A completely monotonic function involving the gamma and tri-gamma functions

Feng Qi

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arXiv · 1307.5407

A completely monotonic function involving the gamma and tri-gamma functions

Feng Qi

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Abstract

In the paper the author provides necessary and sufficient conditions on $a$ for the function $\frac{1}{2}\ln(2\pi)-x+\bigl(x-\frac{1}{2}\bigr)\ln x-\ln\Gamma(x)+\frac1{12}{\psi'(x+a)}$ and its negative to be completely monotonic on $(0,\infty)$, where $a\ge0$ is a real number, $\Gamma(x)$ is the classical gamma function, and $\psi(x)=\frac{\Gamma'(x)}{\Gamma(x)}$ is the di-gamma function. As applications, some known results and new inequalities are derived.

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BibTeX RIS

Feng Qi. 2013-07-20. A completely monotonic function involving the gamma and tri-gamma functions. https://arxiv.org/abs/1307.5407

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