize the use of networking technology, the project offers a useful model for other school districts to follow. The present paper describes how the project has expanded from its initial structure, delineates specific products that have been produced and indicates directions in which future expansion is likely to take place.

The structure of the multi-instanton gas☆

Abstract We parametrize the q -instanton solutions of an SU(2) gauge theory in terms of the positions of 2 q constituent particles or “instanton quarks”. Explicit computations of lowest order quantum fluctuations about the q = 1 and q = 2 solutions show that the short-distance interaction between instanton quark pairs is logarithmic. Extending these interactions to arbitrary q , we describe the multi-instanton gas as a plasma of instanton quarks.

A physical model of the instanton gas

Abstract We introduce a physical parametrization for the instanton solutions of non-abelian gauge theories and discuss the thermodynamics of a multi-instanton gas.

The short-distance structure of instantons

Abstract The short-distance structure of a quark propagator in an instanton background field is analyzed. This analysis describes the influence of instantons upon physical processes such as electron-positron annihilation and the deep inelastic scattering of leptons from hadrons.

Creating common knowledge: school networking in an urban setting

Describes a project currently under way in the Pittsburgh Public Schools seeking to develop new environments for teaching and learning using the technology of wide area computer networks. The history of this project offers lessons for other school districts which might wish to develop similar resources for their own use. Extracts a set of guidelines that can be followed by these other school districts.

Single spin asymmetries in muon pair production

Theoretical analyses of polarized leptoproduction data suggest that the polarized gluon structure function might be large, but there has been no independent measurement of this quantity. Measurements of single spin asymmetries in the production of muon pairs from the scattering of two protons, one of which is longitudinally polarized, can be interpreted in terms of polarized gluon and polarized quark structure functions. Here we compute the asymmetries for the parton subprocesses that contribute to the measured muon pair production.