How Heavy Can Moduli Be?

Abstract

In Kaluza-Klein (KK) compactification of gravitational theories, moduli fields, which are scalar fields associated to the deformations of the compact manifold, are typically lighter than the KK gravitons. However, a universal limit on their mass does not seem to exist. We provide numerical evidence that a light scalar particle, with mass ratio to the first KK graviton $(m_{\mathrm{sc}}/m_{1KK}{)}^2\le 4/3$, is necessary for the consistency of the $4d$ effective theory of KK gravitons. This can be interpreted as a limit on how rigidly the compact manifold can be stabilized.

11 pages