Schild's Ladder

Cass has stumbled on something that might be an entirely different type of physics, and she's travelled three hundred and fifty light-years to Mimosa Station, a remote experimental facility, to test her theory. The novo-vacuum she creates is predicted to begin decaying the instant it's created, but even so short-lived a microscopic speck could shed new light on the origins of the universe.

But instead of decaying, Cass's novo-vacuum is wildly successful and begins expanding, slowly but inexorably taking over the universe ...