Specific features of cosquares of special matrices in indefinite metric spaces
Zapiski Nauchnykh Seminarov POMI, Computational methods and algorithms. Part XXXIII, Tome 496 (2020), pp. 101-103
Kh. D. Ikramov. Specific features of cosquares of special matrices in indefinite metric spaces. Zapiski Nauchnykh Seminarov POMI, Computational methods and algorithms. Part XXXIII, Tome 496 (2020), pp. 101-103. http://geodesic.mathdoc.fr/item/ZNSL_2020_496_a7/
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     title = {Specific features of cosquares of special matrices in indefinite metric spaces},
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     url = {http://geodesic.mathdoc.fr/item/ZNSL_2020_496_a7/}
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Voir la notice du chapitre de livre provenant de la source Math-Net.Ru

As is known, the cosquare of an arbitrary nonsingular Hermitian matrix is the identity matrix, and the cosquare of an arbitrary unitary matrix is again unitary. In a complex linear space with the symplectic metric, symplectic and skew-Hamiltonian matrices are the counterparts of unitary and Hermitian matrices, respectively. Specific features of cosquares for these two matrix classes are indicated.

[1] R. A. Horn, C. R. Johnson, Matrix Analysis, Second edition, Cambridge University Press, Cambridge, 2013 | MR | Zbl