Abstract. Since the nineties, many 5d SCFT’s have been constructed by placing M-theory on noncompact, singular toric CY threefolds.
However, we know, since the results of Benini-Benvenuti-Tachikawa, that there are extra pieces of data in these setups that are only understood through the IIB 5-brane web paradigm, but have no known geometric counterpart.
In this talk, I will present the issue, and demonstrate how data from nilpotent orbits of the flavor group of the SCFT enter into the definition of such setups, and how Hanany-Witten moves uplift to M-theory.
The main point of this talk is to show how string theory captures physical information that is usually lost by looking at spectral data in the form of geometry.