<p>For the family of complex rational functions of the form <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12346_2025_1312_Article_IEq1.gif" Format="GIF" Height="33" Rendition="HTML" Resolution="72" Type="Linedraw" Width="166" /> </InlineMediaObject> <EquationSource Format="TEX">\(R_{n,a,c}(z) = z^n + \dfrac{a}{z^n}+c\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>R</mi> <mrow> <mi>n</mi> <mo>,</mo> <mi>a</mi> <mo>,</mo> <mi>c</mi> </mrow> </msub> <mrow> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <msup> <mi>z</mi> <mi>n</mi> </msup> <mo>+</mo> <mstyle displaystyle="true" scriptlevel="0"> <mfrac> <mi>a</mi> <msup> <mi>z</mi> <mi>n</mi> </msup> </mfrac> </mstyle> <mo>+</mo> <mi>c</mi> </mrow> </math></EquationSource> </InlineEquation>, known as “Generalized McMullen maps”, for <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12346_2025_1312_Article_IEq2.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="40" /> </InlineMediaObject> <EquationSource Format="TEX">\(a\ne 0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>a</mi> <mo>≠</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12346_2025_1312_Article_IEq3.gif" Format="GIF" Height="15" Rendition="HTML" Resolution="72" Type="Linedraw" Width="43" /> </InlineMediaObject> <EquationSource Format="TEX">\(n \ge 3\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>n</mi> <mo>≥</mo> <mn>3</mn> </mrow> </math></EquationSource> </InlineEquation> fixed, we study the boundedness locus in some one-dimensional slices of the (<i>a</i>,&#xa0;<i>c</i>)-parameter space, by fixing a parameter or imposing a relation. First, if we fix <i>c</i> with <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12346_2025_1312_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="50" /> </InlineMediaObject> <EquationSource Format="TEX">\(|c|\ge 6\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">|</mo> <mi>c</mi> <mo stretchy="false">|</mo> <mo>≥</mo> <mn>6</mn> </mrow> </math></EquationSource> </InlineEquation> while allowing <i>a</i> to vary, assuming a modest lower bound on <i>n</i> in terms of |<i>c</i>|, we establish the location in the <i>a</i>-plane of <i>n</i> “baby" Mandelbrot sets, that is, homeomorphic copies of the original Mandelbrot set. We use polynomial-like maps, introduced by Douady and Hubbard ([<CitationRef CitationID="CR9">9</CitationRef>]) and applied for the subfamily <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12346_2025_1312_Article_IEq5.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="40" /> </InlineMediaObject> <EquationSource Format="TEX">\(R_{n,a,0}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>R</mi> <mrow> <mi>n</mi> <mo>,</mo> <mi>a</mi> <mo>,</mo> <mn>0</mn> </mrow> </msub> </math></EquationSource> </InlineEquation> by Devaney ([<CitationRef CitationID="CR4">4</CitationRef>]). Second, for slices in which <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12346_2025_1312_Article_IEq6.gif" Format="GIF" Height="13" Rendition="HTML" Resolution="72" Type="Linedraw" Width="48" /> </InlineMediaObject> <EquationSource Format="TEX">\(c=ta\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>c</mi> <mo>=</mo> <mi>t</mi> <mi>a</mi> </mrow> </math></EquationSource> </InlineEquation>, we again observe what look like baby Mandelbrot sets within these slices, and begin the study of this subfamily by establishing a neighborhood containing the boundedness locus.</p>

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Baby Mandelbrot Sets and Spines in Some One-Dimensional Subspaces of the Parameter Space for Generalized McMullen Maps

  • Suzanne Boyd,
  • Matthew Hoeppner

摘要

For the family of complex rational functions of the form \(R_{n,a,c}(z) = z^n + \dfrac{a}{z^n}+c\) R n , a , c ( z ) = z n + a z n + c , known as “Generalized McMullen maps”, for \(a\ne 0\) a 0 and \(n \ge 3\) n 3 fixed, we study the boundedness locus in some one-dimensional slices of the (ac)-parameter space, by fixing a parameter or imposing a relation. First, if we fix c with \(|c|\ge 6\) | c | 6 while allowing a to vary, assuming a modest lower bound on n in terms of |c|, we establish the location in the a-plane of n “baby" Mandelbrot sets, that is, homeomorphic copies of the original Mandelbrot set. We use polynomial-like maps, introduced by Douady and Hubbard ([9]) and applied for the subfamily \(R_{n,a,0}\) R n , a , 0 by Devaney ([4]). Second, for slices in which \(c=ta\) c = t a , we again observe what look like baby Mandelbrot sets within these slices, and begin the study of this subfamily by establishing a neighborhood containing the boundedness locus.