On energy-momentum and spin/helicity of quark and gluon fields

Understand

In special relativity, quantum matter can be classified according to mass-energy and spin.

• The corresponding field-theoretical notions are the energy-momentum-stress tensor T and the spin angular momentum tensor S.
• Since each object in physics carries energy and, if fermionic, also spin, the notions of T and S can be spotted in all domains of physics.
• We discuss the T and S currents in Special Relativity (SR), in General Relativity (GR), and in the Einstein-Cartan theory of gravity (EC).