Definition of "coalescing"

We attribute such coalescings of eigenvalues to the presence of a finite barrier (on the either side of x=0 {\displaystyle {\text{x=0}}} ) which has been linked to a recent study of stokes phenomenon in the complex PT-symmetric potentials..

2015, Zafar Ahmed, Joseph Amal Nathan, Dhruv Sharma, Dona Ghosh, “Real discrete spectrum of complex PT-symmetric scattering potentials”, in arXiv‎