String-Like Dual Models for Scalar Theories
  We show that all tree-level amplitudes in $\varphi^p$ scalar field theory can be represented as the $\alpha'\to0$ limit of an $SL(2,R)$-invariant, string-theory-like dual model integral. These dual models are constructed according to constraints that admit families of solutions. We derive these dual models, and give closed formulae for all tree-level amplitudes of any $\varphi^p$ scalar field theory. 
Christian Baadsgaard, N. E. J. Bjerrum-Bohr, Jacob L. Bourjaily, and   Poul H. Damgaard
hep-th