On mixtures of gamma distributions, distributions with hyperbolically monotone densities and generalized gamma convolutions (GGC)}
hyperbolically monotone densities and generalized
gamma convolutions (GGC)
Tord Sjödin
Abstract:
Let \(Y\) be a standard \({\rm Gamma}(k)\)
distributed random variable (rv), \(k>0\), and let \(X\)
be an independent positive rv. If \(X\) has a hyperbolically monotone density
of order \(k\) (\({\rm HM}_k\)),
then \(Y\cdot X\) and \(Y/X\)
are generalized gamma convolutions (GGC). This extends work by Roynette et al. and Behme and Bondesson.
The same conclusion holds with \(Y\) replaced by a finite sum of independent
gamma variables with sum of shape parameters at most \(k\).
Both results are applied to subclasses of GGC.
2010 AMS Mathematics Subject Classification: Primary 60E10; Secondary 62E15.
Keywords and phrases: gamma distribution, hyperbolically
monotone function, Laplace transform, generalized gamma convolution (GGC).