Weak and Electromagnetic Radiative Corrections in Atomic Physics

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Radiative corrections have played a central role in the development of theoreticalphysics since the original successes of Quantum Electrodynamics (QED) in the late1940's. Their calculation in atoms and ions is technically challenging because of thecomplexity of the electron propagator in bound states. Two theoretical tools willbe used in this project to attack this problem. The first, S-matrix theory, is mostapplicable to highly charged ions. QED effects are highly enhanced in these ions,and recent advances in experiment provide a wealth of data sensitive to this physics.S-matrix theory can be used to systematically calculate radiative corrections in theseions, provide tests of QED, and possibly uncover new physics through the comparisonof theory and experiment. The existence of an expansion parameter, 1/Z, leads tothe simplification of having to deal with a limited set of Feynman diagrams. A majorpart of this work involves the calculation of these diagrams, which should allowthe above-mentioned tests.In neutral atoms the 1/Z expansion parameter is not available, and precision testsare much more difficult. A major development of recent years has been the applicationof non-relativistic QED (NRQED) to few-electron systems. This technique allows oneto start with the Schroedinger equation, which can be solved with high accuracy forfew-electron atoms. NRQED provides a systematic method to account for relativisticand QED corrections. Another major component of the proposed research is applica-tion of this method to the fine structure of helium, where comparison of sufficientlyadvanced theory with already existent experiments should allow a determination ofthe fine structure constant with high accuracy.Finally, the evaluation of radiative corrections to parity nonconserving (PNC)processes in heavy neutral atoms is proposed. The earliest particle physics evaluationsof this radiative correction, which involved free propagators, are significantly changedwhen bound propagators are used. A full calculation has not yet been carried out,but work carried out under the previous grant should be generalizable to this complextask, which has important particle physics implications.