<p>Let <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(x \in [0,1)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>x</mi> <mo>∈</mo> <mo stretchy="false">[</mo> <mn>0</mn> <mo>,</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> be an irrational number with continued fraction expansion <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\([a_1(x),a_2(x), \cdots ,a_n(x),\cdots ]\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">[</mo> <msub> <mi>a</mi> <mn>1</mn> </msub> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> <mo>,</mo> <msub> <mi>a</mi> <mn>2</mn> </msub> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> <mo>,</mo> <mo>⋯</mo> <mo>,</mo> <msub> <mi>a</mi> <mi>n</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> <mo>,</mo> <mo>⋯</mo> <mo stretchy="false">]</mo> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(q_n(x)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>q</mi> <mi>n</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> be the denominator of its <i>n</i>-th convergent. We establish, for any <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\alpha ,\beta \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>α</mi> <mo>,</mo> <mi>β</mi> </mrow> </math></EquationSource> </InlineEquation> in <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\([0,+\infty ]\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">[</mo> <mn>0</mn> <mo>,</mo> <mo>+</mo> <mi>∞</mi> <mo stretchy="false">]</mo> </mrow> </math></EquationSource> </InlineEquation>, the Hausdorff dimension formula of the intersections of the sets of Dirichlet non-improvable numbers and the level set of convergent exponent, i.e. <Equation ID="Equ28"> <EquationSource Format="TEX">\( G(\alpha ,\beta ): =\left\{ x\in [0,1):\tau (x)=\alpha ,\,\,\text {and} \,\, \limsup _{n\rightarrow \infty }\frac{\log (a_n(x)a_{n+1}(x))}{\log q_n(x)}\ge \beta \right\} , \)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi>G</mi> <mrow> <mo stretchy="false">(</mo> <mi>α</mi> <mo>,</mo> <mi>β</mi> <mo stretchy="false">)</mo> </mrow> <mo>:</mo> <mo>=</mo> <mfenced close="}" open="{"> <mi>x</mi> <mo>∈</mo> <mrow> <mo stretchy="false">[</mo> <mn>0</mn> <mo>,</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> <mo>:</mo> <mi>τ</mi> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <mi>α</mi> <mo>,</mo> <mspace width="0.166667em" /> <mspace width="0.166667em" /> <mtext>and</mtext> <mspace width="0.166667em" /> <mspace width="0.166667em" /> <munder> <mo movablelimits="true">lim sup</mo> <mrow> <mi>n</mi> <mo stretchy="false">→</mo> <mi>∞</mi> </mrow> </munder> <mfrac> <mrow> <mo>log</mo> <mo stretchy="false">(</mo> <msub> <mi>a</mi> <mi>n</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> <msub> <mi>a</mi> <mrow> <mi>n</mi> <mo>+</mo> <mn>1</mn> </mrow> </msub> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">)</mo> </mrow> <mrow> <mo>log</mo> <msub> <mi>q</mi> <mi>n</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </mfrac> <mo>≥</mo> <mi>β</mi> </mfenced> <mo>,</mo> </mrow> </math></EquationSource> </Equation>and <Equation ID="Equ29"> <EquationSource Format="TEX">\( E(\alpha ,\beta ): =\left\{ x\in [0,1):\tau (x)=\alpha ,\,\,\text {and} \,\, \limsup _{n\rightarrow \infty }\frac{\log (a_n(x)a_{n+1}(x))}{\log q_n(x)}=\beta \right\} , \)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi>E</mi> <mrow> <mo stretchy="false">(</mo> <mi>α</mi> <mo>,</mo> <mi>β</mi> <mo stretchy="false">)</mo> </mrow> <mo>:</mo> <mo>=</mo> <mfenced close="}" open="{"> <mi>x</mi> <mo>∈</mo> <mrow> <mo stretchy="false">[</mo> <mn>0</mn> <mo>,</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> <mo>:</mo> <mi>τ</mi> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <mi>α</mi> <mo>,</mo> <mspace width="0.166667em" /> <mspace width="0.166667em" /> <mtext>and</mtext> <mspace width="0.166667em" /> <mspace width="0.166667em" /> <munder> <mo movablelimits="true">lim sup</mo> <mrow> <mi>n</mi> <mo stretchy="false">→</mo> <mi>∞</mi> </mrow> </munder> <mfrac> <mrow> <mo>log</mo> <mo stretchy="false">(</mo> <msub> <mi>a</mi> <mi>n</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> <msub> <mi>a</mi> <mrow> <mi>n</mi> <mo>+</mo> <mn>1</mn> </mrow> </msub> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">)</mo> </mrow> <mrow> <mo>log</mo> <msub> <mi>q</mi> <mi>n</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </mfrac> <mo>=</mo> <mi>β</mi> </mfenced> <mo>,</mo> </mrow> </math></EquationSource> </Equation>where <Equation ID="Equ30"> <EquationSource Format="TEX">\( \tau (x):= \inf \left\{ s \ge 0: \sum _{n \ge 1} a^{-s}_n(x)&lt;\infty \right\} . \)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi>τ</mi> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> <mo>:</mo> <mo>=</mo> <mo movablelimits="true">inf</mo> <mfenced close="}" open="{"> <mi>s</mi> <mo>≥</mo> <mn>0</mn> <mo>:</mo> <munder> <mo>∑</mo> <mrow> <mi>n</mi> <mo>≥</mo> <mn>1</mn> </mrow> </munder> <msubsup> <mi>a</mi> <mi>n</mi> <mrow> <mo>-</mo> <mi>s</mi> </mrow> </msubsup> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> <mo>&lt;</mo> <mi>∞</mi> </mfenced> <mo>.</mo> </mrow> </math></EquationSource> </Equation></p>

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Convergence exponent of Dirichlet non-improvable numbers in the theory of continued fractions

  • Xiaoyan Tan,
  • Zhenliang Zhang

摘要

Let \(x \in [0,1)\) x [ 0 , 1 ) be an irrational number with continued fraction expansion \([a_1(x),a_2(x), \cdots ,a_n(x),\cdots ]\) [ a 1 ( x ) , a 2 ( x ) , , a n ( x ) , ] and \(q_n(x)\) q n ( x ) be the denominator of its n-th convergent. We establish, for any \(\alpha ,\beta \) α , β in \([0,+\infty ]\) [ 0 , + ] , the Hausdorff dimension formula of the intersections of the sets of Dirichlet non-improvable numbers and the level set of convergent exponent, i.e. \( G(\alpha ,\beta ): =\left\{ x\in [0,1):\tau (x)=\alpha ,\,\,\text {and} \,\, \limsup _{n\rightarrow \infty }\frac{\log (a_n(x)a_{n+1}(x))}{\log q_n(x)}\ge \beta \right\} , \) G ( α , β ) : = x [ 0 , 1 ) : τ ( x ) = α , and lim sup n log ( a n ( x ) a n + 1 ( x ) ) log q n ( x ) β , and \( E(\alpha ,\beta ): =\left\{ x\in [0,1):\tau (x)=\alpha ,\,\,\text {and} \,\, \limsup _{n\rightarrow \infty }\frac{\log (a_n(x)a_{n+1}(x))}{\log q_n(x)}=\beta \right\} , \) E ( α , β ) : = x [ 0 , 1 ) : τ ( x ) = α , and lim sup n log ( a n ( x ) a n + 1 ( x ) ) log q n ( x ) = β , where \( \tau (x):= \inf \left\{ s \ge 0: \sum _{n \ge 1} a^{-s}_n(x)<\infty \right\} . \) τ ( x ) : = inf s 0 : n 1 a n - s ( x ) < .