A method to prove the minimality of the order p6 chiral Lagrangian

In this talk, a method to find relations between the operators in the the mesonic Lagrangian of Chiral Perturbation Theory at order p6 is presented, which can be used to establish the minimality of the Lagrangian operator basis. As an example, we apply the method to the two-flavour case in the absence of scalar and pseudo-scalar sources (s=p=0), and conclude that the minimal Lagrangian contains 27 independent operators.