<p>Let <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\lambda &gt;0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>λ</mi> <mo>&gt;</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\mathcal {K}_a\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="script">K</mi> <mi>a</mi> </msub> </math></EquationSource> </InlineEquation> denote the generalized elliptic integral of the first kind. Previous studies have confirmed the monotonicity and convexity of the function <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(x\mapsto \mathcal {K}_a(\sqrt{x})/\log (1+\lambda /\sqrt{1-x})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>x</mi> <mo>↦</mo> <msub> <mi mathvariant="script">K</mi> <mi>a</mi> </msub> <mrow> <mo stretchy="false">(</mo> <msqrt> <mi>x</mi> </msqrt> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">/</mo> <mo>log</mo> <mrow> <mo stretchy="false">(</mo> <mn>1</mn> <mo>+</mo> <mi>λ</mi> <mo stretchy="false">/</mo> <msqrt> <mrow> <mn>1</mn> <mo>-</mo> <mi>x</mi> </mrow> </msqrt> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> on the interval (0,&#xa0;1), where <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\log (1+\lambda /\sqrt{1-x})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>log</mo> <mo stretchy="false">(</mo> <mn>1</mn> <mo>+</mo> <mi>λ</mi> <mo stretchy="false">/</mo> <msqrt> <mrow> <mn>1</mn> <mo>-</mo> <mi>x</mi> </mrow> </msqrt> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> serves as a non-Ramanujan asymptotic function–distinct from the traditional Ramanujan asymptotic forms typically associated with such special functions–for the zero-balanced hypergeometric function. In this paper, these properties are extended to the zero-balanced hypergeometric function. Specifically, we establish the monotonicity and convexity of the function of <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="MediaObjects/40840_2026_2053_IEq5_HTML.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="120" Type="Linedraw" Width="307" /> </InlineMediaObject> </InlineEquation>, as well as the concavity of its reciprocal, all defined on (0,&#xa0;1). This result also provides a positive verification of a conjecture proposed by Yang and Tian when <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(a=b=1/2\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>a</mi> <mo>=</mo> <mi>b</mi> <mo>=</mo> <mn>1</mn> <mo stretchy="false">/</mo> <mn>2</mn> </mrow> </math></EquationSource> </InlineEquation>.</p>

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Non-Ramanujan Asymptotic Approximation for Zero-Balanced Hypergeometric Functions

  • Tiehong Zhao,
  • Miaokun Wang

摘要

Let \(\lambda >0\) λ > 0 and \(\mathcal {K}_a\) K a denote the generalized elliptic integral of the first kind. Previous studies have confirmed the monotonicity and convexity of the function \(x\mapsto \mathcal {K}_a(\sqrt{x})/\log (1+\lambda /\sqrt{1-x})\) x K a ( x ) / log ( 1 + λ / 1 - x ) on the interval (0, 1), where \(\log (1+\lambda /\sqrt{1-x})\) log ( 1 + λ / 1 - x ) serves as a non-Ramanujan asymptotic function–distinct from the traditional Ramanujan asymptotic forms typically associated with such special functions–for the zero-balanced hypergeometric function. In this paper, these properties are extended to the zero-balanced hypergeometric function. Specifically, we establish the monotonicity and convexity of the function of , as well as the concavity of its reciprocal, all defined on (0, 1). This result also provides a positive verification of a conjecture proposed by Yang and Tian when \(a=b=1/2\) a = b = 1 / 2 .