| 1. |
|
|
| 2. |
|
|
| 3. |
- Holmberg, J., et al.
(författare)
-
Coulomb-gauge calculation of the combined effect of correlation and QED for heliumlike highly charged ions
- 2015
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947. ; 92:1
-
Tidskriftsartikel (refereegranskat)abstract
- We present numerical results for the energy shift due to the combination of Coulomb-correlation and quantum-electrodynamic effects in the ground state of heliumlike highly charged ions. The combined effect of two or more Coulomb interactions together with a single retarded photon, including radiative effects, is calculated for various atomic numbers in the range Z = 14 to Z = 50. One step in our computational scheme involves the evaluation of the Coulomb-screened self-energy at the two-photon level, and we present a detailed comparison between the Coulomb and Feynman gauges with regard to the various contributions to this effect.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Lindgren, Ingvar, 1931, et al.
(författare)
-
Combination of many-body perturbation theory and quantum electrodynamics
- 2015
-
Ingår i: Theoretical Chemistry accounts. - : Springer Science and Business Media LLC. - 1432-881X .- 1432-2234. ; 134:11
-
Tidskriftsartikel (refereegranskat)abstract
- A procedure for energy-dependent perturbation expansion has been developed, based upon the covariant evolution operator method. This makes it possible to treat energy-dependent perturbations very much like the energy-independent ones in standard many-body perturbation theory. This has been applied to the non-radiative QED perturbations (retardation and virtual electron-positron pairs) as well as the radiative ones (electron self-energy, vacuum polarization and vertex correction). The combination of QED and electron correlation, beyond two-photon exchange, has been evaluated, using the Coulomb gauge. It turned out that in that gauge the extremely time-consuming model-space contributions of the self-energy and vertex corrections do not have to be evaluated in full. In the Feynman gauge no sensible results could be obtained in this way, as is demonstrated by the numerical results.
|
|
| 8. |
|
|
| 9. |
- Lindgren, Ingvar, 1931, et al.
(författare)
-
Combining Many-Body Perturbation and Quantum Electrodynamics
- 2011
-
Ingår i: Journal of Atomic, Molecular and Optical Physics. - : Hindawi Limited. - 1687-9228 .- 1687-9236. ; 2011
-
Tidskriftsartikel (refereegranskat)abstract
- It has been a long-sought problem to be able to combine many-body perturbation theory and quantum-electrodynamics into a unified, covariant model. Such a model has recently been developed at our laboratory and is outlined in the present article. The model has potential applications in many areas and opens up the possibility of studying the interplay between various interactions in different system. The model has so far been applied to highly-ionized heliumlike ions, and some numerical results are given. It is expected that the combined effect---that has never been calculated before---could have a significant effect on certain experimental data.
|
|
| 10. |
- Lindgren, Ingvar, 1931, et al.
(författare)
-
Combining quantum electrodynamics and electron correlation
- 2015
-
Ingår i: Nuclear Physics: Present and Future. - Cham : Springer. - 9783319101996 ; , s. 287-295
-
Bokkapitel (refereegranskat)abstract
- There is presently a large interest in studying highly charged ions in order to investigate the effects of quantum-electrodynamics (QED) at very strong fields. Such experiments can be performed at large accelerators, like that at GSI in Darmstadt, where the big FAIR facility is under construction. Accurate experiments on light and medium-heavy ions can also be performed by means of laser and X-ray spectroscopy. To obtain valuable information, accurate theoretical results are required to compare with. The most accurate procedures presently used for calculations on simple atomic systems are (i) all-order many-body perturbative expansion with added first-order analytical QED energy corrections, and (ii) two-photon QED calculations. These methods have the shortcoming that the combination of QED and correlational effects (beyond lowest order) is completely missing. We have developed a third procedure, which can remedy this shortcoming. Here, the energy-dependent QED effects are included directly into the atomic wave function, which is possible with the procedure that we have recently developed. The calculations are performed using the Coulomb gauge, which is most appropriate for the combined effect. Since QED effects, like the Lamb shift, have never been calculated in that gauge, this has required some development. This is now being implemented in our computational procedure, and some numerical results are presented. © Springer International Publishing Switzerland 2015.
|
|
