Thomas Koberda


Assistant Professor of Mathematics

E-mail: firstname dot lastname at gmail dot com

Office: Kerchof 304

Mailing Address:
Department of Mathematics
University of Virginia
P. O. Box 400137
Charlottesville, VA 22904-4137 USA

Here is my CV: pdf


I am currently teaching Mathematics 4840 (Introduction to Mathematical Research).

I taught a topics course on right-angled Artin groups at Yale in the spring of 2013. Here are some course notes.


I co-organized the Virginia Topology Conference 2016, which took place November 18-20, 2016. Here is a link.


My research is best described as geometric group theory. I am especially interested in mapping class groups of surfaces, right-angled Artin groups, and one-dimensional dynamics. I am also interested in the geometry and topology of 3-manifolds, and have recently become interested in the topology of arrangements.

Here are my research papers, in the order that they were written. In an effort to spam the arXiv as little as possible, the pdf versions on the UVa server (when available) are more up-to-date than the arXiv versions.

31. "Free products and the algebraic structure of diffeomorphism groups." Joint with Sang-hyun Kim. (Submitted) pdf

30. "Actions of right-angled Artin groups in low dimensions." (Handbook of Group Actions (ed. L. Ji, A. Papadopoulos and S.-T. Yau), International Press and Higher Education Press, to appear) pdf

29. "Two-chains and square roots of Thompson's group F." Joint with Yash Lodha. (Submitted) pdf

28. "Representations of surface groups with finite mapping class group orbits." Joint with Indranil Biwas, Mahan Mj, and Ramanujan Santharoubane. (Submitted) pdf

27. "Irreducibility of quantum representations of mapping class groups with boundary." Joint with Ramanujan Santharoubane. (Submitted) pdf

26. "Chain groups of homeomorphisms of the interval and the circle." Joint with Sang-hyun Kim and Yash Lodha. (Submitted) pdf Shortened version

25. "Rotation spectra and exotic group actions on the circle." Joint with Sang-hyun Kim and Mahan Mj. (Submitted) pdf

24. "Residually finite rationally p groups." Joint with Alexander I. Suciu. (Submitted) pdf

23. "A representation theoretic characterization of simple closed curves on a surface." Joint with Ramanujan Santharoubane. (To appear in Math. Res. Lett.) pdf

22. "Unsmoothable group actions on compact one-manifolds." Joint with Hyungryul Baik and Sang-hyun Kim. (To appear in J. Eur. Math. Soc.) pdf

21. "Quotients of surface groups and homology of finite covers via quantum representations." Joint with Ramanujan Santharoubane. (Invent. Math. 206 (2016), 269-292) pdf

20. "The geometry of purely loxodromic subgroups of right-angled Artin groups." Joint with Johanna Mangahas and Samuel J. Taylor. (To appear in Trans. Amer. Math. Soc.) pdf

19. "Injective maps between flip graphs." Joint with Javier Aramayona and Hugo Parlier. (Ann. Inst. Fourier 65 (2015), no. 5, 2037-2055) pdf

18. "Right-angled Artin subgroups of the C diffeomorphism group of the real line." Joint with Hyungryul Baik and Sang-hyun Kim. (Israel J. Math. 213 (2016), no. 1, 175182) pdf

17. "Anti-trees and right-angled Artin subgroups of planar braid groups." Joint with Sang-hyun Kim. (Geom. Topol. 19 (2015), no. 6, 3289-3306) pdf

16. "An effective algebraic detection of the Nielsen-Thurston classification of mapping classes." Joint with Johanna Mangahas. (J. Top. Analysis 7 (2015), no. 1, 1-21) pdf

15. "Right-angled Artin groups and finite subgraphs of curve complexes." Joint with Sang-hyun Kim. (Osaka J. Math. 53 (2016), 705716) pdf

14. "The geometry of the curve graph of a right-angled Artin group." Joint with Sang-hyun Kim. (Int. J. Algebra Comput. 24 (2014), no. 2, 121-169) pdf

13. "An obstruction to embedding right-angled Artin groups in mapping class groups." Joint with Sang-hyun Kim. (Int. Math. Res. Not. IMRN 2014, no. 14, 3912-3918) pdf

12. "Alexander varieties and largeness for finitely presented groups." (J. Homotopy Rel. Structures 9 (2014), no. 2, 513-531) pdf

11. "Teichmüller polynomials, Alexander polynomials and finite covers of surfaces." (Preprint) pdf

10. "Embedability between right-angled Artin groups." Joint with Sang-hyun Kim. (Geom. Topol. 17 (2013), no. 1, 493-530) pdf Appendix

9. "Ping-pong lemmas with applications to geometry and topology." (Geometry, topology and dynamics of character varieties, 139-158, Lect. Notes Ser. Inst. Math. Sci. Natl. Univ. Singap., 23, World Sci. Publ., Hackensack, NJ, 2012) I cannot post this paper on my website due to the copyright agreement.

8. "Faithful actions of automorphisms on the space of orderings of a group." (New York J. Math. 17 (2011) 783-798) pdf

7. "Right-angled Artin groups and a generalized isomorphism problem for finitely generated subgroups of mapping class groups." (Geom. Funct. Anal. 22 (2012), no. 6, 1541-1590) pdf

6. "Entropy of automorphisms, homology and the intrinsic polynomial structure of nilpotent groups." (In the tradition of Ahlfors-Bers. VI, 87-99, Contemp. Math., 590, Amer. Math. Soc., Providence, RI, 2013) pdf

5. "Residual properties of fibered and hyperbolic 3-manifolds." (Topology Appl. 160 (2013), no. 7, 875-886) pdf

4. "Effective indices of subgroups in one-relator groups with free quotients." (Comm. Alg. 39 (2011), no. 11, 4336-4341) arXiv link

3. "Asymptotic linearity of the mapping class group and a homological version of the Nielsen-Thurston classification." (Geom. Dedicata 156 (2012), 13-30) Geometriae Dedicata link

2. "On ergodic transformations that are both weakly mixing and uniformly rigid." Joint with J. James, K. Lindsey, C.E. Silva and P. Speh. (New York Journal of Mathematics 15 (2009) 393-403) NYJM link

1. "Measurable Sensitivity." Joint with J. James, K. Lindsey, C.E. Silva and P. Speh. (Proceedings of the American Mathematical Society 136 (2008) 3549-3559) Proceedings link

Non-original work and writings unsuitable for publication

1. "Class field theory and the MKR dictionary for knots." This was my minor thesis at Harvard. I am not a number theorist and I expect that there are many mistakes and inaccurate statements contained therein. It is expository and does not contain many proofs. pdf

2. "Notes on recent work of Dani Wise." These are some recent expository notes which contain a new theorem as well. This is a new version, fixing two minor errors in the first version. The corrections are: 1. one needs a relative version of the main theorem to establish virtual fibering of cusped hyperbolic 3-manifolds, and 2. graph groups are residually finite rationally solvable, but it is not because they are residually torsion-free nilpotent. pdf

3. "Representations of Galois Groups on the Homology of Surfaces." Joint with A. Silberstein. arXiv link

4. "On some of the residual properties of finitely generated nilpotent groups." pdf, arXiv link