
On the square of first order differential operators of Dirac type and the Einstein–Hilbert action
Keywords: 53C05; 53C07; 70S05; 70S15; 83C0502.40.Hw; 02.40.Ma; 04.20.-q; 14.80.BnDirac bundles; Dirac type differential operators; Linear connections; General relativity; Gauge theories; Standard Model