Abstract. We give necessary and sufficient conditions for a tuple of unbounded operators to be (jointly) subnormal. This criterion is then applied to characterize the subnormality of some special tuples of operators, in particular commuting bilateral weighted multi-shifts.
AMS Subject Classification
(1991): 47B20, 44A60, 47A20, 47B37
Received February 11, 2002, and in revised form May 10, 2002. (Registered under 2930/2009.)
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