BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Lotte Hollands (Heriot-Watt University) DTSTART:20231219T193000Z DTEND:20231219T203000Z DTSTAMP:20260423T005731Z UID:nhetc/101 DESCRIPTION:Title: Non-perturbative partition functions for N=2 theories of class S\nby L otte Hollands (Heriot-Watt University) as part of NHETC Seminar\n\n\nAbstr act\nThe beautiful works by Gaiotto\, Moore and Neitzke have taught us (in particular) how to understand various kinds of BPS spectra for 4d N=2 the ories in terms of certain configurations of curves on a Riemann surface\, called spectral networks. In this talk I'll review how to generate a spect ral network for each point of the 4d Coulomb branch together with the choi ce of a phase. I'll point out that this data corresponds to a boundary con dition for the 4d N=2 theory in the half-Omega background\, and associate to it a new kind of N=2 partition function. This partition function is loc ally constant in the phase\, while its jumps are associated to 4d BPS part icles in the corresponding Coulomb vacuum. The well-known Nekrasov partiti on function (in the half-Omega background) may be recovered in a weakly co upled region of the Coulomb branch (if the theory admits any)\, at a speci al phase corresponding to a Fenchel-Nielsen spectral network. When lifted to five dimensions\, this new partition function becomes the non-perturbat ive topological string partition function.\n LOCATION:https://researchseminars.org/talk/nhetc/101/ END:VEVENT END:VCALENDAR