New variational principle for the Vlasov-Maxwell equations

A new Eulerian variational principle is presented for the Vlasov-Maxwell eq uations, This principle uses constrained variations for the Vlasov distribu tion in eight-dimensional extended phase space. The standard energy-momentu m conservation law is then derived explicitly by the Noether method. This n ew variational principle can be applied to various reduced Vlasov-Maxwell e quations in which fast time scales have been asymptotically eliminated (e.g ., low-frequency gyrokinetic theory).