Stretched strings and worldsheets with a handle

In the presence of the constant background NS two-form gauge field, we cons truct the worldsheet partition functions, bulk propagators and boundary pro pagators for the worldsheets with a handle and a boundary. We analyze the n oncommutative phi (3) field theory amplitudes that correspond to the genera l two-point insertions on the two-loop nonplanar vacuum bubble. By the dire ct string theory amplitude computations on the worldsheets with a handle, w hich reduce to the aforementioned field theory amplitudes in the decoupling limit, we find that the stretched string interpretation remains valid for the types of amplitudes in consideration. This completes the demonstration that the stretched string picture holds up in the general multiloop context . (C) 2001 Elsevier Science B.V. All rights reserved.