Anomalous monopoles of an interacting boson system

Two anomalous monopoles, one of line shape and the other of disk shape, are found to exist in the semiclassical theory of a two-mode interacting boson system. This is in stark contrast with the quantum theory of this system, where only point-like monopoles exist. We show that these two anomalous monopoles have different origins. The line-shaped monopole is formed from the merging of a series of point-like monopoles while the disk-shaped monopole is the result of the collapsing or bundling of field lines of Berry curvature due to the existence of the influence of the interaction between bosons. The relation of these two anomalous monopoles with the famed von Neumann-Wigner theorem is discussed.