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Research at City College

Department of Mathematics

Research at City College


Research conducted in the Mathematics Department covers a broad spectrum of contemporary mathematics. Collectively, our faculty has authored many hundreds of papers, dozens of books and research monographs, and given countless talks at research seminars and conferences both in the U.S. and abroad. Current faculty research is supported by the National Science Foundation (NSF), the National Security Agency (NSA), the Office of Naval Research (ONR), the Simons Foundation, the Sloan Foundation, as well as by CUNY, through the Faculty Research Award Program. Our faculty serve as editors and on the editorial boards of leading journals, and are sought-after referees and reviewers for publications and proposals.

We present the research of the department within the framework of a segmentation of mathematics: Algebra, Analysis, Applied Mathematics, Dynamical Systems, Geometry, Number Theory, and Probability. We elaborate below on the scope of these areas as represented within the department. Of course, the nature of much current research blurs the boundaries of this classification. As a result, many individuals will be found within more than one category.

The department has several emeritus faculty who remain research active. The names of emeriti are marked with an asterisk (*) below.


The Department has a very active group working in the general area of algebra, with a focus on interactions between algebra and computer science. Sean Cleary works in combinatorial and geometric group theory, including computational aspects of questions about infinite groups. The Cryptography Lab, under the direction of Vladimir Shpilrain, does research on applications of group theory to cryptography. Prof. Shpilrain also works in statistical group theory, a recent development that brings together mathematics, statistics, and theoretical computer science. Benjamin Steinberg principally works in finite semigroup theory with a focus on applications to theoretical computer science and combinatorics. Alice Medvedev studies difference algebra from the point of view of model theory, a branch of mathematical logic.

Researcher Areas of Current Interest
Sean Cleary Geometric group theory, combinatorial group theory
Alice Medvedev Difference algebra
Vladimir Shpilrain Group theory and affine algebraic geometry
Benjamin Steinberg Semigroup theory, representation theory, algorithmic problems in infinite groups, self-similar groups
Khalid Bou-Rabee Geometric group theory, combinatorial group theory, representation theory of finitely generated groups
Zajj Daugherty Combinatorial representation theory


The Department's researchers in analysis cover an array of topics including estimation of solutions of partial differential equations using variational methods and other geometrically based techniques.

*Michael Marcus' work in probability contains numerous connections to harmonic analysis, including important work on random Fourier series. Joseph Bak has co-authored a best-selling text on complex analysis and works in approximation theory.

Researcher Areas of Current Interest
Joseph Bak Approximation theory
Pat Hooper Ergodic theory
Sergiy Merenkov Analysis on metric spaces
Bianca Santoro Geometric analysis
Christian Wolf Complex analysis, ergodic theory

Applied and Computational Mathematics

Department faculty have broad interests in applied mathematics. There is a significant expertise in algebraic cryptography - a completely new viewpoint in the design of cryptographic algorithms. Vladimir Shpilrain is active in this area. A number of researchers are interested in problems related to symbolic computation, including the two previously mentioned and *William Sit. TheCenter for Algorithms and Interactive Scientific Software has several research projects in this direction. Ethan Akin's contributions to population genetics rounds out the very extensive efforts by the department in this area.

Researcher Areas of Current Interest
Ethan Akin Population genetics
Asohan Amarasingham Theoretical and computational neuroscience
Sean Cleary Computational biology, phylogenetic algorithms
Vladimir Shpilrain Cryptography and complexity theory
Benjamin Steinberg Applications of semigroup theory to theoretical computer science

Dynamical Systems

Dynamical Systems Theory is the mathematical study of change in systems governed by a time-independent evolution rule. Arising from Newtonian physics, dynamical systems theory has been applied to all the sciences. Typical questions in the area are concerned with understanding the long term behavior of dynamical systems. Famous questions of this form include questions involving the stability of the solar system, extinction of species, and behavior of gases (the Boltzmann hypothesis).

Our faculty have interests which cover a broad array of topics in the field of pure dynamical systems.

Researcher Areas of Current Interest
Ethan Akin Topological dynamics
Pat Hooper Piecewise isometries, interval exchange transformations, ergodic theory, renormalization
Tamara Kucherenko Rotation theory
Sergiy Merenkov Complex dynamics
Christian Wolf Ergodic theory, non-uniformly hyperbolic dynamical systems, thermodynamic formalism, dimension theory, complex dynamics

Geometry and Topology

Geometric and topological ideas are pervasive in much of contemporary mathematics. The Department's research is well-represented in this area. Sean Cleary is an active researcher in geometric group theory, with a particular interest in Thompson's group. Pat Hooper works in low-dimensional topology and Teichmüller theory. Bianca Santoro works on complex geometry and geometric analysis.

*Ralph Kopperman and *Niel Shell work in areas of general topology with a variety of applications to analysis and digital imaging. Ethan Akin has published a number of research monographs in topological dynamics.

Researcher Areas of Current Interest
Ethan Akin Topological dynamics
Sean Cleary Metric geometry, cohomology of groups
Pat Hooper Low dimensional geometry, Teichmüller theory
Ralph Kopperman* General topology, asymmetric topology, non-Hausdorff topological spaces
Sergiy Merenkov Metric geometry
Bianca Santoro Complex geometry, Calabi-Yau manifolds
Khalid Bou-Rabee Profinite groups

Number Theory

Number theory has its origins in ancient problems related to the study of whole number solutions to polynomial equations. The research of the number theorists in the department is unified by the common theme of counting (or parametrizing) objects of arithmetic interest, be they points on curves, or lengths of geodesics on a surface, or conjugacy classes in reductive groups.

Researcher Areas of Current Interest
Joseph Bak Diophantine equations
Gautam Chinta Number theory, automorphic forms, L-functions
Brooke Feigon Number theory and automorphic forms
Jay Jorgenson Analytic number theory, trace formulas
Alice Medvedev Arithmetic dynamics

Probability and Statistics

*Michael Marcus' research is in stochastic processes, particularly Gaussian and Markov processes and their interrelationships. *Mark Brown works on a variety of problems in both probability and statistics revolving around approximation methods with error bounds. Joseph Bak is exploring certain questions in classical probability.

Vladimir Shpilrain and his collaborators have applied probabilistic methods to analyze the complexity of algorithms in algebra and logic.

Researcher Areas of Current Interest
Asohan Amarasingham Non-stationary point processes, conditional and simultaneous inference, and applications to neurophysiology
Joseph Bak Classical probability
Vladimir Shpilrain Average-case and generic-case complexity of algorithmic problems
Christian Wolf Ergodic theory
Jack Hanson Percolation/random graphs, sandpiles/other cellular automata, and issues from mathematical statistical physics