##### Department of Mathematics,

University of California San Diego

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### Math 208 - Algebraic Geometry Seminar

## Jeongseok Oh

#### Korea Institute for Advanced Study

## Counting sheaves on Calabi-Yau 4-folds

##### Abstract:

We define a localised Euler class for isotropic sections, and isotropic cones, in SO(N) bundles. We use this to give an algebraic definition of Borisov-Joyce sheaf counting invariants on Calabi-Yau 4-folds. When a torus acts, we prove a localisation result. This talk is based on the joint work with Richard. P. Thomas.

Host: Michail Savvas

### November 6, 2020

### 3:30 PM

### Contact David Stapleton, dstapleton@ucsd.edu, for zoom info.

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