<p>Consider the family of locally univalent analytic functions <i>h</i> in the unit disk <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40840_2025_1867_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="51" /> </InlineMediaObject> <EquationSource Format="TEX">\(|z|&lt;1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">|</mo> <mi>z</mi> <mo stretchy="false">|</mo> <mo>&lt;</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation> with the normalization <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40840_2025_1867_Article_IEq2.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="61" /> </InlineMediaObject> <EquationSource Format="TEX">\(h(0)=0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>h</mi> <mo stretchy="false">(</mo> <mn>0</mn> <mo stretchy="false">)</mo> <mo>=</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40840_2025_1867_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="65" /> </InlineMediaObject> <EquationSource Format="TEX">\(h'(0)=1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>h</mi> <mo>′</mo> </msup> <mrow> <mo stretchy="false">(</mo> <mn>0</mn> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation> and satisfying the condition <Equation ID="Equ13"> <MediaObject> <ImageObject Color="BlackWhite" FileRef="40840_2025_1867_Article_Equ13.gif" Format="GIF" Height="43" Rendition="HTML" Resolution="72" Type="Linedraw" Width="214" /> </MediaObject> <EquationSource Format="TEX">\({{\operatorname {Re}\,}} \left( \frac{z h''(z)}{\alpha h'(z)}\right) &lt;\frac{1}{2} ~ \text{ for } z\in {\mathbb D}\text{, } \)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mrow> <mo>Re</mo> <mspace width="0.166667em" /> </mrow> <mfenced close=")" open="("> <mfrac> <mrow> <mi>z</mi> <msup> <mi>h</mi> <mrow> <mo>′</mo> <mo>′</mo> </mrow> </msup> <mrow> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> </mrow> <mrow> <mi>α</mi> <msup> <mi>h</mi> <mo>′</mo> </msup> <mrow> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </mfrac> </mfenced> <mo>&lt;</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mspace width="3.33333pt" /> <mspace width="0.333333em" /> <mtext>for</mtext> <mspace width="0.333333em" /> <mi>z</mi> <mo>∈</mo> <mi mathvariant="double-struck">D</mi> <mtext>,</mtext> <mspace width="0.333333em" /> </mrow> </math></EquationSource> </Equation>where <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40840_2025_1867_Article_IEq4.gif" Format="GIF" Height="15" Rendition="HTML" Resolution="72" Type="Linedraw" Width="74" /> </InlineMediaObject> <EquationSource Format="TEX">\(0&lt;\alpha \le 1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>0</mn> <mo>&lt;</mo> <mi>α</mi> <mo>≤</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation>. The aim of this article is to show that this family has several elegant properties such as involving Blaschke products, Schwarzian derivative and univalent harmonic mappings.</p>

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Geometric Subfamily of Functions Convex in Some Direction and Blaschke Products

  • Liulan Li,
  • Saminthan Ponnusamy

摘要

Consider the family of locally univalent analytic functions h in the unit disk \(|z|<1\) | z | < 1 with the normalization \(h(0)=0\) h ( 0 ) = 0 , \(h'(0)=1\) h ( 0 ) = 1 and satisfying the condition \({{\operatorname {Re}\,}} \left( \frac{z h''(z)}{\alpha h'(z)}\right) <\frac{1}{2} ~ \text{ for } z\in {\mathbb D}\text{, } \) Re z h ( z ) α h ( z ) < 1 2 for z D , where \(0<\alpha \le 1\) 0 < α 1 . The aim of this article is to show that this family has several elegant properties such as involving Blaschke products, Schwarzian derivative and univalent harmonic mappings.