Semiclassical physics

A Semiclassical approximation in quantum physics considered only one part of the system quantum mechanically, while external fields are classically described as constant changing or when. As a rule, it is about a development in powers of the Planck constant, with classical physics in the potency of 0 results and the first non-trivial approximation to the power of (-1). In this case, there is a clear link between the quantum mechanical system and the associated semi-classical or classical approximations, as it results analogy in optics in the transition from wave optics to geometrical optics ( Eikonalnäherung ).

Examples of a semiclassical approximation,

• The WKB approximation in quantum mechanics
• Quantum field theory in embedding this theory in the gravitational physics, in quantum field theory - the quantum mechanical theory par excellence - is considered within the true curved, but classical space -time theory (eg, generally in the classical Einstein's theory of relativity )

In quantum field theory, Feynman diagrams are only in the semiclassical approximation, with a maximum of a closed loop taken into account (this corresponds precisely to the above powers of Planck's constant).

• Quantum physics