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arXiv · 1209.3350

Sharp two parameter bounds for logarithmic and arithmetic-geometric means

Yu-Ming Chu·Ye-Fang Qiu·Miao-Kun Wang·Xiao-Yan Ma
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Abstract

For fixed $s\geq 1$ and $t_{1},t_{2}\in(0,1/2)$ we prove that the inequalities $G^{s}(t_{1}a+(1-t_{1})b,t_{1}b+(1-t_{1})a)A^{1-s}(a,b)>AG(a,b)$ and $G^{s}(t_{2}a+(1-t_{2})b,t_{2}b+(1-t_{2})a)A^{1-s}(a,b)>L(a,b)$ hold for all $a,b>0$ with $a\neq b$ if and only if $t_{1}\geq 1/2-\sqrt{2s}/(4s)$ and $t_{2}\geq 1/2-\sqrt{6s}/(6s)$. Here $G(a,b)$, $L(a,b)$, $AG(a,b)$ and $A(a,b)$ are the geometric, logarithmic, arithmetic-geometric and arithmetic means of $a$ and $b$, respectively.

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Yu-Ming Chu, Ye-Fang Qiu, Miao-Kun Wang, Xiao-Yan Ma. 2012-09-15. Sharp two parameter bounds for logarithmic and arithmetic-geometric means. https://arxiv.org/abs/1209.3350

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