Dear colleagues,

I should be pleased to announce the following intensive seminar at IPMU
(the Institute for the Physics and Mathematics of the Universe).

Best Regards,

Yuji Sano
(IPMU)
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Date: 4 (Mon) August, 2008, 13:00 -- 14:30 and 15:30 -- 17:00

Place: Seminar Room at Prefab. B, Kashiwa Campus, the University of Tokyo.

Speaker: Kentaro Nagao (Kyoto University)

Title: Counting invariants of perverse coherent systems on CY 3-folds and
their wall-crossings

Abstract: A perverse coherent system on a CY 3-fold is a pair of perverse
coherent sheaf on the CY 3-fold and a morphism to it from the
structure sheaf.
We intruduce moduli spaces of perverse coherent systems and counting
invariants of them.
In order to construct a moduli space we should choose a parameter of stability.
We show that Donaldson-Thomas theory and Pandharipande-Thomas theory
can be recovered at specific parameters.
We also establish wall-crossing formulas for the generating functions
of counting invariants of perverse coherent systems.
As applications, we provide some formulas on DT invariants and PT invariants.
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Please notice that the seminar will be held at the "Prefab" of IPMU.
It is located at the next of the prefab of "Frontier Sciences,
Computational Biology"
(情報生命科学実験棟).
You can check the location from

http://www.ipmu.jp/access/img/KashiwaCampusMap.png

The schedule of the seminar can be checked from

http://www.ipmu.jp/seminars/