arXiv subjects

John P. Costella

Publications and source records attributed to John P. Costella.

9 recordsLinked to original sources

arXiv2004

A new lattice gauge action without scaling artifacts

I describe a new way of constructing a gauge action that eliminates scaling artifacts, by writing the continuum formalism in terms of "gauge links" (Schwinger line integrals) and using the optimal SLAC representation of the lattice derivative. Computational performance can be maintained by implementing the action as a "stochastic" operator, as has been recently implemented in the MILC code for the optimal D-slash operator and the antialiasing filter.

hep-lat↗

arXiv2004

The aliasing problem in lattice field theory

The intrinsically nonlinear nature of quantum field theory provides a fundamental complication for lattice calculations, when the physical implications of the subtleties of Fourier theory are taken into account. Even though the fundamental fields are constrained to the first Brillouin zone, Fourier theory tells us that the high-momentum components of products of these fields "bleed into" neighbouring Brillouin zones, where they "alias" (or "masquerade") as low-momentum contributions, violating the conservation of energy and momentum, and fundamentally distorting calculations. In this paper I offer a general strategy for eliminating the artefacts of aliasing in practical calculations.

hep-lat↗

arXiv2002

A new proposal for the fermion doubling problem. II. Improving the operators for finite lattices

In a previous paper I showed how the ideal SLAC derivative and second-derivative operators for an infinite lattice can be obtained in simple closed form in position space, and implemented very efficiently in a stochastic fashion for practical calculations on finite lattices. In this second paper I show how the small (order 1/N) errors introduced by truncating the operators to a finite lattice may be removed by a small adjustment of coefficients, without incurring any additional computational cost. The derivation of these results is again presented in a simple, pedagogical fashion.

hep-lat↗

arXiv2002

A new proposal for the fermion doubling problem

In this paper I propose the use of a lattice derivative operator that is equivalent to the ideal SLAC derivative operator in all lattice calculations, but without the prohibitively expensive computational cost of the latter. A pedagogical motivation and derivation of the closed form of the SLAC derivative in position space is presented, and the proposed method for its cost-effective implementation is presented in detail.

hep-lat↗

arXiv2001

The Thomas rotation

We review why the Thomas rotation is a crucial facet of special relativity, that is just as fundamental, and just as "unintuitive" and "paradoxical", as such traditional effects as length contraction, time dilation, and the ambiguity of simultaneity. We show how this phenomenon can be quite naturally introduced and investigated in the context of a typical introductory course on special relativity, in a way that is appropriate for, and completely accessible to, undergraduate students. We also demonstrate, in a more advanced section aimed at the graduate student studying the Dirac equation and relativistic quantum field theory, that careful consideration of the Thomas rotation will become vital as modern experiments in particle physics continue to move from unpolarized to polarized cross-sections.

hep-ph↗

arXiv1997

Classical antiparticles

We review how antiparticles may be introduced in classical relativistic mechanics, and emphasize that many of their paradoxical properties can be more transparently understood in the classical than in the quantum domain.

hep-ph↗

arXiv1995

[p,q] does not equal (i h-bar)

In this short note, I point out that [p,q] does not equal (i h-bar), contrary to the original claims of Born and Jordan, and Dirac. Rather, [p,q] is equal to something that is *infinitesimally different* from (i h-bar). While this difference is usually harmless, it does provide the solution of the Born-Jordan "trace paradox" of [p,q]. More recently, subtleties of a very similar form have been found to be of fundamental importance in quantum field theory.

quant-ph↗

arXiv1995

The Foldy-Wouthuysen transformation

The Foldy-Wouthuysen transformation of the Dirac Hamiltonian is generally taught as simply a mathematical trick that allows one to obtain a two-component theory in the low-energy limit. It is not often emphasized that the transformed representation is the only one in which one can take a meaningful *classical limit*, in terms of particles and antiparticles. We briefly review the history and physics of this transformation.

hep-ph↗

arXiv1993

Electromagnetic Deflection of Spinning Particles

We show that it is possible to obtain self-consistent and physically acceptable relativistic classical equations of motion for a point-like spin-half particle possessing an electric charge and a magnetic dipole moment, directly from a manifestly covariant Lagrangian, if the classical degrees of freedom are appropriately chosen. It is shown that the equations obtained encompass the well-tested Lorentz force and Thomas--Bargmann--Michel--Telegdi spin equations, as well as providing a definite specification of the classical _magnetic_dipole_ force_, whose exact form has been the subject of recent debate. Radiation reaction---the force and torque on an accelerated particle due to its self-interaction---is neglected at this stage.

hep-ph↗