I am a Professor of Mathematics at Brandeis University
Contact:
Email: kleinboc [at] brandeis.edu
Office: Goldsmith 207
Mailing address: Brandeis University, Department of Mathematics, MS 050, 415 South Street, Waltham, MA 02453, USA
Short Bio:
I completed my Ph.D. at Yale University in 1996 under the supervision of Grigory Margulis. After a postdoc at the Institute for Advanced Study in Princeton, NJ (supervised by Jean Bourgain), I joined the Mathematics Department of Rutgers University (New Brunswick, NJ) as a Hill Assistant Professor in 1997. I joined Brandeis University in 2000, becoming Full Professor of Mathematics in 2008 and Theodore and Evelyn G. Berenson Chair in Mathematics in 2024.
Research interests:
Lie groups, discrete subgroups and homogeneous spaces
Ergodic theory and dynamical systems
Metric Diophantine approximation
Most recent publications
(see also my papers on arxiv.org and the link at the top of the page to access all my publications):
Uniform Diophantine approximation with restrictions via total density of collections of subspaces (with L. Hong and V. Neckrasov), Preprint (2026), arXiv:2603.25988.
Constructing bounded orbits of special types on homogeneous spaces (with M. Einsiedler and A. Rao), Preprint (2025), arXiv:2511.16095.
Simultaneously bounded and dense orbits for commuting Cartan actions (with C. Wu), Preprint (2025), arXiv:2509.05272.
Submanifold-genericity of R^d-actions and uniform multiplicative Diophantine approximation (with P. Bandi and R. Fregoli), Preprint (2025), arXiv:2504.02258.
On multiplicatively badly approximable vectors (with R. Fregoli), J. Number Theory 278 (2026), 570–621.
Singularity, weighted uniform approximation, intersections and rates (with N. Moshchevitin, J. Warren and B. Weiss), Compositio Math. 161 (2025), no. 11, 2990–3016.
Dimension drop for escape on average in homogeneous spaces (with S. Mirzadeh), Discrete Contin. Dyn. Syst. 45 (2025), no. 5, 1653–1671.
Dimension drop for diagonalizable flows on homogeneous spaces (with S. Mirzadeh), J. Mod. Dyn. 20 (2024), 441–478.
Selected video presentations:
Well approximable Dirichlet spectrum and full Hausdorff dimension of the Folklore Set (Banach Center, Warsaw, May 2026)
Dimension Drop Conjecture in Homogeneous Dynamics (ICTS, Bangalore, December 2022)
Shrinking targets on homogeneous spaces and improving Dirichlet's Theorem (Number Theory Web Seminar, March 2022)
Khintchine-type theorems for values of homogeneous polynomials at integer points: lectures 1, 2, 3 (ICTS, Bangalore, September 2019)
Shrinking targets on homogeneous spaces and improving Dirichlet's Theorem (CIRM, Luminy, February 2017)
Hyperbolic dynamics and intrinsic Diophantine approximation (HSE, Moscow, May 2016)
Hausdorff dimension estimates for bounded orbits on homogeneous spaces of Lie groups (Isaac Newton Institute, Cambridge, July 2014)
Recently graduated students:
Jiajie Zheng (2023)
Mishel Skenderi (2021)
Anurag Rao (2020)
Shahriar Mirzadeh (2018)
Editorial boards:
Support:
NSF Grant DMS-2155111
Simons Foundation Research Fellowship (2014-2015 and 2022)
BSF Grant 2016256
A short fun video: Powers of two on the Numberphile Channel, with extra footage