Hi,there! Here is the lagrangian for a charged scalar field http://www.photodump.com/direct/Bbking22/P-meson-Lagrangian.jpg [Broken] as it can be found in “the large scale structure of space-time” Hawking, Ellis on page 68. It seem’s that I have problem varying Aa on the lagrangian because I get http://www.photodump.com/direct/Bbking22/P-meson-Myresult.jpg [Broken] , while the result of the book is http://www.photodump.com/direct/Bbking22/P-meson-AmVar.jpg [Broken] . Does anyone have the same problem? Does anyone gets the book’s result? Thanks for the help. Here are all the results for this example http://www.photodump.com/direct/Bbking22/Example3.jpg [Broken] .