On Measuring Distances in the Quantum Gravity Landscape

Abstract: In this note, we propose a generalized notion of distance between vacua in the theory of a scalar field $\phi$ with scalar potential $V(\phi)$ coupled to gravity. We propose the normalized tension of domain wall connecting different field values, with a varying normalization relative to a local energy scale, as the distance. We show this definition reproduces the usual moduli space distance for zero potential, as well as the $d\propto |\log \Lambda|$ behavior with the vacuum energy $\Lambda$ in the AdS case, previously proposed in the literature. In the case of large AdS we also obtain the expected exponent of mass versus distance in one particular case, when the mass of the light tower is $m\sim \sqrt \Lambda$ and there is a single extra dimension decompactifying. We also discuss the features and shortcomings of alternative but related proposals.