Gravitational form factors in QED and Yukawa model

One of most outstanding problem in Quantum Chromodynamics (QCD) is to study the internal structure of hadrons i.e. to determine the spectrum and structure of hadrons in terms of their quark and gluon degrees of freedom.The spin-flip matter form factor receives contribution from fermion and boson constituents. This was proved that anomalous gravitomagnetic moment coupling B(0) to gravity vanish for any composite system. Classically, this result was derived from the equivalence principle and from the conservation of the energy-momentum tensor