Dear All,

The Department of Mathematics is inviting you to attend a colloquium on  February 03, 2026 (Tuesday).

Speaker: Dr. Rajesh Dey

PhD – IISER Bhopal

Teaching Fellow, Department of Mathematics, Ashoka University

Abstract: Let S_g denote the closed orientable surface of genus g, and let Mod(S_g) be its mapping class group. Then the Nielsen realization theorem asserts that any finite subgroup of Mod(S_g) acts on S_g by orientation-preserving isometries and induces a branched covering on S_g. For such covers, the Birman–Hilden theorem states that the liftable mapping class group is isomorphic to the quotient of the symmetric mapping class group by the group of deck transformations. In this talk, I will try to motivate the general liftability problem in mapping class groups through illustrative examples, and conclude by discussing some of our results for the liftability of mapping classes under alternating covers.

About the Speaker: Dr. Rajesh Dey earned his PhD from IISER Bhopal in 2025 under the supervision of Prof. Kashyap Rajeevsarathy. His research lies in the study of mapping class groups of surfaces, with a particular focus on liftable mapping class groups associated with finite-sheeted simple regular branched covers. He is currently a Teaching Fellow here at Ashoka University.