Unification on gauge invariance and relativity
  The inconsistence of Dirac-Weyl field equations with the universal U(1) gauge invariance of neutrinos in quantum mechanics led to generalize the special relativity to the generic relativity, which was composed of the special relativity and its three analogues with different signatures of metrics. The combination of the universal U(1) gauge invariance and the generic relativity naturally deduced the strong gauge symmetries $% SU(3)$ and the electroweak ones $SU(2)\times U(1)$ in the Standard Model. The universal U(1) gauge invariance of elementary fermions is attributed to its nature of complex line in three dimensional projective geometry. 
Haigang Lu