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Professor Emeritus, Department of Mathematical Sciences, Seoul National University
E-mail: wylee@snu.ac.kr
I am interested in exploring the interplay between function theory and operator theory, with a specific focus on the invariant subspace problem. The invariant subspace problem is a simple question: “Does every bounded linear operator on a separable complex Hilbert space have a nontrivial invariant subspace?” This problem was fundamentally addressed by J. von Neumann in 1934. The problem is easy to state, however, it is still unsolved. This fascination takes me on a journey encompassing various fields, such as functional analysis, operator theory, complex analysis, harmonic analysis and etc.
Publications (Selecta)
Almost invariant subspaces of shift operators and products of Toeplitz and Hankel operators (with C. Gu, I.S. Hwang, H. Kim and J. Park)
Journal of Operator Theory 95(1) (2026), 101-126. PDF
Subnormal block Toeplitz operators (with M. Abhinand, R. Curto, I.S. Hwang, and T. Prasad)
Journal d'Analyse Mathematique 155(2) (2025), 485-500 PDF
Circle companions of Hardy spaces of the unit disk (with R. Curto, I.S. Hwang, S. Kim)
Journal of Functional Analysis 285 (2023), Art. ID 110159. PDF
Higher-order de Branges-Rovnyak and sub-Bergman spaces (with C. Gu, I.S. Hwang, J. Park)
Advances in Mathematics 428 (2023), Art. ID 109143, 49 pp. PDF
Recent developments in the interplay between function theory and operator theory for block Toeplitz, Hankel, and model operators, Function Spaces, Theory and Applications (with R. Curto, I.S. Hwang)
Fields Institute Communications Vol. 87, 287-329, Springer, 2023 PDF
Operator-valued rational functions (with R. Curto, I.S. Hwang)
Journal of Functional Analysis 283(9) (2022), Art. ID 109640, 23pp. PDF
The Beurling-Lax-Halmos Theorem for infinite multiplicity (with R. Curto, I.S. Hwang)
Journal of Functional Analysis 280(6) (2021), Art. ID 108884, 101 pp. PDF
Matrix functions of bounded type: An interplay between function theory and operator theory (with R. Curto, I.S. Hwang)
Memoirs of the American Mathematical Society 260 (2019), No. 1253, x+100pp. PDF
An answer to a question of A. Lubin: The lifting problem for commuting subnormals (with S.H. Lee, J. Yoon)
Israel Journal of Mathematics 222 (2017), 201-222. PDF
Subnormal and quasinormal Toeplitz operators with matrix-valued rational symbols (with R. R. Curto, I.S. Hwang. D.-O. Kang)
Advances in Mathematics 255 (2014), 561-585.
Which subnormal Toeplitz operators are either normal or analytic? (with R. Curto, I.S. Hwang)
Journal of Functional Analysis 263(8) (2012), 2333-2354
Hyponormality and subnormality of block Toepltz operators (with R. Curto, I.S. Hwang)
Advances in Mathematics 230 (2012), 2094-2151
Hyponormality of Toeplitz operators with rational symbols (with I.S. Hwang)
Mathematische Annalen 335 (2006), 405-414
Hyponormal Toeplitz operators with rational symbols (with I.S. Hwang)
Journal of Operator Theory 56(1) (2006), 47–58.
k-hyponormality of finite perturbations of unilateral weighted shifts (with R. Curto)
Transactions of the American Mathematical Society 357(12) (2005), 4719-4737
Hyponormality of trigonometric Toeplitz operators (with I.S. Hwang)
Transactions of the American Mathematical Society 354 (2002), 2461-2474
Joint hyponormality of Toeplitz pairs (with R. Curto)
Memoirs of the American Mathematical Society 150 (2001), No. 712.
Hyponormality of Toeplitz operators with polynomial symbols: an extremal case (with I.S. Hwang, I.H. Kim)
Mathematische Nachrichten 231 (2001), 25-38
The spectrum is continuous on the set of p-hyponormal operators (with I.S. Hwang)
Mathematische Zeitschrift 235 (2000), 151-157
Hyponormality of Toeplitz operators with polynomial symbols (with I.S. Hwang, I.H. Kim)
Mathematische Annalen 313(2) (1999), 247-261
Another note on Weyl's theorem (with R.E. Harte)
Transactions of the American Mathematical Society 349(5) (1997), 2115-2124
Normal Toeplitz matrices (with D.R. Farenick, M. Krupnik, N. Krupnik)
SIAM Journal of Matrix Analysis and Applications 17(4) (1996), 1037-1043
Hyponormality and spectra of Toeplitz operators (with D.R. Farenick)
Transactions of the American Mathematical Society 348(10) (1996), 4153-4174
Lecture Notes
Miscellany
Chair of Department of Mathematical Sciences, Seoul Nat’l Univ. (Jan 2008 - Dec 2009)
Director of SRC (PARC) at Seoul Nat’l Univ. (Sep 2009 - Aug 2016)
Fellow of KAST (Korean Academy of Sciences and Technology) (Jan 2013 – present)
Director of Research Institute of Mathematics, Seoul Nat’l Univ. (Jan 2018 - Feb 2021)
Chair of Division of Natural Sciences, KAST (Jan 2019 – Dec 2021)
Editor in Chief of the Journal of the Korean Mathematical Society (2001 - 2002, 2005 - 2006, 2008 - 2010)
HCMC Distinguished Professor, KIAS (2023.08~2026.02)
Awards
Academic Achievement (Haksul) Awards, Korean Mathematical Society, 2001
SNU Awards, Seoul Nat’l Univ., 2017
DI Awards, Korean Mathematical Society, 2019
Lifetime Achievement Awards, College of Natural Sciences, Seoul Nat’l Univ., 2021
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