Kaluza-Klein reduction on a maximally non-Riemannian space is moduli-free

Understand

We propose a novel Kaluza-Klein scheme which assumes the internal space to be maximally non-Riemannian, meaning that no Riemannian metric can be defined for any subspace.

• Its description is only possible through Double Field Theory but not within supergravity.
• We spell out the corresponding Scherk-Schwarz twistable Kaluza--Klein ansatz, and point out that the internal space prevents rigidly any graviscalar moduli.
• Plugging the same ansatz into higher-dimensional pure Double Field Theory and also to a known doubled-yet-gauged string action, we recover heterotic supergravity as well as heterotic worldsheet action.