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On Toeplitz operators with piecewise continuous and slowly oscillating radial symbols. (English) Zbl 1333.47024

The paper is devoted to the study of Toeplitz operators with piecewise continuous and slowly oscillating radial symbols on the Bergman space \({\mathcal A}^2({\mathbb D})\). Let \(PC({\mathbb T})\) be the algebra of all piecewise continuous functions on the unit circle. By \(\mathrm{SO}([0,1))\) denote the algebra of all bounded continuous functions \(a\) on \([0,1)\) satisfying, for every \(\sigma\in(0,1)\), the following condition: \(\lim\limits_{\delta\to 0}\sup_{r,s\in[1-\delta,1-\sigma\delta]}|a(r)-a(s)|=0\). Let \(M_1(\mathrm{SO}[0,1))\) be the fiber of the maximal ideal space of \(\mathrm{SO}([0,1))\) consisting of all multiplicative linear functionals \(g\) such that \(g(a)=0\) whenever \(\lim\limits_{r\to 1}a(r)=0\). Let \({\mathcal K}\) denote the ideal of all compact operators on \({\mathcal A}^2({\mathbb D})\). The main result of the paper says that the Calkin algebra of the \(C^*\)-algebra generated by the Toeplitz operators with symbols in \(\mathrm{SO}([0,1))\otimes PC({\mathbb T})\) is isomorphic and isometric to the algebra of all continuous functions on the compact set \(M_1(\mathrm{SO}[0,1))\times ({\mathbb T}\times[0,1])\). The isomorphism is given by the following mapping of the generators \(T_{ab}+{\mathcal K}\mapsto\widehat{a}(\varphi)[b(t^-)(1-x)+b(t^+)x]\), where \(\varphi\in M_1(\mathrm{SO}([0,1)))\), \((t,x)\in{\mathbb T}\times[0,1]\), \(a\in \mathrm{SO}([0,1))\), \(b\in PC({\mathbb T})\), \(\widehat{a}\) is the Gelfand transform of the function \(a\), and the cylinder \([0,1]\times{\mathbb T}\) is equipped with a special topology first considered by I. Gohberg and N. Krupnik in the study of the algebra of Toeplitz operators with piecewise continuous symbols on the Hardy space \(H^2({\mathbb T})\) [I. Ts. Gokhberg and N. Ya. Krupnik, Funct. Anal. Appl. 3, 119–127 (1969; Zbl 0199.19201); translation from Funkts. Anal. Prilozh. 3, No. 2, 46–56 (1969)]. A local base of neighborhoods at the point \((t,x)\) consists of the sets \(\{t\}\times(x-\varepsilon,x+\varepsilon)\), \(0<\varepsilon<\min\{x,1-x\}\) if \(x\notin\{0,1\}\). For the point \((t,1)\), a local base of neighborhoods is \(([t,te^{i\varepsilon})\times(1-\varepsilon,1])\cup((t,te^{i\varepsilon})\times[0,1-\varepsilon])\) with \(0<\varepsilon<1\). Finally, for the point \((t,0)\), a local base of neighborhoods is \(((te^{-i\varepsilon},t]\times[0,\varepsilon))\cup((te^{-i\varepsilon},t)\times[\varepsilon,1])\) with \(0<\varepsilon<1\).

MSC:

47B35 Toeplitz operators, Hankel operators, Wiener-Hopf operators

Citations:

Zbl 0199.19201