We characterize the total positivity in space-time of strictly stable semigroups on R. In the positive case, this solves a problem that had been raised by Karlin.In the drifted Cauchy case, this concludes a study that we initiated in a previous paper. The case of the isotropic stable semigroup on R d is also investigated. We apply these results to the bell-shape and monotone likelihood properties of certain stable densities.
Let {X, X i , i = 1, 2, ...} denote independent positive random variables having common distribution function (d.f.) F(x) and, independent of X, let ν denote an integer valued random variable. Using X 0 = 0, the random sum Z = ν i=0
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