<p>Let <i>f</i> be a locally univalent function defined on the unit disc <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\mathbb {U}\)</EquationSource> </InlineEquation>, and let <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\gamma _n \in [0,1]\)</EquationSource> </InlineEquation> and <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\omega _n \in \left[ 0, \frac{1}{2}\right] \)</EquationSource> </InlineEquation>. We consider the family of operators extending <i>f</i> to a holomorphic mapping from the unit ball <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\mathbb {B}\)</EquationSource> </InlineEquation> in <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(\mathbb {C}^n\)</EquationSource> </InlineEquation> to <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(\mathbb {C}^n\)</EquationSource> </InlineEquation> given by: <Equation ID="Equ1"> <EquationSource Format="TEX">\( \Theta _{n, \gamma _n, \omega _n}(f)(z)=\left( f\left( z_1\right) ,\left( \frac{f\left( z_1\right) }{z_1}\right) ^{\gamma _n}\left( f^{\prime }\left( z_1\right) \right) ^{\omega _n}z^{\prime }\right) \)</EquationSource> </Equation>where <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(z=\left( z_1, z^{\prime }\right) \in \mathbb {C}^n\)</EquationSource> </InlineEquation> and <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(z^{\prime }=\left( z_2, \ldots , z_n\right) \)</EquationSource> </InlineEquation>, <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(n\ge 2\)</EquationSource> </InlineEquation>. When <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(\omega _n=\frac{1}{2}\)</EquationSource> </InlineEquation> and <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(\gamma _n=0\)</EquationSource> </InlineEquation>, this operator coincides with the classical Roper-Suffridge extension operator. We first prove that the operator <InlineEquation ID="IEq12"> <EquationSource Format="TEX">\(\Theta _{n,\gamma _n,\omega _n}\)</EquationSource> </InlineEquation> maps the family of spirallike functions of type <InlineEquation ID="IEq13"> <EquationSource Format="TEX">\(\beta \)</EquationSource> </InlineEquation> (denoted by <InlineEquation ID="IEq14"> <EquationSource Format="TEX">\(\hat{S}_\beta \)</EquationSource> </InlineEquation>) into the class of mappings that have parametric representation on <InlineEquation ID="IEq15"> <EquationSource Format="TEX">\(\mathbb {B}^n\)</EquationSource> </InlineEquation> (denoted by <InlineEquation ID="IEq16"> <EquationSource Format="TEX">\(S^0 (\mathbb {B}^n)\)</EquationSource> </InlineEquation>). In the second part, we show that if <i>f</i> is a normalized univalent Bloch function on the unit disc <InlineEquation ID="IEq17"> <EquationSource Format="TEX">\(\mathbb {U}\)</EquationSource> </InlineEquation>, then <InlineEquation ID="IEq18"> <EquationSource Format="TEX">\(\Theta _{n,\gamma ,\omega }(f)\)</EquationSource> </InlineEquation> is a Bloch mapping on the unit ball <InlineEquation ID="IEq19"> <EquationSource Format="TEX">\(\mathbb {B}\)</EquationSource> </InlineEquation>.</p>

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Loewner chain associated with the generalized Graham-Kohr extension operator

  • Anamaria Paștiu

摘要

Let f be a locally univalent function defined on the unit disc \(\mathbb {U}\) , and let \(\gamma _n \in [0,1]\) and \(\omega _n \in \left[ 0, \frac{1}{2}\right] \) . We consider the family of operators extending f to a holomorphic mapping from the unit ball \(\mathbb {B}\) in \(\mathbb {C}^n\) to \(\mathbb {C}^n\) given by: \( \Theta _{n, \gamma _n, \omega _n}(f)(z)=\left( f\left( z_1\right) ,\left( \frac{f\left( z_1\right) }{z_1}\right) ^{\gamma _n}\left( f^{\prime }\left( z_1\right) \right) ^{\omega _n}z^{\prime }\right) \) where \(z=\left( z_1, z^{\prime }\right) \in \mathbb {C}^n\) and \(z^{\prime }=\left( z_2, \ldots , z_n\right) \) , \(n\ge 2\) . When \(\omega _n=\frac{1}{2}\) and \(\gamma _n=0\) , this operator coincides with the classical Roper-Suffridge extension operator. We first prove that the operator \(\Theta _{n,\gamma _n,\omega _n}\) maps the family of spirallike functions of type \(\beta \) (denoted by \(\hat{S}_\beta \) ) into the class of mappings that have parametric representation on \(\mathbb {B}^n\) (denoted by \(S^0 (\mathbb {B}^n)\) ). In the second part, we show that if f is a normalized univalent Bloch function on the unit disc \(\mathbb {U}\) , then \(\Theta _{n,\gamma ,\omega }(f)\) is a Bloch mapping on the unit ball \(\mathbb {B}\) .