Lecture 23, 18.300, Thu Apr 28, 2022.
Topic: Eikonal equation and Rays, Generalizations, Bi-characteristics and
       correspondence principle in QM.
% --------------------------------------------------------------------------
1-Derive/motivate Plancherel's equality for the Fourier Transform.
2-Relationship between FT and uncertainty principle in QM.
3-Derive the Eikonal equation for wave-fronts propagating normal to
  themselves at speed c = c(x) > 0.
4-Write characteristic equations for the Eikonal.
%
% ==========================================================================
NOTE: Here #nnn	are references to the Lecture Points file.
      [PSQ] means Problem Set Question.
 The "lecture summaries and points" are NOT intended as study materials.
 The points purpose is explained in the "lecture points" file.
 The summaries are brief descriptions each lecture, used by the instructor
 to keep track of the material covered. They ARE *NOT* "lecture notes" to
 be used to study and/or replace attending the lectures, etc. They are
 provided for your convenience, as a help to organize your own notes.
% ==========================================================================
% EOF