BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Okke van Garderen (Glasgow) DTSTART:20201126T133000Z DTEND:20201126T143000Z DTSTAMP:20260423T005804Z UID:notts_ag/38 DESCRIPTION:Title: Refined Donaldson-Thomas theory of threefold flops\nby Okke van Gard eren (Glasgow) as part of Online Nottingham algebraic geometry seminar\n\n \nAbstract\nDT invariants are virtual counts of semistable objects in the derived category of a Calabi-Yau variety\, which can be calculated at vari ous levels of refinement. An interesting family of CY variety which are of particular interest to the MMP are threefold flopping curves\, and in thi s talk I will explain how to understand their DT theory. The key point is that the stability conditions on the derived categories can be understood via tilting equivalences\, which can be seen as the analogue of cluster mu tations in this setting. I will show that these equivalences induce wall-c rossing formulas\, and use this to reduce the DT theory of a flop to a com prehensible set of curve-counting invariants\, which can be computed for s everal examples. These computations produce new evidence for a conjecture of Pandharipande-Thomas\, and show that refined DT invariants are not enou gh to completely classify flops.\n LOCATION:https://researchseminars.org/talk/notts_ag/38/ END:VEVENT END:VCALENDAR