sluttilstanden

In physics, sluttilstanden refers to the condition of a system after a process has completed. It describes the particles, fields, energies and quantum numbers that remain once interactions cease, and contrasts with the initial state before the process began as well as any transient intermediate states that may occur during the interaction. In Scandinavian physics literature, sluttilstanden is used to denote the final state, literally translated as “the final state.”

In quantum mechanics and quantum field theory, the final state is treated as the asymptotic configuration of outgoing particles after the interaction region. Transition probabilities are computed for going from an initial state to a final state using the S-matrix or reaction amplitudes; conservation laws fix the possible final states in terms of energy, momentum, angular momentum, and other quantum numbers.

In scattering experiments, the final state is what detectors observe. The cross section for a process is obtained by summing over all allowed final states, each weighted by its probability. Phase space describes the kinematically allowed configurations of the final-state particles given the total energy and momentum constraints.

In chemistry and nuclear physics, the term applies similarly: a final-state product arrangement after a reaction, decay, or collision. For example, electron-positron annihilation produces a final state of photons; beta decay yields a final state consisting of a daughter nucleus and emitted leptons or neutrinos. The concept is central to predicting and interpreting outcomes across many disciplines.