Multiple orthogonal polynomials associated with an exponential cubic weight

We consider multiple orthogonal polynomials associated with the exponential cubic weight e−x3e−x3 over two contours in the complex plane. We study the basic properties of these polynomials, including the Rodrigues formula and nearest-neighbor recurrence relations. It turns out that the recurrence coefficients are related to a discrete Painlevé equation. The asymptotics of the recurrence coefficients, the ratio of the diagonal multiple orthogonal polynomials and the (scaled) zeros of these polynomials are also investigated.