Sapirstein, J.R.

Stanford Univ., CA (USA)

Stanford Univ., CA (USA)

AbstractAbstract

[en] Typical infrared effects in several gauge field theories with massless particles are investigated in perturbation theory. It is first shown that divergences occurring in individual Feynman graphs arising from integrations over the long-wavelength modes of the fields cancel when the graphs are grouped together in a particular way, in a generalization of the Bloch-Nordsieck treatment of QED. As one of the requirements of finiteness is renormalization of the vector propagator off shell, the charge in these theories is not directly related to classical experiment. In an effort to find the meaning of charge the low-energy theorem is considered. Although in lowest order the graphs reproduce the Thompson limit, it is found that loop corrections are singular in the low-energy limit; a simple definition of the charge is thus precluded. Finally, the behavior of the quark color magnetic moment is treated. An apparent infrared singularity of this moment is shown to be due to an improper use of perturbation theory, and is removed and replaced with a finite, field-dependent moment, by use of Furry picture propagators

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1979; 91 p; University Microfilms Order No. 80-06,347; Thesis (Ph. D.).

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Report

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Thesis/Dissertation

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[en] The theory of highly charged many-electron ions is discussed as a branch of Quantum Electrodynamics (QED). Many-body perturbation theory, which converges rapidly for highly charged ions, is shown to be a subset of QED perturbation theory, which also leads to radiative corrections. Recent progress in the evaluation of the one-loop Lamb shift in non-Coulomb potentials is described, and the prospects for evaluation of higher order radiative corrections discussed. Comparison with experiment for highly charged heliumlike, lithiumlike, and neonlike ions is made

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1993 American Physical Society annual meeting on atomic, molecular, and topical physics; Reno, NV (United States); 16-19 May 1993; CONF-9305421--

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Journal Article

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Conference

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[en] A review of the present status of Quantum Electrodynamics for lepton anomalies and bound states is presented. Emphasis is given to future limitations in progress due to strong interaction uncertainties and the possible extension of precision tests to many electron systems

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Atomic theory workshop on relativistic and QED effects in heavy atoms; Gaithersburg, MD (USA); 23-24 May 1985; CONF-8505189--

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Journal Article

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Conference

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[en] Recent advances in the theoretical calculation of ground state muonium hyperfine splitting are described. The role of the known nonrelativistic Coulomb Green's function as the basis of approximation schemes is emphasized

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Barat, A.O; p. 83-95; 1984; p. 83-95; Plenum Press; New York, NY (USA); NATO advanced study institute on quantum electrodynamics and quantum optics; Boulder, CO (USA); 27 May - 8 Jun 1983

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Book

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Conference

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[en] A perturbative expansion of the electron's Dirac Coulomb propagator around a nonrelativistic form is used to evaluate the one-loop p nonrecoil corrections to ground-state hyperfine splitting in p hydrogenic atoms. A contribution previously estimated as (α/π)(Zα)

^{2}x (18.36 +- 5)E/sub F/ is found to be (α/π) (Zα)^{2}(15.10 +- 0.29)E/sub F/. Theory and experiment are compared for muonium hyperfine splitting and consequences for the fine-structure constant are discussedPrimary Subject

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Journal Article

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Physical Review Letters; ISSN 0031-9007; ; v. 51(11); p. 985-987

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[en] The lowest-order quantum electrodynamic corrections to the energy levels of quarks bound in a spherical cavity are evaluated over a wide range of values of the quark mass. It is found that the self-energy is positive for massless quarks and decreases smoothly as the quark mass increases. The interaction energy between quarks is also calculated and found to dominate the self-energy correction. For this model, the vacuum polarization correction vanishes

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Journal Article

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Physical Review Letters; ISSN 0031-9007; ; v. 54(6); p. 514-517

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CORRECTIONS, DIAGRAMS, DIFFERENTIAL EQUATIONS, ELECTRODYNAMICS, ELEMENTARY PARTICLES, ENERGY, EQUATIONS, EXTENDED PARTICLE MODEL, FIELD EQUATIONS, FIELD THEORIES, INFORMATION, INTERACTIONS, MATHEMATICAL MODELS, PARTIAL DIFFERENTIAL EQUATIONS, PARTICLE MODELS, POSTULATED PARTICLES, QUANTUM FIELD THEORY, WAVE EQUATIONS

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[en] We present a detailed description of the calculation of radiative-recoil corrections to the ground-state hyperfine splitting in muonium and positronium to order α

^{2}E/sub F/, the results of which were previously reported. All these corrections involve two-photon exchanges with one-loop radiative corrections to either a photon or a lepton. The QED vacuum polarization corrections are evaluated completely analytically to the order of interest. The hadronic contributions are estimated and found to be very small. As a preliminary to the lepton line calculation, a compact expression is derived for the radiative correction to such lines. This factor is then applied in a number of different contexts: the recalculation of the old nonrecoil result, which is known analytically; the analytic evaluation of terms of order α^{2}(m/sub e//m/sub μ/)ln(m/sub μ//m/sub e/ )E/sub F/, which arise from the electron leg; and the nonlogarithmic terms from both lines, which require numerical calculations. The muonium results are ν+e^{-}= (α/π)^{2}(m/sub e//m /sub μ/) [-2ln^{2}(m/sub μ//m/sub e/)+(13/1 2)ln(m/sub μ//m/sub e/)+18.18 +- 0. 58]E/sub F/ and those for positronium are ν/sub e/^{+}e^{-}= α^{2}(-1.788 +- 0 .004)E/sub F/, where E/sub F/ for positronium does not include the annihilation contributionPrimary Subject

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Journal Article

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Physical Review. D, Particles Fields; ISSN 0556-2821; ; v. 29(10); p. 2290-2314

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[en] A compact expression for one-loop radiative corrections to lepton lines in positronium and muonium hyperfine splitting is presented. It is valid for hyperfine-splitting contributions of order α

^{2}E/sub F/, including the effects of recoil to all orders. For muonium, known nonrecoil parts of this contribution are easily evaluated analytically, as is a previously calculated radiative-recoil contribution of order α^{2}E/sub F/(m/sub e//m/sub μ/)ln(m/sub μ//m/sub e/). Nonlogarithmic radiative-recoil corrections obtained by numerical evaluation of this expression yield new contributions of 2.64 +- 0.07 kHz for muonium and -11.12 +- 0.02 MHz for positroniumPrimary Subject

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Journal Article

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Physical Review Letters; ISSN 0031-9007; ; v. 51(11); p. 982-984

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