<p>In this paper, we find sharp upper bounds for the higher-order Schwarzian functionals <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\sigma _n(f)(0)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>σ</mi> <mi>n</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>f</mi> <mo stretchy="false">)</mo> </mrow> <mrow> <mo stretchy="false">(</mo> <mn>0</mn> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, for <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(n=3,4\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>n</mi> <mo>=</mo> <mn>3</mn> <mo>,</mo> <mn>4</mn> </mrow> </math></EquationSource> </InlineEquation>, in two subclasses of univalent functions defined using the exponential function. These subclasses are the exponential starlike class <Equation ID="Equ19"> <EquationSource Format="TEX">\(\begin{aligned} \mathcal {S}_\textrm{e}^*=\left\{ f\in \mathcal {S}:\frac{zf'(z)}{f(z)}\prec \textrm{e}^z\right\} \end{aligned}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mtable> <mtr> <mtd columnalign="right"> <mrow> <msubsup> <mi mathvariant="script">S</mi> <mtext>e</mtext> <mo>∗</mo> </msubsup> <mo>=</mo> <mfenced close="}" open="{"> <mi>f</mi> <mo>∈</mo> <mi mathvariant="script">S</mi> <mo>:</mo> <mfrac> <mrow> <mi>z</mi> <msup> <mi>f</mi> <mo>′</mo> </msup> <mrow> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> </mrow> <mrow> <mi>f</mi> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> </mfrac> <mo>≺</mo> <msup> <mtext>e</mtext> <mi>z</mi> </msup> </mfenced> </mrow> </mtd> </mtr> </mtable> </mrow> </math></EquationSource> </Equation>and the exponential convex class <Equation ID="Equ20"> <EquationSource Format="TEX">\(\begin{aligned} \mathcal {C}_\textrm{e}=\left\{ f\in \mathcal {S}:1+\frac{zf''(z)}{f'(z)}\prec \textrm{e}^z\right\} . \end{aligned}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mtable> <mtr> <mtd columnalign="right"> <mrow> <msub> <mi mathvariant="script">C</mi> <mtext>e</mtext> </msub> <mo>=</mo> <mfenced close="}" open="{"> <mi>f</mi> <mo>∈</mo> <mi mathvariant="script">S</mi> <mo>:</mo> <mn>1</mn> <mo>+</mo> <mfrac> <mrow> <mi>z</mi> <msup> <mi>f</mi> <mrow> <mo>′</mo> <mo>′</mo> </mrow> </msup> <mrow> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> </mrow> <mrow> <msup> <mi>f</mi> <mo>′</mo> </msup> <mrow> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </mfrac> <mo>≺</mo> <msup> <mtext>e</mtext> <mi>z</mi> </msup> </mfenced> <mo>.</mo> </mrow> </mtd> </mtr> </mtable> </mrow> </math></EquationSource> </Equation>For functions in <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\mathcal {C}_\textrm{e}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="script">C</mi> <mtext>e</mtext> </msub> </math></EquationSource> </InlineEquation>, we prove that <Equation ID="Equ21"> <EquationSource Format="TEX">\(\begin{aligned} |\sigma _3(f)(0)|\le 1,\quad |\sigma _4(f)(0)|\le 2. \end{aligned}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mtable> <mtr> <mtd columnalign="right"> <mrow> <mrow> <mo stretchy="false">|</mo> </mrow> <msub> <mi>σ</mi> <mn>3</mn> </msub> <mrow> <mrow> <mo stretchy="false">(</mo> <mi>f</mi> <mo stretchy="false">)</mo> </mrow> <mrow> <mo stretchy="false">(</mo> <mn>0</mn> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">|</mo> <mo>≤</mo> <mn>1</mn> <mo>,</mo> <mspace width="1em" /> <mo stretchy="false">|</mo> </mrow> <msub> <mi>σ</mi> <mn>4</mn> </msub> <mrow> <mrow> <mo stretchy="false">(</mo> <mi>f</mi> <mo stretchy="false">)</mo> </mrow> <mrow> <mo stretchy="false">(</mo> <mn>0</mn> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">|</mo> <mo>≤</mo> <mn>2</mn> <mo>.</mo> </mrow> </mrow> </mtd> </mtr> </mtable> </mrow> </math></EquationSource> </Equation>For functions in <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\mathcal {S}_\textrm{e}^*\)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi mathvariant="script">S</mi> <mtext>e</mtext> <mo>∗</mo> </msubsup> </math></EquationSource> </InlineEquation>, we show that <Equation ID="Equ22"> <EquationSource Format="TEX">\(\begin{aligned} |\sigma _3(f)(0)|\le 3,\quad |\sigma _4(f)(0)|\le 16\sqrt{\tfrac{3}{11}}. \end{aligned}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mtable> <mtr> <mtd columnalign="right"> <mrow> <mrow> <mo stretchy="false">|</mo> </mrow> <msub> <mi>σ</mi> <mn>3</mn> </msub> <mrow> <mrow> <mo stretchy="false">(</mo> <mi>f</mi> <mo stretchy="false">)</mo> </mrow> <mrow> <mo stretchy="false">(</mo> <mn>0</mn> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">|</mo> <mo>≤</mo> <mn>3</mn> <mo>,</mo> <mspace width="1em" /> <mo stretchy="false">|</mo> </mrow> <msub> <mi>σ</mi> <mn>4</mn> </msub> <mrow> <mrow> <mo stretchy="false">(</mo> <mi>f</mi> <mo stretchy="false">)</mo> </mrow> <mrow> <mo stretchy="false">(</mo> <mn>0</mn> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">|</mo> <mo>≤</mo> <mn>16</mn> </mrow> <msqrt> <mstyle displaystyle="false" scriptlevel="0"> <mfrac> <mn>3</mn> <mn>11</mn> </mfrac> </mstyle> </msqrt> <mo>.</mo> </mrow> </mtd> </mtr> </mtable> </mrow> </math></EquationSource> </Equation>As application, the sharp Schwarzian bounds induce corresponding sharp estimates for the initial Grunsky coefficients <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(b_{n,m}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>b</mi> <mrow> <mi>n</mi> <mo>,</mo> <mi>m</mi> </mrow> </msub> </math></EquationSource> </InlineEquation>, for exponentially subordinate functions.</p>

错误:搜索内容不能为空,请输入英文关键词
错误:关键词超出字数限制,请精简
高级检索

Sharp estimates of Schippers higher-order Schwarzian derivatives for various classes

  • Pradip Das

摘要

In this paper, we find sharp upper bounds for the higher-order Schwarzian functionals \(\sigma _n(f)(0)\) σ n ( f ) ( 0 ) , for \(n=3,4\) n = 3 , 4 , in two subclasses of univalent functions defined using the exponential function. These subclasses are the exponential starlike class \(\begin{aligned} \mathcal {S}_\textrm{e}^*=\left\{ f\in \mathcal {S}:\frac{zf'(z)}{f(z)}\prec \textrm{e}^z\right\} \end{aligned}\) S e = f S : z f ( z ) f ( z ) e z and the exponential convex class \(\begin{aligned} \mathcal {C}_\textrm{e}=\left\{ f\in \mathcal {S}:1+\frac{zf''(z)}{f'(z)}\prec \textrm{e}^z\right\} . \end{aligned}\) C e = f S : 1 + z f ( z ) f ( z ) e z . For functions in \(\mathcal {C}_\textrm{e}\) C e , we prove that \(\begin{aligned} |\sigma _3(f)(0)|\le 1,\quad |\sigma _4(f)(0)|\le 2. \end{aligned}\) | σ 3 ( f ) ( 0 ) | 1 , | σ 4 ( f ) ( 0 ) | 2 . For functions in \(\mathcal {S}_\textrm{e}^*\) S e , we show that \(\begin{aligned} |\sigma _3(f)(0)|\le 3,\quad |\sigma _4(f)(0)|\le 16\sqrt{\tfrac{3}{11}}. \end{aligned}\) | σ 3 ( f ) ( 0 ) | 3 , | σ 4 ( f ) ( 0 ) | 16 3 11 . As application, the sharp Schwarzian bounds induce corresponding sharp estimates for the initial Grunsky coefficients \(b_{n,m}\) b n , m , for exponentially subordinate functions.