Representations of quadratic Heisenberg-Weyl algebras and polynomials in the fourth Painlevé transcendent

Abstract: We provide new insights into the solvability property of an Hamiltonian involving of the fourth Painlev\'e transcendent and its derivatives. This Hamiltonian is third order shape invariant and can also be interpreted within the context of second supersymmetric quantum mechanics. In addition, this Hamiltonian admits third order lowering and raising operators. We will consider the case when this Hamiltonian is irreducible i.e. when no special solutions exist for given parameters $\alpha$ and $\beta$ of the fourth Painlev\'e transcendent $P_{IV}(x,\alpha,\beta)$. This means that the Hamiltonian does not admit a potential in terms of rational functions ( or hypergeometric type of special functions ) for those parameters. In such irreducible case, the ladder operators are involving the fourth Painlev\'e transcendent and its derivative. An important case for which this occurs is when the second parameter (i.e. $\beta$) of the fourth Painlev\'e transcendent $P_{IV}(x,\alpha,\beta)$ is strictly positive i.e. $\beta>0$. This Hamiltonian has been studied for all hierarchies of rational solutions that comes in three families connected to the generalised Hermite and Okamoto polynomials. The explicit form of ladder, the associated wavefunctions involving exceptional orthogonal polynomials and recurrence relations were also completed described. Here, we develop a description of the induced representations based on various commutator identities for highest and lowest weight type representations for the irreducible case. We also provide for such representations new formula concerning the explicit form of the related excited states from point of view of the Schrodinger equation as two variables polynomials that involve the fourth Painlev\'e transcendent and its derivative.