Extremely non-complex spaces |
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Authors: | Piotr Koszmider Miguel Martín Javier Merí |
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Institution: | aInstytut Matematyki Politechniki Łódzkiej, ul. Wólczańska 215, 90-924 Łódź, Poland;bDepartamento de Análisis Matemático, Facultad de Ciencias, Universidad de Granada, 18071 Granada, Spain |
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Abstract: | We show that there exist infinite-dimensional extremely non-complex Banach spaces, i.e. spaces X such that the norm equality Id+T2 =1+ T2 holds for every bounded linear operator . This answers in the positive Question 4.11 of V. Kadets, M. Martín, J. Merí, Norm equalities for operators on Banach spaces, Indiana Univ. Math. J. 56 (2007) 2385–2411]. More concretely, we show that this is the case of some C(K) spaces with few operators constructed in P. Koszmider, Banach spaces of continuous functions with few operators, Math. Ann. 330 (2004) 151–183] and G. Plebanek, A construction of a Banach space C(K) with few operators, Topology Appl. 143 (2004) 217–239]. We also construct compact spaces K1 and K2 such that C(K1) and C(K2) are extremely non-complex, C(K1) contains a complemented copy of C(2ω) and C(K2) contains a (1-complemented) isometric copy of ℓ∞. |
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Keywords: | Banach space Few operators Complex structure Daugavet equation Space of continuous functions |
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