Jae Choon Cha is Professor of Mathematics and Mueunjae Chair Professor at POSTECH.  He is also an Affiliate Professor at KIAS.

 2017 Fall On sabbatical leave (Max Planck Institute for Mathematics)
1. Hirzebruch-type invariants of Cheeger-Gromov and low dimensional topology, Oberseminar at Max Planck Institute for Mathematics, August 31, 2017, Bonn, Germany.
2. Bordism, chain homotopy, and Cheeger-Gromov $\rho$-invariants, Quantitative Geometry and Topology — a special session in Mathematical Congress of America 2017, July 25, 2017, Montreal, Canada.
3. 다양체의 위상수학과 디스크 임베딩 (Topology of manifolds and disk embedding), 무은재 석좌교수 기념강연 (Mueunjae Chair Professor Lecture), May 22, 2017, POSTECH, Pohang, Korea.
4. Whitney towers in a rational homology ball, Invariants in Low-dimensional Topology, May 12, 2017, KIAS, Seoul, Korea.
5. Milnor invariants and rational Whitney towers, April 19, 2017, Indiana University, Bloomington, Indiana, USA.
6. $L^2$-acyclic bordism and Whitney towers, The 12th East Asian School of Knots and Related Topics, February 14, 2017, University of Tokyo, Japan.
7. Disk embedding in dimension four, The 2nd KAST and Lincei bilateral symposium, December 6, 2016, Seoul, Korea.
8. Mathematics of dimension 4, KAIST CMC Noon Lecture, December 2, 2016, KAIST, Daejeon, Korea.
9. A quantitative approach to Cheeger-Gromov rho invariants and 4-dimensional bordism, October 25, 2016, Hausdorff Research Institute for Mathematics, Bonn, Germany.
10. 4-dimensional $L^2$-acyclic bordism and Whitney towers, Conference on 4-manifolds and knot concordance, October 17, 2016, Max Planck Institute for Mathematics, Bonn, Germany.
Research on Geometric Topology
• Interplay between topology of dimension 3 and 4
• Knot theory: placement problems of manifold pairs
• Related algebra, homotopy theory, and $L^2$-invariants

KnotInfo: a table of invariants of classical knots, maintained by Charles Livingston and me.

### List of all papers

1. Unknotted gropes, Whitney towers, and doubly slicing knots (with Taehee Kim)
Transactions of the American Mathematical Society, to appear.
• Preprint arXiv:1612.02226 (43 pages)
2. Rational Whitney tower filtration of links
Mathematische Annalen, to appear.
3. Whitney towers and abelian invariants of knots (with Mark Powell and Kent E. Orr)
• Preprint arXiv:1606.03608 (34 pages)