Birth of a Cut in Unitary Random Matrix Ensembles
Department of Mathematics, Katholieke Universiteit Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium
Department of Mathematical Sciences, Brunel University West London, Uxbridge UB8 3PH UK
Correspondence: Correspondence to be sent to: tom.claeys{at}wis.kuleuven.be
We study unitary random matrix ensembles in the critical regime where a new cut arises away from the original spectrum. We perform a double scaling limit where the size of the matrices tends to infinity, but in such a way that only a bounded number of eigenvalues is expected in the newborn cut. It turns out that limits of the eigenvalue correlation kernel are given by Hermite kernels corresponding to a finite size Gaussian unitary ensemble (GUE). When modifying the double scaling limit slightly, we observe a remarkable transition each time the new cut picks up an additional eigenvalue, leading to a limiting kernel interpolating between GUE-kernels for matrices of size k and size k + 1. We prove our results using the Riemann–Hilbert approach.