title: Birkhoff's theorem
text: # Birkhoff's theorem
  
  Birkhoff's theorem may refer to several theorems named for the American mathematician George David Birkhoff:
  
  * Birkhoff's theorem (relativity)
  * Birkhoff's theorem (electromagnetism)
  * Birkhoff's ergodic theorem
  
  It may also refer to theorems named for his son, Garrett Birkhoff:
  
  * Birkhoff–von Neumann theorem for doubly stochastic matrices
  * Birkhoff's HSP theorem, concerning the closure operations of homomorphism, subalgebra and product
  * Birkhoff's representation theorem for distributive lattices
  * Birkhoff's theorem (equational logic), stating that syntactic and semantic consequence coincide
  