1 Wave equation - initial displacement is box function 1 Proof of Huygens Principle 1 Where is the wild use of the Dirac delta function in physics justfied? 1 What do we do with the dummy variable in d'Alembert's wave equation? 1 Lighthill explanation of delta function/generalized functions

### Reputation (305)

 +5 Terminology: 'Definite' or 'Indefinite' integral? Wiki vs Visual Calculus +10 Dirac Delta distribution (function) confusion +10 Confused with a spherical coordinate system surface element +10 Proof of Huygens Principle

### Questions (15)

 2 Dirac Delta distribution (function) confusion 2 Confused with a spherical coordinate system surface element 2 Proper use of various derivative and partial derivative notations 2 Can all linear operators on functions be represented as a convolution of the input function with the operator's impulse response? 2 Can the Dirac Delta, $\delta$, be obtained by taking the limits of a rectangular pulse?

### Tags (38)

 4 dirac-delta × 15 1 mathematical-physics × 3 3 pde × 5 1 wave-equation × 3 1 distribution-theory × 8 1 definition × 2 1 functional-analysis × 5 1 fourier-analysis 1 reference-request × 3 1 math-history