On the full bosonic string from Minkowski space to Riemannian manifolds
  We study the action of the full bosonic string for the domain being two-dimensional Minkowski space and the target a Riemannian manifold. Its critical points couple the wave map equation to a scalar and a two-form potential. Besides investigating their basic features we establish existence results for the latter. 
Volker Branding
math.DG math-ph math.AP math.MP