Supersymmetric Standard Models on D-Branes

Abstract

Type IIB superstring models with the standard model gauge group on D3-branes and with massless matter associated with open strings joining D3-branes to D3-branes or D3-branes to $\mathrm{D}{7}_3$-branes are studied. Models with gauge coupling constant unification at an intermediate scale between about $10^{10}$ and $10^{12}$GeV and consistency with the observed value of ${\sin }^2{\theta }_W(M_Z)$ are obtained. Extra vector-like states and extra pairs of Higgs doublets play a crucial role.

Comments: 10 pages, LaTeX file, version to appear in Phys.Lett.B