Universal Torsion-Induced Interaction from Large Extra Dimensions

We consider the Kaluza-Klein (KK) scenario in which only gravity exists in the bulk. Without the assumption of symmetric connection, the presence of brane fermions induces torsion. The result is a universal axial contact interaction that dominates those induced by KK gravitons. This enhancement arises from a large spin density on the brane. Using a global fit to $Z$-pole observables, we find the $3\sigma$ bound on the scale of quantum gravity to be 28 TeV for $n=2\mathrm{}$. If Dirac or light sterile neutrinos are present, the data from SN1987A increase the bound to $\sqrt{n}{M}_S\ge 210\mathrm{TeV}$.