Hello, this is the first time i'm sending a message and i don't know so good the procedure. Please forgive me for my english but i'm from greece, thus i am not experienced in speaking english, but i'll try to be as plain as i can. I'd like to ask something about electromagnetic waves. I'm looking some information about negative diffraction. I've searched the web for any articles or relative papers, but i couldn't find anything. Have you got any idea where i can search or if you can help me by sending the form of Poynting's vector and the relative between wave propagation and energy fluency on this case?Or the form of Maxwell's equation in this case? Thank you for your patience.