Principal Symbol of Euler-Lagrange Operators
  We shall introduce the principal symbol for Euler-Lagrange operators and use them to charac- terise well-posed initial value problems. We shall clarify how constraints can arise in Lagrangian covariant theories by extending the standard treatment in GR. Finally, we sketch a quantization procedure based on what done in LQG. 
Lorenzo Fatibene, Simon Garruto
gr-qc math-ph math.MP