# What does off-diagonal term mean?

1. Jan 6, 2009

when we apply Higgs mechanism to the lagrangian of a complex scalar field... we get terms for a Glodstone boson, a massive scalar and a massive vector field in the new lagrangian..

we also get other terms.. one of them takes following form

$$A_\mu \partial^\mu \xi$$

this term is said to be off-diagonal in the fields... what does this mean? and what does it imply?

I mean how can we know just by looking at such a term that our lagrangian does not describe physical fields? and that we need to rewrite the lagranigan in terms of real fields... until we get the lagrangian which contains a massive vector and a massive scalar (Higgs particle)..

Last edited: Jan 6, 2009