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Von Neumann Group Algebra




Two basic examples of von Neumann algebras are as follows. The ring ''L''(R) of essentially bounded measurable functions on the real line is a commutative von Neumann algebra, which acts by pointwise multiplication on the Hilbert space ''L''2(R) of square integrable functions. The algebra ''B''(''H'') of all bounded operators on a Hilbert space ''H'' is a von Neumann algebra, non-commutative if the Hilbert space has dimension at least 2.

von Neumann algebras, under the original name of rings of operators, were first studied by von Neumann in 1929; he and Francis Murray developed the basic theory in a series of papers starting in 1936.


DEFINITIONS


There are three common ways to define von Neumann algebras.

  • algebras of bounded operators (on a Hilbert space) containing the identity. In this definition the weak (operator) topology can be replaced by almost Any Other Common Topology other than the norm topology,

  • algebras of bounded operators that are closed in the norm topology are C--- Algebra s, so in particular any von Neumann algebra is a

  • algebra.)




  • algebras that have a Predual ; in other words the von Neumann algebra, considered as a Banach space, is the dual of some other Banach space called the predual. The predual of a von Neumann algebra is unique up to isomorphism.

  #The Predual Of The Von Neumann Algebra ''B''(''H'') Of Bounded Operators On A Hilbert Space ''H'' Is The Banach Space Of All "http://wwwinformationdelightinfo/information/entry/trace_class" class="copylinks">Trace Class operators with the trace norm ''A''= Tr(''A'') The Banach space of trace class operators is itself the dual of the C-algebra of compact operators (which is not a von Neumann algebra)