Schur products of operators and the essential numerical range
HTML articles powered by AMS MathViewer
- by Quentin F. Stout PDF
- Trans. Amer. Math. Soc. 264 (1981), 39-47 Request permission
Abstract:
Let $\mathcal {E} = \{ {e_n}\} _{n = 1}^\infty$ be an orthonormal basis for a Hilbert space $\mathcal {H}$. For operators $A$ and $B$ having matrices $({a_{ij}})_{i,\;j = 1}^\infty$ and $({b_{ij}})_{i,\;j}^\infty = 1$, their Schur product is defined to be $({a_{ij}}{b_{ij}})_{i,\:j}^\infty = 1$. This gives $\mathcal {B}(\mathcal {H})$ a new Banach algebra structure, denoted ${\mathcal {P}_\mathcal {E}}$. For any operator $T$ it is shown that $T$ is in the kernel (hull(compact operators)) in some ${\mathcal {B}_\mathcal {E}}$ iff $0$ is in the essential numerical range of $T$. These conditions are also equivalent to the property that there is a basis such that Schur multiplication by $T$ is a compact operator mapping Schatten classes into smaller Schatten classes. Thus we provide new results linking $\mathcal {B}(\mathcal {H})$, ${\mathcal {B}_\mathcal {E}}$ and $\mathcal {B}(\mathcal {B}(\mathcal {H}))$.References
-
J. Anderson, Derivations, commutators and the essential numerical range, Ph.D. Thesis, Indiana University, 1971.
- J. H. Anderson and J. G. Stampfli, Commutators and compressions, Israel J. Math. 10 (1971), 433–441. MR 312312, DOI 10.1007/BF02771730
- G. Bennett, Unconditional convergence and almost everywhere convergence, Z. Wahrscheinlichkeitstheorie und Verw. Gebiete 34 (1976), no. 2, 135–155. MR 407580, DOI 10.1007/BF00535681
- G. Bennett, Schur multipliers, Duke Math. J. 44 (1977), no. 3, 603–639. MR 493490
- F. F. Bonsall and J. Duncan, Numerical ranges of operators on normed spaces and of elements of normed algebras, London Mathematical Society Lecture Note Series, vol. 2, Cambridge University Press, London-New York, 1971. MR 0288583
- B. E. Johnson and J. P. Williams, The range of a normal derivation, Pacific J. Math. 58 (1975), no. 1, 105–122. MR 380490
- Shige Toshi Kuroda, On a theorem of Weyl-von Neumann, Proc. Japan Acad. 34 (1958), 11–15. MR 102751
- S. Kwapień and A. Pełczyński, The main triangle projection in matrix spaces and its applications, Studia Math. 34 (1970), 43–68. MR 270118, DOI 10.4064/sm-34-1-43-67
- Charles A. McCarthy, $c_{p}$, Israel J. Math. 5 (1967), 249–271. MR 225140, DOI 10.1007/BF02771613
- Albrecht Pietsch, $s$-numbers of operators in Banach spaces, Studia Math. 51 (1974), 201–223. MR 361883, DOI 10.4064/sm-51-3-201-223 C. Pommerenke, Univalent functions, Hubert, Göttingen, 1975.
- Heydar Radjavi and Peter Rosenthal, Matrices for operators and generators of $B({\cal H})$, J. London Math. Soc. (2) 2 (1970), 557–560. MR 265978, DOI 10.1112/jlms/2.Part_{3}.557
- William H. Ruckle, Hadamard multipliers of infinite matrices, Indiana Univ. Math. J. 24 (1974/75), 949–957. MR 370130, DOI 10.1512/iumj.1975.24.24079
- G. I. Russu, Intermediate symmetrically normed ideals, Funkcional. Anal. i Priložen. 3 (1969), no. 2, 94–95 (Russian). MR 0247492 L. Schur, Bemerkungen zur Theorie der beschrankten Bilinearformen mit unendlich vielen Veranderlichen, J. Reine Angew. Math. 140 (1911), 1-28. Q. F. Stout, Convex ideals of $\mathcal {B}(\mathcal {H})$ (to appear). —. Schur multiplication on $\mathcal {B}({l_p},\;{l_q})$ (to appear).
- George P. H. Styan, Hadamard products and multivariate statistical analysis, Linear Algebra Appl. 6 (1973), 217–240. MR 318177, DOI 10.1016/0024-3795(73)90023-2
- V. S. Sunder, Absolutely bounded matrices, Indiana Univ. Math. J. 27 (1978), no. 6, 919–927. MR 511247, DOI 10.1512/iumj.1978.27.27061
- N. Th. Varopoulos, A theorem on operator algebras, Math. Scand. 37 (1975), no. 1, 173–182. MR 397436, DOI 10.7146/math.scand.a-11599
- Dan Voiculescu, Some results on norm-ideal perturbations of Hilbert space operators, J. Operator Theory 2 (1979), no. 1, 3–37. MR 553861
Additional Information
- © Copyright 1981 American Mathematical Society
- Journal: Trans. Amer. Math. Soc. 264 (1981), 39-47
- MSC: Primary 47B37; Secondary 47A05, 47A10, 47D99
- DOI: https://doi.org/10.1090/S0002-9947-1981-0597865-2
- MathSciNet review: 597865