Local Expansion Mechanisms for Quantum-Scale Wormholes

Abstract: Models of quantum spacetime that are consistent with quantum energy inequalities potentially enable the formation of Planck scale wormholes. Building on the proposal of Morris, Thorne, and Yurtsever that such microscopic spacetime structures might be enlarged to macroscopic size, we revisit Roman's analysis of a wormhole in an inflationary de Sitter background. In this context, we introduce a refined quasi-local toy mechanism, which we call the local inflation bubble. This construction inflates a compact region of spacetime and thereby magnifies the underlying microstructure. Using the Einstein equations we determine the required stress-energy to sustain the bubble and obtain intrinsic lower bounds for the corresponding energy density, while acknowledging the continued reliance on exotic matter.