What is negative refraction?

    M.W. McCall, P. Kinsler, A. Favaro

    Blackett Laboratory, 
    Imperial College London,
    Prince Consort Road,
    London SW7 2AZ,
    United Kingdom.

    D. Censor
    Electrical & Computer Engineering Department
    Ben-Gurion University of the Negev, 
    Israel 


    SPIE Proceedings 7392, 73921M (2009); 
    ``Metamaterials: Fundamentals and Applications II'',
     eds. M.A. Noginov, N.I. Zheludev, A.D. Boardman, N. Engheta,

     http://spie.org/x648.html?product_id=827472
     http://dx.doi.org/10.1117/12.827472


We will review the current status of various intrinsic definitions of
negative refraction (i.e. negative phase velocity, or NPV, propagation
which has been variously ascribed to counter-position of (i) the group
velocity, (ii) the energy velocity, (iii) the Poynting Vector, with
the wave vector of a plane wave in a medium. A key result is that
simultaneously negative effective $\epsilon$ and $\mu$ can be achieved 
in a natural medium in motion. However, can this be said to result in 
observable phenomena?