Recent content by Bobdemaths

OK I found the answer. To get rid of the derivatives of Dirac deltas, I used the identity f(x) \delta ' (x-y) = f(y) \delta ' (x-y) - f'(x) \delta (x-y) which follows from the convolution between delta and (f \times \varphi)' (\varphi is a test function). This also produces the remaining wanted...

Hi, Suppose you have a collection of fields \phi^i (t,x) depending on time and on 1 space variable, for i=1,...,N. Its dynamics is defined by the Lagrangian L=\frac{1}{2} g_{ij}(\phi) (\dot{\phi}^i \dot{\phi}^j - \phi ' ^i \phi ' ^j ) + b_{ij}(\phi) \dot{\phi}^i \phi ' ^j where...