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I need a special inequality related to a fractional derivative problem. Let k∈ℕ ,0<α<1 , 0<β<1.Consider : A=[Γ(1-α)Γ(1+k-β)/Γ(2-β-α+k)].(1-α) On what conditions (on k ,β and α) A is less than 1. I do not know anything about this kind of questions. Thank's a lot.

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put on hold as off-topic by Stopple, Steven Sam, Stefan Kohl, Lucia, abx 9 hours ago

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Your function is the Beta function $B(1-\alpha,1+k-\beta)$. See any book on special functions, for example, Andrews-Askey-Roy. –  Stopple 13 hours ago

1 Answer 1

Stopple is right, $A=B(1-\alpha, 1+k-\beta)$, where $B$ is the Beta function. However it seems in your formulation that $\alpha,\beta$ are fixed and $k$ is running through $\mathbb N$. Then a simple application of Stirling's formula gives $$ B(1-\alpha, 1+k-\beta)\sim (1+k+\beta)^{\alpha-1}\Gamma(1-\alpha),\quad k\rightarrow +\infty. $$ In particular, it goes to zero when $k$ goes to infinity.

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