Book contents
- Frontmatter
- Contents
- Preface
- 1 The classical electromagnetic field in the absence of sources
- 2 The quantum electromagnetic field in the absence of sources
- 3 The quantum matter field
- 4 Electrodynamics in the presence of sources
- 5 Atoms dressed by a real e.m. field
- 6 Dressing by zero-point fluctuations
- 7 Energy density around dressed atoms
- 8 Further considerations on the nature of dressed states
- Appendix A Multipolar expansion for the vector potential
- Appendix B Electric polarization and magnetization of the Schrödinger field
- Appendix C Rayleigh-Schrödinger perturbation theory
- Appendix D Sum rules for the nonrelativistic hydrogen atom
- Appendix E From Gauss system to SI
- Appendix F Gauge invariance and field interactions
- Appendix G Dressed sources in relativistic QED and in QCD
- Appendix H The energy-momentum tensor and Lagrangian density
- Appendix I The dressed relativistic hydrogen atom
- Appendix J The nonrelativistic Lamb shift in a hydrogenic atom
- Index
8 - Further considerations on the nature of dressed states
Published online by Cambridge University Press: 12 November 2009
- Frontmatter
- Contents
- Preface
- 1 The classical electromagnetic field in the absence of sources
- 2 The quantum electromagnetic field in the absence of sources
- 3 The quantum matter field
- 4 Electrodynamics in the presence of sources
- 5 Atoms dressed by a real e.m. field
- 6 Dressing by zero-point fluctuations
- 7 Energy density around dressed atoms
- 8 Further considerations on the nature of dressed states
- Appendix A Multipolar expansion for the vector potential
- Appendix B Electric polarization and magnetization of the Schrödinger field
- Appendix C Rayleigh-Schrödinger perturbation theory
- Appendix D Sum rules for the nonrelativistic hydrogen atom
- Appendix E From Gauss system to SI
- Appendix F Gauge invariance and field interactions
- Appendix G Dressed sources in relativistic QED and in QCD
- Appendix H The energy-momentum tensor and Lagrangian density
- Appendix I The dressed relativistic hydrogen atom
- Appendix J The nonrelativistic Lamb shift in a hydrogenic atom
- Index
Summary
Introduction. In this final chapter we review two topics of the literature concerning dressed atoms which are of conceptual relevance and capable of shedding some light on the physical meaning and significance of atomic dressing. The first section is devoted to some recent work in connection with the quantum theory of measurement. We include the measuring apparatus in the Hamiltonian along with an appropriate apparatus-atom coupling. We argue that the theory of measurement of finite duration provides us with a tool for detecting the spectral composition of the virtual cloud surrounding an atom. In fact, we show that in a measurement of duration T on a two-level atom fully dressed by the vacuum fluctuations, as discussed in Chapters 6 and 7, the apparatus perceives the atom as dressed only by photons of frequency larger than T-1. In the case of a two-level atom dressed by a single-mode field populated by real photons, discussed in Chapter 5, we show that if T is smaller than the inverse Rabi frequency ħΔ-1, the atom is perceived by the apparatus as bare; on the contrary, if T is larger than ħΔ-1, the atom is perceived as dressed. The time scales for the two cases of dressing, by vacuum fluctuations or by a real single-mode field, are very different, but the similarity of the effects indicates a common physical aspect of the two kinds of dressing.
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- Atom-Field Interactions and Dressed Atoms , pp. 275 - 309Publisher: Cambridge University PressPrint publication year: 1995