 Heterotic string

A string theory combining a bosonic left-moving system with a supersymmetric right-moving system. Ten target coordinates leave sixteen left-moving internal degrees of freedom for gauge currents. Modular consistency allows the familiar gauge algebras ${\mathfrak{e}}_8\oplus {\mathfrak{e}}_8$ and $\mathfrak{so}(32)$. Suitable compactification can produce spacetime supersymmetry and chiral gauge matter.