# Simple Physical Pictures for Radiative Processes Vacuum Fluctuations versus Radiation Reaction

## Abstract

Radiative processes, such as spontaneous emission or radiative corrections (Lamb-shift, g-2), are usually described as resulting from the interaction of the electron with the quantum vacuum field (vacuum fluctuations), or with the self field of the electron (radiation reaction).

The first lecture, which is essentially a presentation of the results derived in reference [1], is devoted to the identification and to the discussion of the respective contributions of vacuum fluctuations and radiation reaction. The calculations are based on non relativistic Heisenberg equations (lowest order in 1/c). Spin and magnetic effects are neglected. Connections are established with quantum theory of damping and linear response theory.

The second lecture, which is essentially a presentation of the results derived in reference [2], extends the physical discussion of lecture 1 by including spin and magnetic affects and relativistic corrections. An effective hamiltonian, describing radiative corrections and valid up to order (1/c)^{2}, is derived for an electron moving slowly in external static fields. The positive sign of the spin anomaly g-2 is physically interpreted. Finally, a sketch of a completely relativistic calculation of g-2 is presented [3], allowing a discussion of the contribution to g-2 of the relativistic modes of the radiation field.

### References

- [1]J. DALIBARD, J. DUPONT-ROC and C. COHEN-TANNOUDJI J. Physique 43, 1617 (1982)CrossRefGoogle Scholar
- [2]J. DUPONT-ROC, C. FABRE and C. COHEN-TANNOUDJI J. Phys. B 11, 563 (1978) see also same authors + P. AVAN J. Physique 37, 993 (1976)ADSGoogle Scholar
- [3]J. DUPONT-ROC and C. COHEN-TANNOUDJI To appear 3n “New Trends in Atomic Physics ”, Les Houches 1982 Session XXXVIII, STORA R. and GRYNBERG G. ed. (North Holland, Amsterdam )Google Scholar