$M$-theory dynamics on a manifold of $G_2$ holonomy

We analyze the dynamics of M-theory on a manifold of G2 holonomy that is developing a conical singularity.The known cases involve a cone on CP 3 , where we argue that the dynamics involves restoration of a global symmetry, SU(S)/U(1) 2 , where we argue that there are phase transitions among three possible branches corresponding to three classical spacetimes, and S 3 x S 3 and its quotients, where we recover and extend previous results about smooth continuations between different spacetimes and relations to four-dimensional gauge theory.