Symmetries of the QCD

An important feature of the QCD is the conspicuous amount of symmetries of its lagrangian. First and foremost, its lagrangian is invariant under local gauge transformations, i.e. one can redefine the quark fields indipendently at every point in the space-time, without changing the physical content of the theory. This determines a number of implications in … Continue reading Symmetries of the QCD

Supersymmetry Breaking

Supersymmetry in the equation for the MSSM Lagrangian is an exact symmetry. This implies the mass degeneration for the components of each supermultiplet. Anyway, if the superparticles had the same masses of the respective particles, they would have already been observed and the Supersymmetry should therefore be broken. Although it is widely believed that a … Continue reading Supersymmetry Breaking


Fields with physical significance are those that verify the Euler--Lagrange equations, or that satisfy the Hamilton's principle. For such systems, a general and systematic procedure is available to establish conservation theorems and constants of motion, as a consequence of invariance properties. Thus, conservation laws and selection rules observed in Nature may be imposed as symmetries of … Continue reading Symmetries