“…The sub-Gaussian property Kozachenko, 1980, 2000;Pisier, 2016) and related concentration inequalities (Boucheron et al, 2013;Raginsky and Sason, 2013) have attracted a lot of attention in the last couple of decades due to their applications in various areas such as pure mathematics, physics, information theory and computer sciences. Recent interest focused on deriving the optimal proxy variance for discrete random variables like the Bernoulli distribution (Buldygin and Moskvichova, 2013;Kearns and Saul, 1998;Berend and Kontorovich, 2013) and the missing mass (McAllester and Schapire, 2000;McAllester and Ortiz, 2003;Berend and Kontorovich, 2013;Ben-Hamou et al, 2017). Our focus is instead on two continuous random variables, the Beta and Dirichlet distributions, for which the optimal proxy variance was not known to the best of our knowledge.…”