Higher-Order Singularities without Glass-Glass Transitions

Within the framework of mode-coupling theory, the glass-transition scenario is investigated for a system of particles interacting with a hard-core repulsion and an additional square-shoulder soft core at larger distances. The static structure is calculated from the potential in Percus-Yevick approximation. For certain widths of the shoulder, the exponent parameter lambda along the glass-transition line shows a double peak. At both peaks, lambda can reach unity indicating the existence of higher-order glass-transition singularities. It is shown that these higher-order singularities originate from a line of avoided glass-glass transitions.