Heterotic String

Abstract

A new type of superstring theory is constructed as a chiral combination of the closed $D=26$ bosonic and $D=10$ fermionic strings. The theory is supersymmetric, Lorentz invariant, and free of tachyons. Consistency requires the gauge group to be $\frac{\mathrm{Spin}(32)}{{Z}_{2}}$ or ${E}_{8}\ifmmode\times\else\texttimes\fi{}{E}_{8}$.