Roadmap

Note: This page is out of date. Latest revision in September 2017.

QED corrections to the Dirac equation come in following three flavors, which in turn can be implemented to various orders and/or using different methods.

• Vacuum polarization (VP)
  • Uehling (2nd order)
  • Källén-Sabry (KS; 4th order)
  • Wichmann-Kroll (WK)
• Self-energy (SE)
  • Hydrogenic (Mohr-type)
  • Flambaum
  • Shabaev
  • Pyykkoe
• Breit interaction
  • Frequency independent (Gaunt)
  • Full frequency-dependent Breit

Status in current Grasp2k master

All Grasp2k QED implementation is done in the rci program.

For VP, Grasp2k currently implements Uehling + KS. (Phys. Rev. A 13, 1283)

For SE, Grasp2k has the hydrogenic-type SE implemented. There is also an unused modernized implementation of the rci/fzalf.f90, which extends the tables with more recent publications.

rci also implements the Breit interaction in its full frequency-dependent glory.

Roadmap

• Port Pykkoe SE from NZ version of Grasp92
• Port Flambaum SE from NZ version of Grasp92
• Incorporate Shabaev SE routines
• Implement an API for the Breit equation
  • Strip out the existing Breit code from rci
  • Incorporate new API in rci
  • Incorporate the new API into the variational part.
• Move and clean up the VP routines from rci to the new library.
  • Including switching to the more modern fzalf.f90 implementation.
• Move and clean up the Mohr SE routines from rci to the new library.
• Implement Wichmann-Kroll VP

From a technical point of view, the QED code will be organized as a separate library (under lib/qed), that will be compiled into a static library and then linked against executable when necessary. It will provide a generic API that could be used in different parts of Grasp2k code.

The routines will be documented using Doxygen inline syntax.

Current progress

Nothing has been merged so far, but various parts of the implementation live on different branches:

• Existing Mohr routines have been moved. Also, Pyykkö and Flambaum routines have been ported over to grasp2k. (mp/qed-potentials branch.)
• Shabaev routines have been modified and incorporated. Explicit permission from the QEDMOD authors is still necessary before it can be merged into master and distributed. (mp/qed-shabaev branch)