Is spacetime absolutely or just most probably Lorentzian?

Abstract

Pre-gauging the cosmological scale factor a(t) does not introduce unphysical degrees of freedom into the exact FLRW classical solution. It seems to lead, however, to a non-dynamical mini superspace. The missing ingredient, a generalized momentum enjoying canonical Dirac (rather than Poisson) brackets with the lapse function n(t), calls for measure scaling which can be realized by means of a scalar field. The latter is essential for establishing a geometrical connection with the five-dimensional Kaluza–Klein Schwarzschild–deSitter black hole. Contrary to the Hartle–Hawking approach, (i) the t-independent wave function is traded for an explicit t-dependent , (ii) the classical FLRW configuration does play a major role in the structure of the ’most classical’ cosmological wave packet, and (iii) the non-singular Euclid/Lorentz crossovers get quantum mechanically smeared.