Abstract
In this paper, we considered the generalized numerical radius of a bounded linear operator defined from a Hilbert space H into itself and derived certain basic properties of generalized numerical radius of normal and hyponormal operators. We then concentrate on nilpotent operators and operators that are involutions and idempotents and present estimates for the generalized numerical radius. We also considered several examples to illustrate our results.
Similar content being viewed by others
Data availability
Data sharing not applicable to this article as no datasets were generated or analysed during the current study.
References
Abu-Omar, A., Kittaneh, F.: A generalization of the numerical radius. Linear Algebra Appl. 428(7), 1460–1475 (2008)
Bottazzi, T., Conde, C.: Generalized numerical radius and related inequalities. Oper. Matrices 15(4), 1289–1308 (2021)
Bhunia, P., Dragomir, S.S., Moslehian, M.S., Paul, K.: Lectures on Numerical Radius Inequalities. Infosys Science Foundation Series in Mathematical Sciences. Springer, Cham (2022). ISBN:978-3-031-13669-6; 978-3-031-13670-2
Bhunia, P., Feki, K., Paul, K.: Generalized A-numerical radius of operators and related inequalities. Bull. Iran. Math. Soc. 48, 3883–3907 (2022)
Douglas, R.G.: Banach Algebra Techniques in Operator Theory. Academic Press, New York (1972)
Douglas, R.G.: On majorization, factorization, and range inclusion of operators on Hilbert space. Proc. Am. Math. Soc. 17(2), 413–415 (1966)
Dragomir, S.S.: The hypo-Euclidean norm of an n-tuple of vectors in inner product spaces and applications. J. Inequal. Pure Appl. Math. 8(2), 52 (2007)
Fujii, M., Furuta, T., Kamei, E.: Furuta’s inequality and its application to Ando’s theorem. Linear Algebra Appl. 179, 161–169 (1993)
Furuta, T.: Applications of order preserving operator inequalities. In: Operator Theory and Complex Analysis (Sapporo, 1991). Operator Theory: Advances and Applications, vol. 59, pp. 180–190. Birkhäuser, Basel (1992)
Gustafson, K.E., Rao, D.K.M.: Numerical Range. The Field of Values of Linear Operators and Matrices. Universitext, Springer, New York (1997)
Halmos, P.R.: A Hilbert Space Problem Book. Van Nostrand, Princeton (1967)
Kittaneh, F.: Notes on some inequalities for Hilbert space operators. Publ. Res. Inst. Math. Sci. 24(2), 283–293 (1988)
Mortad, M.H.: An application of the Putnam–Fuglede theorem to normal products of self-adjoint operators. Proc. Am. Math. Soc. 131, 3135–3141 (2003)
Mortad, M.H.: Counterexamples in Operator Theory. Birkhäuser/Springer, Cham (2022). ISBN:978-3-030-97813-6; 978-3-030-97814-3
Moslehian, M.S., Nazafi, H.: An extension of the Löwner–Heinz inequality. Linear Algebra Appl. 437(9), 2359–2365 (2012)
Tanahashi, K.: On log-hyponormal operators. Integral Equ. Oper. Theory 34(3), 364–372 (1999)
Uchiyama, M.: Operators which have commutative polar decomposition. In: Contributions to Operator Theory and its Applications: The Tsuyoshi Ando Anniversary Volume, pp. 197–208 (1993)
Yamazaki, T.: On upper and lower bounds of the numerical radius and an equality condition. Stud. Math. 178, 83–89 (2007)
Zamani, A., Moslehian, M.S., Xu, Q., Fu, C.: Numerical radius inequalities concerning with algebra norms. Mediterr. J. Math. 18(2), 1–13 (2021)
Zamani, A., Wojcik, P.: Another generalization of the numerical radius for Hilbert space operators. Linear Algebra Appl. 609, 114–128 (2021)
Zhang, F.: On the Bohr inequality of operators. J. Math. Anal. Appl. 333, 1264–1271 (2007)
Zhu, K.: Operator Theory in Function Spaces. Marcel Dekker, Inc., New York (1990)
Acknowledgements
The authors thank the referee and the editor for the valuable suggestions and comments on an earlier version. Incorporating appropriate responses to these in the article has led to a better presentation of the results.
Author information
Authors and Affiliations
Corresponding author
Additional information
Communicated by Yiu-Tung Poon.
Rights and permissions
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
About this article
Cite this article
Das, N., Jena, M.R. Generalized numerical radius of a bounded linear operator. Adv. Oper. Theory 8, 62 (2023). https://doi.org/10.1007/s43036-023-00289-3
Received:
Accepted:
Published:
DOI: https://doi.org/10.1007/s43036-023-00289-3