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Indefinite higher-rank numerical ranges |
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| Authors: | N. Bebiano J. da Providência |
| Affiliation: | 1. Mathematics Department, University of Coimbra , P 3001-454, Coimbra , Portugal;2. Mathematics Department, CMUC , Coimbra , Portugal bebiano@mat.uc.pt;4. Physics Department , University of Coimbra , P 3004-516, Coimbra , Portugal |
| Abstract: | We investigate indefinite higher-rank numerical ranges of a wide class of J-Hermitian matrices, J?=?I r ?⊕??I n?r , 0?r?n (A?∈?C n×n is said to be J-Hermitian if A?=?JA*J). Particular attention is paid to aspects of the theory that parallel the case of Hermitian matrices. |
| Keywords: | indefinite inner product indefinite higher-rank numerical range classical numerical range J-Hermitian matrix J-normal matrix |