Jumping numbers of analytic multiplier ideals (with an appendix by Sebastien Boucksom)

We extend the study of jumping numbers of multiplier ideals due to Ein- Lazarsfeld-Smith-Varolin from the algebraic case to the case of general plurisubharmonic functions. While many properties established by Ein-Lazarsfeld-Smith-Varolin are shown to generalize to the plurisubharmonic case, important properties such as periodicity and discreteness do not hold any more. Previously only two particular examples with a cluster point (i.e. failure of discreteness) of jumping numbers were known, due to Guan-Li and to Ein-Lazarsfeld-Smith-Varolin. We generalize them to all toric plurisubharmonic functions in dimension 2 by characterizing precisely when cluster points of jumping numbers exist and by computing all those cluster points. This characterization suggests that clustering of jumping numbers is a rather frequent phenomenon. In particular, we obtain uncountably many new such examples.