Finite Strings From Non-Chiral Mumford Forms
  We show that there is an infinite class of partition functions with world-sheet metric, space-time coordinates and first order systems, that correspond to volume forms on the moduli space of Riemann surfaces and are free of singularities at the Deligne-Mumford boundary. An example is the partition function with 4=2(c_2+c_3+c_4-c_5) space-time coordinates, a $b$-$c$ system of weight 3, one of weight 4 and a beta-gamma system of weight 5. Such partition functions are derived from the mapping of the Mumford forms to non-factorized scalar forms on M_g introduced in arXiv:1209.6049. 
Marco Matone
hep-th math.AG