Towards Full ‘Galilei General Relativity’: Bargmann-Minkowski and Bargmann-Galilei Spacetimes

Galilei-Newton spacetime $$\mathbb {G}$$ with its Galilei group can be understood as a ‘degeneration’ $$c \rightarrow \infty $$ of Minkowski {M}$$ Poincaré group. does not have metric and symmetry transformations do include energy; but Bargmann-Galilei $$B\mathbb , 5-dimensional extension that preserves physics, remedies these infelicities. Here an analogous Bargmann-Minkowski is described. While necessary for it may illuminate path towards more extensive ‘Galilei general relativity’ than presently known, which would useful—and conceptually mathematically sound—approximation in astrophysical scenarios such core-collapse supernovae.