Time: July, 14th, 1:30-2:30PM Room: Carslaw, 707A Speaker: Yi Ni (Assistant Professor at California Institute of Technology) Speaker’s Homepage: http://www.its.caltech.edu/~yini/ Title of talk: Cosmetic Surgeries on Knots in $S^3$ Abstract: Two Dehn surgeries on a knot are called purely cosmetic, if they yield manifolds that are homeomorphic as oriented manifolds. I will talk about necessary conditions for the existence of purely cosmetic surgeries on knots in $S^3$. In particular, the two surgery slopes must be the opposite of each other. The proof uses a surgery formula for the correction terms in Heegaard Floer homology. This is joint work with Zhongtao Wu.