B.Baumgartner 
Postulates for Time-Evolution in Quantum Mechanics
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ABSTRACT.  A detailed list of postulates is formulated in an algebraic setting.
These postulates are sufficient to entail the standard time evolution
governed by the Schr\"odinger- or Dirac equation. They are also necessary 
in a strong sense: Dropping any one of the postulates allows for other
types of time-evolution, as is demonstrated with examples. Some
philosophical remarks shall hint on possible further investigations.