Realization of heterotic objects explaining Green–Rudra Shenker effects

Determine how the ten-dimensional SemiSpin(32) (HO) and (E8 × E8) ⋊ Z2 (HE) heterotic string theories realize the non-perturbative extended objects suggested by the non-trivial homotopy of their gauge groups that would account for the e^{-1/g_s} Shenker-effect contributions to the R^4 term reported by Green and Rudra.

Background

The paper reviews Shenker’s argument predicting non-perturbative corrections of order e^{-1/g_s} in closed string theories and highlights Green and Rudra’s results showing such effects in the 10D HO theory’s R^4 term, but not in 10D HE unless compactified with a Wilson line.

The authors note that homotopy groups of the heterotic gauge groups indicate the existence of candidate objects, yet their concrete realization within the heterotic theories has remained unclear, motivating the work presented in this Letter.