On quasi-infinitely divisible random measures

Abstract: Quasi-infinitely divisible (QID) distributions have been recently introduced by Lindner, Pan and Sato (\textit{Trans.~Amer.~Math.~Soc.}~\textbf{370}, 8483-8520 (2018)). A random variable $X$ is QID if and only if there exist two infinitely divisible (ID) random variables $Y$ and $Z$ s.t.~$X+Y\stackrel{d}{=}Z$ and $Y$ is independent of $X$. In this work, we show that a family of QID completely random measures (CRMs) is dense in the space of all CRMs with respect to convergence in distribution. We further demonstrate that the elements of this family posses a L\'{e}vy-Khintchine formulation and that there exists a one to one correspondence between their law and certain characteristic pairs. We prove the same results also for the class of point processes with independent increments. In the second part of the paper, we show the relevance of these results in the general Bayesian nonparametric framework based on CRMs developed by Broderick, Wilson and Jordan (\textit{Bernoulli}, \textbf{24}, 3181-3221 (2018)).