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Cartesian form of Putnam’s inequality for doubly commuting hyponormal $$n$$-tuples. (English) Zbl 0982.47021
The authors give some Cartesian form of Putnam’s inequality bounded by the area of the joint approximate point spectra for doubly commuting hyponormal $$n$$-tuples by using the inequality bounded by the area of the Xia spectra for semi-hyponormal $$n$$-tuples of operators given by Xia and give also some relation between the Taylor and Xia spectra of such $$n$$-tuples.

##### MSC:
 47B20 Subnormal operators, hyponormal operators, etc. 47A13 Several-variable operator theory (spectral, Fredholm, etc.)
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