Page "Renormalization" Paragraph 91

In QFT, the value of a physical constant, in general, depends on the scale that one chooses as the renormalization point, and it becomes very interesting to examine the renormalization group running of physical constants under changes in the energy scale.

The coupling constants in the Standard Model of particle physics vary in different ways with increasing energy scale: the coupling of quantum chromodynamics and the weak isospin coupling of the electroweak force tend to decrease, and the weak hypercharge coupling of the electroweak force tends to increase.

At the colossal energy scale of 10 < sup > 15 </ sup > GeV ( far beyond the reach of our current particle accelerators ), they all become approximately the same size ( Grotz and Klapdor 1990, p. 254 ), a major motivation for speculations about grand unified theory.

Instead of being only a worrisome problem, renormalization has become an important theoretical tool for studying the behavior of field theories in different regimes.