Renormalisaatiovirta

Renormalisaatiovirta is a concept in quantum field theory that describes how the parameters of a theory, such as coupling constants and masses, change with the energy scale at which they are measured. This dependence arises because quantum corrections introduce infinities into calculations, and renormalization is a procedure to absorb these infinities into redefinitions of the parameters. The renormalization group equations govern how these parameters evolve.

The flow of these parameters under changes in energy scale is often visualized as a "flow" on a multi-dimensional space of couplings. Different points in this space represent different possible quantum field theories. The renormalization group flow describes how one theory can smoothly transition into another as the energy scale is varied. For instance, at high energies, a theory might appear to be governed by one set of parameters, while at low energies, it might behave as if it were described by a completely different set.

This concept is crucial for understanding the behavior of fundamental forces and particles across a wide range of energies. It helps explain phenomena like asymptotic freedom in quantum chromodynamics, where the strong force becomes weaker at very high energies. Conversely, it can also describe how forces might become stronger at lower energies. The fixed points of the renormalization group flow represent fundamental theories that do not change their behavior with energy scale.