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On closure and factorization properties of subexponential and related distributions

Published online by Cambridge University Press:  09 April 2009

Paul Embrechts
Affiliation:
Department Wiskunde Katholieke Universiteit LeuvenCelestijnenlaan 200B, B-3030 Heverlee Belgium
Charles M. Goldie
Affiliation:
Department of Mathematics Westfield College University of LondonKidderpore Avenue London NW3 7ST, United Kingdom
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Abstract

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For a distribution function F on [0, ∞] we say Fif {1 – F(2)(x)}/{1 – F(x)}→2 as x→∞, and F, if for some fixed γ > 0, and for each real , limx→∞ {1 – F(x + y)}/{1 – F(x)} ═ e– n. Sufficient conditions are given for the statement FF * Gand when both F and G are in y it is proved that F*GpF + 1(1 – p) G ∈ for some (all) p ∈(0,1). The related classes ℒt are proved closed under convolutions, which implies the closure of the class of positive random variables with regularly varying tails under multiplication (of random variables). An example is given that shows to be a proper subclass of ℒ 0.

Type
Research Article
Copyright
Copyright © Australian Mathematical Society 1980

References

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