Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

Systems of charged particles (such as atomic nuclei and electrons) can be described by nonrelativistic quantum mechanics with the Coloumb interaction potential. A fully relativistic description is given by quantum electrodynamics which is much more complex.

Is it possible to expand various quantities in QED as power series in 1/c i.e. around the nonrelativistic approximation? Examples of relevant quantities are:

  • Ground state energy of a given set of charged particles
  • Excited state energies
  • Scattering cross sections of charged particles & their bound states (assuming we trace over the photons in the final state)
share|cite|improve this question
1  
Yes, it's possible. Look Breit equation, for example: en.wikipedia.org/wiki/Breit_equation – Vladimir Kalitvianski Dec 23 '11 at 12:45
1  
Valdimir, as your comment is providing an answer, could you post it as an answer? – Piotr Migdal Dec 23 '11 at 15:17

Yes, it's possible. Look Breit equation, for example: http://en.wikipedia.org/wiki/Breit_equation

share|cite|improve this answer
    
Thx Vladimir, this is indeed relevant to my question. However this only provides the answer to second order in 1/c. What about higher orders? – Squark Dec 23 '11 at 19:22
    
@Squark: Higher orders give radiation effects and cannot be reduced to non-relativistic potential terms depending solely on the inter-particle distances and velocities. They will include inevitably the propagating field variables. Do you want to include the radiated field too? – Vladimir Kalitvianski Dec 23 '11 at 22:07
    
@Squark: Normally for slow motions it is the dipole filed approximation which is dominant. You may be interested in the filed multipole expansions known from Classical Electrodynamics. – Vladimir Kalitvianski Dec 23 '11 at 22:20
    
well I want a computable expansion of the full QED. I didn't say it has to be reducible to potential terms – Squark Dec 24 '11 at 18:40

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.