Algebraic relations between solutions of Painlevé equations

In this manuscript, we make major progress classifying algebraic relations between solutions of Painlevé equations. Our main contribution is to establish the algebraic independence of solutions of various pairs of equations in the Painlevé families; for generic coefficients, we show that all algebraic relations between solutions of equations in the same Painlevé family come from classically studied Bäcklund transformations. We also apply our analysis of ranks to establish some transcendence results for pairs of Painlevé equations from different families. In that area, we answer several open questions of Nagloo, and in the process answer a question of Boalch. We calculate model-theoretic ranks of all Painlevé equations in this article, extending results of Nagloo and Pillay. We show that the type of the generic solution of any equation in the second Painlevé family is geometrically trivial, extending a result of Nagloo. We give the first model-theoretic analysis of several special families of the third Painlevé equation, proving results analogous to Nagloo and Pillay. We also give a novel new proof of the irreducibility of the third, fifth, and sixth Painlevé equations using recent work of Freitag, Jaoui, and Moosa. Our proof is fundamentally different from the existing transcendence proofs by Watanabe, Cantat and Loray, or Casale and Weil.