Ramification of inseparable coverings of schemes and application to   diagonalizable group actions
  We define the notion of inseparable coverings of schemes and we propose a ramification formalism for them, along the lines of the classical one. Using this formalism we prove a formula analogous to the classical Riemann-Hurwitz formula for generic torsors under infinitesimal diagonalizable group schemes. 
Gabriel Zalamansky
math.AG