Book contents
- Frontmatter
- Contents
- Preface
- Notes to the Preface
- Acknowledgements
- Notes to the Reader
- I Frame-setting essay
- 1 From quantum mechanics toward quantum electrodynamics
- 2 Second quantization
- 3 Photons and relativistic electrons
- 4 Quantum electrodynamics
- 5 Theories of the nuclear force in the 1930s
- Epilogue
- Notes
- References to the Frame-setting essay
- II Selected papers
- Index to Frame-setting essay
4 - Quantum electrodynamics
Published online by Cambridge University Press: 05 August 2012
- Frontmatter
- Contents
- Preface
- Notes to the Preface
- Acknowledgements
- Notes to the Reader
- I Frame-setting essay
- 1 From quantum mechanics toward quantum electrodynamics
- 2 Second quantization
- 3 Photons and relativistic electrons
- 4 Quantum electrodynamics
- 5 Theories of the nuclear force in the 1930s
- Epilogue
- Notes
- References to the Frame-setting essay
- II Selected papers
- Index to Frame-setting essay
Summary
Meanwhile, on 18 September 1931, Heisenberg wrote to Bohr that ‘my work seems to be somewhat gray on gray’ (Pauli, 1985). By 1931 the bright future for quantum physics that seemed just over the horizon in the fall of 1927 paled with the formulation of relativistic quantum mechanics. Besides the as yet uninterpreted negative energy states, there was the electron's divergent self-energy and the continuous energy spectrum of β-particles in the supposedly two-body final state of nuclear β-decay, which implied that energy was not conserved in nuclear reactions (Bohr, 1932) and that perhaps quantum mechanics was not valid within the nucleus (to be discussed in Chapter 5).
Measurement problems in a quantum theory of the electromagnetic field
At the 20–25 October 1930 Solvay Conference, Bohr, Dirac, Heisenberg and Pauli concurred that fundamental difficulties in quantum electrodynamics might be clarified by investigating measurability of electromagnetic field quantities. Upon his return to Copenhagen from Brussels, Bohr continued discussing field measurements with Lev Landau, who happened to be visiting at Bohr's institute. In December 1930 Landau went on to Zürich, where he interested Pauli's assistant Rudolf Peierls in field measurements. Their deliberations led to a joint 1931 publication entitled ‘Extension of the uncertainty principle to relativistic quantum theory’ (Landau and Peierls, 1931).
Measurement of an electric field can be accomplished through measuring the change in momentum of a charged test body placed in the field.
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- Chapter
- Information
- Early Quantum ElectrodynamicsA Sourcebook, pp. 41 - 83Publisher: Cambridge University PressPrint publication year: 1994