From: r_delaney2001@yahoo.com   
      
   On July 16, 2015 Phil Hobbs wrote:   
   > > Recently, I attended a seminar of Hamilton's cone, or   
   > > whatever it's called, inside crystals.   
   > > Apparently, research continues on this phenomenon,   
   > > there's still new stuff to uncover.   
   > >   
   > > At one point, the speaker said, "the direction of energy flow   
   > > is different than the wave direction."   
   > > ??   
   > > If I recall correctly, the wave direction is given   
   > > by the Poynting vector (the most mnemonic label in   
   > > science):  E x H.  Am I now to believe the power   
   > > doesn't flow the same way?   
   >   
   > You have to be careful about your terms.  Phase propagates as usual,   
   > exp(i k x - omega t) for a plane wave.  However, in an anisotropic   
   > crystal, the main part of the optical power doesn't necessarily   
   > propagate along k.   
      
   No doubt you're right, but I don't get it.  It's partly   
   a matter of semantics - I don't grok the difference   
   between 'phase propagation', 'wave propagation', and   
   'energy propagation'   
      
   My memory of the physics, is that at a particular point   
   and moment,  the field is represented by a 6-vector   
   (3 x E, 3 x H), and the energy is given by E x H.   
   That vector then 'travels', loosely speaking, to the   
   neighboring point; hence velocity.  I don't understand   
   how that could differ from energy flow (or optical power flow).   
      
   --   
   Rich   
      
   --- SoupGate-Win32 v1.05   
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