<p>Let <i>p</i> be a normalized (monic and centered) quartic polynomial with non-trivial symmetry group. It is already known that if <i>p</i> is unicritical, with only two distinct zeros with the same multiplicity or having a root at the origin then the Julia set of its Chebyshev’s method <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(C_p\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>C</mi> <mi>p</mi> </msub> </math></EquationSource> </InlineEquation> is connected and symmetry groups of <i>p</i> and <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(C_p\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>C</mi> <mi>p</mi> </msub> </math></EquationSource> </InlineEquation> coincide&#xa0;(Nayak, T., Pal, S, Mediterr. J.Math. 22(1), 12 (2025)). Every other quartic polynomial is shown to be of the form <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(p_a (z)=(z^2 -1)(z^2-a)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>p</mi> <mi>a</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <mrow> <mo stretchy="false">(</mo> <msup> <mi>z</mi> <mn>2</mn> </msup> <mo>-</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> <mrow> <mo stretchy="false">(</mo> <msup> <mi>z</mi> <mn>2</mn> </msup> <mo>-</mo> <mi>a</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> where <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(a \in {\mathbb {C}}\setminus \{-1,0,1\}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>a</mi> <mo>∈</mo> <mi mathvariant="double-struck">C</mi> <mo lspace="0.15em" rspace="0.15em" stretchy="false">\</mo> <mo stretchy="false">{</mo> <mo>-</mo> <mn>1</mn> <mo>,</mo> <mn>0</mn> <mo>,</mo> <mn>1</mn> <mo stretchy="false">}</mo> </mrow> </math></EquationSource> </InlineEquation>. Some dynamical aspects of Chebyshev’s method <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(C_a\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>C</mi> <mi>a</mi> </msub> </math></EquationSource> </InlineEquation> of <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(p_a\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>p</mi> <mi>a</mi> </msub> </math></EquationSource> </InlineEquation> are investigated in this article for all real <i>a</i>. It is proved that all the extraneous fixed points of <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(C _a\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>C</mi> <mi>a</mi> </msub> </math></EquationSource> </InlineEquation> are repelling, which gives that there is no invariant Siegel disk for <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(C_a\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>C</mi> <mi>a</mi> </msub> </math></EquationSource> </InlineEquation>. It is also shown that there is no Herman ring in the Fatou set of <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(C_a\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>C</mi> <mi>a</mi> </msub> </math></EquationSource> </InlineEquation>. For positive <i>a</i>, it is proved that at least two immediate basins of <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(C_a\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>C</mi> <mi>a</mi> </msub> </math></EquationSource> </InlineEquation> corresponding to the zeros of <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(p_a\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>p</mi> <mi>a</mi> </msub> </math></EquationSource> </InlineEquation> are unbounded and simply connected. For negative <i>a</i>, it is however proved that all the four immediate basins of <InlineEquation ID="IEq12"> <EquationSource Format="TEX">\(C_a\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>C</mi> <mi>a</mi> </msub> </math></EquationSource> </InlineEquation> corresponding to the zeros of <InlineEquation ID="IEq13"> <EquationSource Format="TEX">\(p_a\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>p</mi> <mi>a</mi> </msub> </math></EquationSource> </InlineEquation> are unbounded and those corresponding to <InlineEquation ID="IEq14"> <EquationSource Format="TEX">\(\pm i\sqrt{|a|}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>±</mo> <mi>i</mi> <msqrt> <mrow> <mo stretchy="false">|</mo> <mi>a</mi> <mo stretchy="false">|</mo> </mrow> </msqrt> </mrow> </math></EquationSource> </InlineEquation> are simply connected.</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

On Dynamics of Chebyshev’s Method for Quartic Polynomials

  • Tarakanta Nayak,
  • Soumen Pal

摘要

Let p be a normalized (monic and centered) quartic polynomial with non-trivial symmetry group. It is already known that if p is unicritical, with only two distinct zeros with the same multiplicity or having a root at the origin then the Julia set of its Chebyshev’s method \(C_p\) C p is connected and symmetry groups of p and \(C_p\) C p coincide (Nayak, T., Pal, S, Mediterr. J.Math. 22(1), 12 (2025)). Every other quartic polynomial is shown to be of the form \(p_a (z)=(z^2 -1)(z^2-a)\) p a ( z ) = ( z 2 - 1 ) ( z 2 - a ) where \(a \in {\mathbb {C}}\setminus \{-1,0,1\}\) a C \ { - 1 , 0 , 1 } . Some dynamical aspects of Chebyshev’s method \(C_a\) C a of \(p_a\) p a are investigated in this article for all real a. It is proved that all the extraneous fixed points of \(C _a\) C a are repelling, which gives that there is no invariant Siegel disk for \(C_a\) C a . It is also shown that there is no Herman ring in the Fatou set of \(C_a\) C a . For positive a, it is proved that at least two immediate basins of \(C_a\) C a corresponding to the zeros of \(p_a\) p a are unbounded and simply connected. For negative a, it is however proved that all the four immediate basins of \(C_a\) C a corresponding to the zeros of \(p_a\) p a are unbounded and those corresponding to \(\pm i\sqrt{|a|}\) ± i | a | are simply connected.