1,459 research outputs found

    Note on a Class of Completely Monotonic Functions Involving the Polygamma Functions

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    Some bounds for the complete elliptic integrals of the first and second kinds

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    In the article, the complete elliptic integrals of the first and second kinds are bounded by using the power series expansions of some functions, the celebrated Wallis' inequality, and an integral inequality due to R. P. Agarwal, P. Cerone, S. S. Dragomir and F. Qi.Comment: 9 page

    A class of completely monotonic functions involving divided differences of the psi and polygamma functions and some applications

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    A class of functions involving the divided differences of the psi function and the polygamma functions and originating from Kershaw's double inequality are proved to be completely monotonic. As applications of these results, the monotonicity and convexity of a function involving ratio of two gamma functions and originating from establishment of the best upper and lower bounds in Kershaw's double inequality are derived, two sharp double inequalities involving ratios of double factorials are recovered, the probability integral or error function is estimated, a double inequality for ratio of the volumes of the unit balls in Rnβˆ’1\mathbb{R}^{n-1} and Rn\mathbb{R}^n respectively is deduced, and a symmetrical upper and lower bounds for the gamma function in terms of the psi function is generalized.Comment: 11 page

    An alternative proof of Elezovi\'c-Giordano-Pe\v{c}ari\'c's theorem

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    In the present note, an alternative proof is supplied for Theorem~1 in [N. Elezovi\'c, C. Giordano and J. Pe\v{c}ari\'c, \textit{The best bounds in Gautschi's inequality}, Math. Inequal. Appl. \textbf{3} (2000), 239\nobreakdash--252.].Comment: 5 page

    Some properties of extended remainder of Binet's first formula for logarithm of gamma function

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    In the paper, we extend Binet's first formula for the logarithm of the gamma function and investigate some properties, including inequalities, star-shaped and sub-additive properties and the complete monotonicity, of the extended remainder of Binet's first formula for the logarithm of the gamma function and related functions.Comment: 8 page

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

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    The psi function ψ(x)\psi(x) is defined by ψ(x)=Ξ“β€²(x)Ξ“(x)\psi(x)=\frac{\Gamma'(x)}{\Gamma(x)} and ψ(i)(x)\psi^{(i)}(x) for i∈Ni\in\mathbb{N} denote the polygamma functions, where Ξ“(x)\Gamma(x) is the gamma function. In this paper we prove that a function involving the difference between [Οˆβ€²(x)]2+Οˆβ€²β€²(x)[\psi'(x)]^2+\psi''(x) and a proper fraction of xx is completely monotonic on (0,∞)(0,\infty).Comment: 10 page

    A refinement of a double inequality for the gamma function

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    In the paper, we present a monotonicity result of a function involving the gamma function and the logarithmic function, refine a double inequality for the gamma function, and improve some known results for bounding the gamma function.Comment: 8 page
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