Universality of global asymptotics of Jack-deformed random Young diagrams at varying temperatures


This paper establishes universal formulas describing the global asymptotics of two different models of discrete $\beta$-ensembles in high, low and fixed temperature regimes. Our results affirmatively answer a question posed by the second author and Śniady. We first consider the Jack measures on Young diagrams of arbitrary size, which depend on the inverse temperature parameter $\beta>0$ and specialize to Schur measures when $\beta=2$. We introduce a class of Jack measures of Plancherel-type and prove a law of large numbers and central limit theorem in the three regimes. In each regime, we provide explicit formulas for polynomial observables of the limit shape and Gaussian fluctuations around the limit shape. These formulas have surprising positivity properties and are expressed in terms of weighted lattice paths. We also establish connections between these measures and the work of Kerov-Okounkov-Olshanski on Jack-positive specializations and show that this is a rich class of measures parametrized by the elements in the Thoma cone. Second, we show that the formulas from limits of Plancherel-type Jack measures are universal: they also describe the limit shape and Gaussian fluctuations for the second model of random Young diagrams of a fixed size defined by Jack characters with the approximate factorization property (AFP) studied by the second author and Śniady. Finally, we discuss the limit shape in the high/low-temperature regimes and show that, contrary to the continuous case of $\beta$-ensembles, there is a phase transition phenomenon in passing from the fixed temperature regime to the high/low temperature regimes. We note that the relation we find between the two different models of random Young diagrams appears to be new, even in the special case of $\beta=2$ that relates Schur measures to the character measures with the AFP studied by Biane and Śniady.