Geometric flow equations for the number of space-time dimensions

In this paper we consider new geometric flow equations, called D-flow, which describe the variation of space-time geometries under the change of the number of dimensions. The D-flow is originating from the non-trivial dependence of the volume of space-time manifolds on the number of space-time dimensions and it is driven by certain curvature invariants. We will work out specific examples of D-flow equations and their solutions for the case of D-dimensional spheres and Freund-Rubin compactified space-time manifolds. The discussion of the paper is motivated from recent swampland considerations, where the number D of space-time dimensions is treated as a new swampland parameter. (© 2021 The Authors. Fortschritte der Physik published by Wiley‐VCH GmbH)