Kais Feki is an assistant Professor of Mathematics at the university of Monastir (Tunisia). Dr. Feki earned his M. Sc. from the University of Gabès (Tunisia) in 2016 and his Ph.D. from the University of Sfax (Tunisia) in 2019. His research focuses on functional analysis including multivariable operator theory and operator inequalities in Hilbert and semi-Hilbert spaces. In all his joint research papers, the authors names are placed according to alphabetical order. 

 

 

Kais Feki is a PhD in Mathematics. Dr. Feki earned his B.Sc. in Mathematics from the University of Sfax (Tunisia) in 2010, his M.Sc. in Mathematics from the University of Gabès (Tunisia) in 2016, and his Ph.D. in Mathematics from the University of Sfax  in 2019.

[1] H. Baklouti, K. Feki, O.A.M. Sid Ahmed, Joint numerical ranges of operators in semi-Hilbertian spaces,

Linear Algebra Appl. 555 266–284 (2018) 

 

[2] H. Baklouti, K. Feki, On joint spectral radius of commuting operators in Hilbert spaces, Linear Algebra

Appl. 557 455–463 (2018) 

 

[3] H. Baklouti, K. Feki, O.A.M. Sid Ahmed, Joint normality of operators in semi-Hilbertian spaces, Linear

Multilinear Algebra 68(4), 845–866 (2020) 

 

[4] H. Baklouti, K. Feki, Commuting tuples of normal operators in Hilbert spaces, Complex Anal. Oper.

Theory 14, 56 (2020) 

 

[5] K. Feki, Spectral radius of semi-Hilbertian space operators and its applications, Ann. Funct. Anal. 11,

929–946 (2020) 

 

[6] K. Feki, O.A.M. Sid Ahmed, Davis-Wielandt shells of semi-Hilbertian space operators and its applications,

Banach J. Math. Anal. 14, 1281–1304 (2020) 

 

[7] K. Feki, A note on doubly commuting tuples of hyponormal operators on Hilbert spaces, Results Math

75, 93 (2020) 

 

[8] K. Feki, A note on the A-numerical radius of operators in semi-Hilbert spaces, Arch. Math. 115, 535–544

(2020) 

 

[9] K. Feki, On tuples of commuting operators in positive semidefinite inner product spaces, Linear Algebra

Appl. 603, 313-328 (2020) 

 

[10] P. Bhunia, K. Feki, K. Paul, A-Numerical radius orthogonality and parallelism of semi-Hilbertian space

operators and their applications, Bull. Iran. Math. Soc. 47, 435–457 (2021) 

 

[11] K. Feki, Generalized numerical radius inequalities of operators in Hilbert spaces, Adv. Oper. Theory 6,

6 (2021) 

 

[12]  S. Chavan, K. Feki, Spherical symmetry of some unitary invariants for commuting tuples, Oper. Matrices

15 (3), 1131–1139 (2021) 

 

[13]  K. Feki, T. Yamazaki, Joint numerical radius of spherical Aluthge transforms of tuples of Hilbert space

operators, Math. Inequal. Appl. 24 (2), 405–420 (2021) 

 

[14]  K. Feki, Some bounds for the A-numerical radius of certain 2 × 2 operator matrices, Hacet. J. Math.

Stat. 50 (3), 795–810 (2021)

 

[15]  K. Feki, Some numerical radius inequalities for semi-Hilbert space operators, J. Korean Math. Soc., 58

(6), 1385–1405 (2021) 

 

[16] T. Bottazzi, C. Conde, K. Feki, On A-parallelism and A-Birkhoff-James orthogonality of operators,

Results Math 76, 209 (2021)

 

[17] K. Feki, F. Kittaneh, Some new refinements of generalized numerical radius inequalities for Hilbert space

operators, Mediterr. J. Math. 19, 17 (2022)

 

[18] K. Feki, Improved inequalities related to the A-numerical radius for commutators of operators, Turk J

Math, 46, 311–322, (2022) 

 

[19] K. Feki, Some A-numerical radius inequalities for d × d operator matrices, Rend. Circ. Mat. Palermo,

II. Ser 71, 85–103, (2022) 

 

[20] C. Conde, K. Feki, On some inequalities for the generalized joint numerical radius of semi-Hilbert space