Low-Scale Closed Strings and their Duals
I. Antoniadis, B. Pioline
TL;DR
The paper investigates how large extra dimensions and a low fundamental string scale can be realized in four-dimensional, weakly coupled Type II string theories, showing that TeV-scale strings with all internal dimensions at TeV can coexist with a suppressed gravitational coupling. It identifies two novel Type II realizations: in Type IIA, TeV-scale internal radii with gauge KK modes as the main signature and no TeV-scale gravity, and in Type IIB, two TeV dimensions with an intermediate gravity scale around $10^{11}$ GeV, where gravity becomes strong and a tensionless six-dimensional theory emerges at low energies. The authors leverage heterotic–Type I–Type II dualities and an M-theory framework to provide perturbative descriptions of large dimensions in the heterotic string, establishing a triality that connects the Type II scenarios to heterotic configurations with one or two large dimensions. These results offer a coherent picture linking different string theories through dualities and highlight potential experimental signatures and theoretical mechanisms for large extra dimensions at weak coupling.
Abstract
We study large dimensions and low string scale in four-dimensional compactifications of type II theories of closed strings at weak coupling. We find that the fundamental string scale, together with all compact dimensions, can be at the TeV, while the smallness of the string coupling accounts for the weakness of gravitational interactions. This is in contrast to the situation recently studied in type I theories, where the string scale can be lowered only at the expense of introducing large transverse dimensions felt by gravity only. As a result, in these type II strings, there are no strong gravity effects at the TeV, and the main experimental signature is the production of Kaluza-Klein excitations with gauge interactions. In the context of type IIB theories, we find a new possibility providing a first instance of large non-transverse dimensions at weak coupling: two of the internal dimensions seen by gauge interactions can be at the TeV, with the string scale and all other dimensions at intermediate energies of the order of $10^{11}$ GeV, where gravity becomes also strong. Finally, using duality, we provide a perturbative description for the generic case of large dimensions in the heterotic string. In particular, we show that the two type II theories above describe the cases of one and two heterotic large dimensions. A new M-theory derivation of heterotic-type II duality is instrumental for this discussion.