The Poincare Group

     The Poincare Group is the group that leaves invariant the interval in Minkowski spacetime.  It is the 'semidirect' product of translations in R^3 and 'boosts' written in terms of Lorentz transformations.  In quantum field theory we have to have our Lagrangian satisfy the symmetries given by this group if we're going to satisfy Special Relativity. 
     It's interesting to think about how we have to satisfy Special Relativity in a theory that includes entanglement. 

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