Unified structures for solutions of Painlevé equation II

Abstract: We present certain general structures related to the solutions of Painlev\'e equation II and to the solutions of the differential equation satisfied by the corresponding Hamiltonian equations, together with the tau functions. By taking advantage of the B\"acklund transformations we find a linear differential equation satisfied by the tau functions and explicit rational expressions linking the solutions of Painlev\'e equation II, Painlev\'e equation XXXIV and the Hamiltonians with the tau functions. Also, recursions for the tau functions and the Hamiltonians will be given. Through the use of suitable parameters inserted into the equations, we consider a degenerate case solvable in terms of Weierstrass elliptic functions. The Yablonskii-Vorob'ev polynomials, the Airy-type solutions and the more general transcendental case are all described in separated Sections. Finally, certain integral relations are given.