110,118 research outputs found
Equivalence of pion loops in equal-time and light-front dynamics
We demonstrate the equivalence of the light-front and equal-time formulations
of pionic corrections to nucleon properties. As a specific example, we consider
the self-energy of a nucleon dressed by pion loops, for both pseudovector and
pseudoscalar pion-nucleon couplings. We derive the leading and next-to-leading
nonanalytic behavior of the self-energy on the light-front, and show explicitly
their equivalence in the rest frame and infinite momentum frame in equal-time
quantization, as well as in a manifestly covariant formulation.Comment: 25 pages, 2 figures; typos corrected in Eqs. (A5), (A6), (A8
Multi-cell battery protection system
A multi-cell battery protection system is described wherein each cell has its own individual protective circuit. The protective circuits consist of a solid state comparator unit and a high current switching device such as a relay. The comparator units each continuously monitor the associated cell and when the cell voltage either exceeds a predetermined high level or falls below a predetermined low level, the relay is actuated whereby a bypass circuit is completed across the cell thereby effectively removing the cell from the series of cells
The Validity of Charge Symmetry for Parton Distributions
Recent measurements of the Gottfried sum rule have focused attention on the
possibility of substantial flavor symmetry breaking in the proton sea. This is
confirmed by pp and pD Drell-Yan processes measured at FNAL. Theoretical models
used to `prove' flavor symmetry breaking rely on the assumption of charge
symmetric parton distributions. Substantial charge symmetry violation [CSV]
could affect current tests of flavor symmetry. In this review we examine the
possibility of CSV for parton distributions. We first give definitions for
structure functions without making the usual assumption of charge symmetry.
Next we make estimates of CSV for both valence and sea quark distributions. We
list a set of relations which must hold if charge symmetry is valid, and review
current experimental limits on CSV. We propose a series of experimental tests
of charge symmetry. These tests could either detect CSV, or they could provide
stronger upper limits on CSV effects. We discuss CSV contributions to sum
rules, and we propose sum rules which could differentiate between flavor
symmetry, and charge symmetry violation in nuclear systems.Comment: 74 pages, including 26 figure
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