Eugene Tracy at MSRI - Ray helicity: A geometric invariant for multi-dimensional resonant linear wave conversion

<BODY> MSRI Streaming Video Series <BR> Eugene Tracy - Ray helicity: A geometric invariant for multi-dimensional resonant linear wave conversion <BR> <center> A PDF version of the lecture notes is available <A HREF="http://www.msri.org/publications/ln/msri/2003/semiclassical/tracy/1/meta/aux/tracy.pdf">here</A>. </center> </BODY>