We present two examples. One of an operator T such that is precompact in the operator norm and the spectrum of T on the unit circle consists of an infinite number of points accumulating at 1, and the other of an operator T such that is convergent to zero but T is not power bounded.
@article{bwmeta1.element.bwnjournal-article-bcpv38i1p381bwm, author = {\'Swi\k ech, Andrzej}, title = {A note on the differences of the consecutive powers of operators}, journal = {Banach Center Publications}, volume = {38}, year = {1997}, pages = {381-383}, zbl = {0893.46039}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-bcpv38i1p381bwm} }
Święch, Andrzej. A note on the differences of the consecutive powers of operators. Banach Center Publications, Tome 38 (1997) pp. 381-383. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-bcpv38i1p381bwm/
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