Physics:Quantum Scattering matrix
The Quantum scattering matrix, or S-matrix, is a mathematical object that relates incoming quantum states before an interaction to outgoing states after the interaction. It is widely used in scattering theory, particle physics, nuclear physics, and quantum field theory.[1]
ScholarlyWiki also has the related page Quantum S-matrix. This page gives the broader conceptual entry point, while the S-matrix page can hold more formal details, examples, and field-theory notation.
Incoming and outgoing states
In scattering problems, particles or waves begin in a prepared incoming state, interact in a finite region, and are later detected in outgoing channels. The scattering matrix encodes the amplitudes for each allowed transition.
Probabilities are obtained from the squared magnitudes of these amplitudes, while phases encode interference and resonance information.
Role in quantum theory
The scattering matrix is important because many experiments observe particles long before and long after an interaction, not during the interaction itself. Collider events, atomic collisions, and wave scattering can all be organized in this language.
In quantum field theory, the S-matrix is constrained by unitarity, symmetry, causality, and conservation laws. It connects naturally with Feynman diagrams and perturbation theory.
See also
- Physics:Quantum Scattering theory
- Physics:Quantum S-matrix
- Physics:Quantum Feynman diagrams
- Physics:Quantum Path integral formulation
References
- ↑ "S-matrix". Wikipedia. https://en.wikipedia.org/wiki/S-matrix.
Source attribution: Physics:Quantum Scattering matrix