<p>We introduce a new subclass of starlike functions defined as <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11253_2025_2434_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="390" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathcal{S}}_{\tau }^{\ast} := \left\{f\in \mathcal{A}:z{f}^{\prime}\left(z\right)/f\left(z\right)\prec 1+\text{arctan }z=:\tau \left(z\right)\right\},\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mi mathvariant="script">S</mi> <mrow> <mi>τ</mi> </mrow> <mo>*</mo> </msubsup> <mo>:</mo> <mo>=</mo> <mfenced close="}" open="{"> <mi>f</mi> <mo>∈</mo> <mi mathvariant="script">A</mi> <mo>:</mo> <mi>z</mi> <msup> <mrow> <mi>f</mi> </mrow> <mo>′</mo> </msup> <mfenced close=")" open="("> <mi>z</mi> </mfenced> <mo stretchy="false">/</mo> <mi>f</mi> <mfenced close=")" open="("> <mi>z</mi> </mfenced> <mo>≺</mo> <mn>1</mn> <mo>+</mo> <mtext>arctan</mtext> <mspace width="0.333333em" /> <mi>z</mi> <mo>=</mo> <mo>:</mo> <mi>τ</mi> <mfenced close=")" open="("> <mi>z</mi> </mfenced> </mfenced> <mo>,</mo> </mrow> </math></EquationSource> </InlineEquation> where <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11253_2025_2434_Article_IEq2.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="35" /> </InlineMediaObject> <EquationSource Format="TEX">\(\tau \left(z\right)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>τ</mi> <mfenced close=")" open="("> <mi>z</mi> </mfenced> </mrow> </math></EquationSource> </InlineEquation> maps the unit disk <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11253_2025_2434_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="163" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathbb{D}}:=\left\{z\in {\mathbb{C}}:\left|z\right|&lt;1\right\}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="double-struck">D</mi> <mo>:</mo> <mo>=</mo> <mfenced close="}" open="{"> <mi>z</mi> <mo>∈</mo> <mi mathvariant="double-struck">C</mi> <mo>:</mo> <mfenced close="|" open="|"> <mi>z</mi> </mfenced> <mo>&lt;</mo> <mn>1</mn> </mfenced> </mrow> </math></EquationSource> </InlineEquation> onto a strip domain. We deduce structural formulas, as well as the growth and distortion theorems for <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11253_2025_2434_Article_IEq4.gif" Format="GIF" Height="18" Rendition="HTML" Resolution="72" Type="Linedraw" Width="25" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathcal{S}}_{\tau }^{*}.\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mmultiscripts> <mi mathvariant="script">S</mi> <mrow> <mi>τ</mi> </mrow> <mrow> <mrow /> <mo>∗</mo> </mrow> </mmultiscripts> <mo>.</mo> </mrow> </math></EquationSource> </InlineEquation> In addition, inclusion relations are established with some well-known subclasses of <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11253_2025_2434_Article_IEq5.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="15" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathcal{S}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="script">S</mi> </math></EquationSource> </InlineEquation> and sharp radius estimates are obtained, as well as the sharp coefficient bounds for the initial five coefficients and the second- and third-order Hankel determinants of <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11253_2025_2434_Article_IEq4.gif" Format="GIF" Height="18" Rendition="HTML" Resolution="72" Type="Linedraw" Width="25" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathcal{S}}_{\tau }^{*}.\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mmultiscripts> <mi mathvariant="script">S</mi> <mrow> <mi>τ</mi> </mrow> <mrow> <mrow /> <mo>∗</mo> </mrow> </mmultiscripts> <mo>.</mo> </mrow> </math></EquationSource> </InlineEquation></p>

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On a Subclass of Starlike Functions Associated with a Strip Domain

  • S. Sivaprasad Kumar,
  • Neha Verma

摘要

We introduce a new subclass of starlike functions defined as \({\mathcal{S}}_{\tau }^{\ast} := \left\{f\in \mathcal{A}:z{f}^{\prime}\left(z\right)/f\left(z\right)\prec 1+\text{arctan }z=:\tau \left(z\right)\right\},\) S τ * : = f A : z f z / f z 1 + arctan z = : τ z , where \(\tau \left(z\right)\) τ z maps the unit disk \({\mathbb{D}}:=\left\{z\in {\mathbb{C}}:\left|z\right|<1\right\}\) D : = z C : z < 1 onto a strip domain. We deduce structural formulas, as well as the growth and distortion theorems for \({\mathcal{S}}_{\tau }^{*}.\) S τ . In addition, inclusion relations are established with some well-known subclasses of \(\mathcal{S}\) S and sharp radius estimates are obtained, as well as the sharp coefficient bounds for the initial five coefficients and the second- and third-order Hankel determinants of \({\mathcal{S}}_{\tau }^{*}.\) S τ .