Lattice QCD calculations

Due to the asymptotic freedom, the coupling constant of QCD is a diminishing function as the energy scale increases according to the following equation, already stated (*): . Therefore, the high-energy or equivalently the short-distance behavior can be described by a perturbative expansion, but a perturbative approach to the QCD fails at large distances where the begins to … Continue reading Lattice QCD calculations

The QCD phase diagram

A phase diagram aims to describe the behaviour of matter at different conditions depending for example from variables such as pressure and temperature. In the QCD phase diagram the interactions between particles are ruled by the quantum chromodynamics. The QCD phase transition scheme, in fact, is yet under studies and one of the targets of … Continue reading The QCD phase diagram

Colour confinement

The term confinement indicates that coloured free particles do not exist in Nature. Besides valence quarks, a hadron contains a population of more quarks and gluons. From the (b) side of the Figure in the previous post (*) it is possible to infer that the strong interaction between two quarks enhances with the increasing of their … Continue reading Colour confinement

Couplings and asymptotic freedom

Each of the four fundamental interactions can be characterized by a dimensionless parameter expressed in terms of universal constants, the coupling constant. In the lagrangian of strong interactions, the coupling constant is parameterized by the gauge coupling parameter,, giving in natural units . However, in a general field theory, the effective coupling constant is not a constant, … Continue reading Couplings and asymptotic freedom