kvantelektrodynamikens

Kvantelektrodynamikens, often abbreviated as QED, is a quantum field theory that describes the interactions between light and matter. It is the quantum theory of electromagnetism, detailing how electrically charged particles, such as electrons and positrons, interact by exchanging photons. QED is renowned for its extraordinary predictive accuracy, making it one of the most precisely tested theories in physics.

The foundation of QED lies in the concept of quantized fields. Instead of treating particles as fundamental entities, QED views them as excitations of underlying quantum fields. For electromagnetism, these fields are the electron field and the photon field. Interactions occur when these fields exchange quanta, which are the fundamental particles of the field. In QED, the photon is the quantum of the electromagnetic field, mediating the electromagnetic force.

Key features of QED include the concept of virtual particles. When charged particles interact, they can temporarily emit and reabsorb virtual photons. These virtual particles are not directly observable but are crucial for the calculations that accurately predict observable phenomena. Perturbation theory is a common mathematical tool used in QED to calculate the probabilities of various interactions by considering these exchanges of virtual particles.

QED successfully explains a wide range of phenomena, including the Lamb shift in atomic energy levels, the anomalous magnetic dipole moment of the electron, and the creation and annihilation of electron-positron pairs. Its development involved the contributions of many physicists, including Richard Feynman, Julian Schwinger, and Shin'ichirō Tomonaga, who shared the Nobel Prize in Physics in 1965 for their work on QED. QED serves as a paradigm for other quantum field theories, such as quantum chromodynamics (QCD).