A superadditive property of Hadamard’s gamma function


DOI: 10.1007/s12188-008-0009-5

Cite this article as:
Alzer, H. Abh. Math. Semin. Univ. Hambg. (2009) 79: 11. doi:10.1007/s12188-008-0009-5


Hadamard’s gamma function is defined by
$$H(x)=\frac{1}{\Gamma(1-x)}\frac{d}{dx}\log \frac{\Gamma(1/2-x/2)}{\Gamma(1-x/2)},$$
where Γ denotes the classical gamma function of Euler. H is an entire function, which satisfies H(n)=(n−1)! for all positive integers n. We prove the following superadditive property.
Let α be a real number. The inequality
$$H(x)+H(y)\leq H(x+y)$$
holds for all real numbers x,y with x,yα if and only if αα0=1.5031…. Here, α0 is the only solution of H(2t)=2H(t) in [1.5,∞).


Hadamard’s and Euler’s gamma functionsPsi functionSuperadditiveConvexInequalities

Mathematics Subject Classification (2000)


Copyright information

© Mathematisches Seminar der Universität Hamburg and Springer 2008

Authors and Affiliations

  1. 1.WaldbrölGermany