Department of Mathematics and Computer Science



Departmental Events,


Fall 2014:

November 14-15, Hackathon 2014.



Lehman College (CUNY)
Student Life Building
250 Bedford Park Blvd W
Bronx, NY 10468

DETAILS: This competition brings together technology, professional networking, team building skills and the awesome opportunity to win prizes. Goldman Sachs will attend the event to recruit students and to judge the presentations. Teams of 5 will create solutions to challenging problems using technology.



Spring 2014:

Monday, 2 June 2014, noon, Room TBA: Department Colloquium
Francesco Matucci
Center for Algebra
University of Lisbon

Conjugacy, dynamics and subgroups in Thompson groups


Wednesday, 28 May 2014, 1:30pm Room TBA: Department Colloquium
Tari Hoang Le
Department of Mathematics
University of Texas, Austin

Polynomial configurations in the primes
The Green-Tao theorem says that the primes contain arithmetic progressions of arbitrary length. Tao and Ziegler extended it to polynomial progressions, showing that congurations {a+P_1(d),... , a+P_k(d)} exist in the primes, where $P_1, \ldots, P_k$ are polynomials in Z[x] without constant terms (thus the Green-Tao theorem corresponds to the case where all the P_i are linear). We extend this result further, showing that we can add the extra requirement that d be of the form p-1 (or p + 1) where p is prime. This is joint work with Julia Wolf.


Wednesday, 21 May 2014, 1:30pm Room Gillet 205: Department Colloquium
Martin Bridgeman
Department of Mathematics
Boston College

Moments of the boundary hitting function for geodesic flow
We consider the distribution of the time for the geodesic flow to hit the boundary of a hyperbolic manifold with geodesic boundary  and derive a formula for the moments of  the associated random variable in terms of the orthospectrum.  We show that  the the first two moments correspond to two cases of known identities of Basmajian and the author. We further obtain an explicit formula in terms of the  trilogarithm functions for the average time for the geodesic flow to hit  the boundary in the surface case, using the third moment. This is joint work with S. P. Tan.


Monday, 19 May 2014, 1pm Room Gillet 205: Department Colloquium
Marian Gidea
Department of Mathematics
Yeshiva University

Arnold Diffusion in Celestial Mechanics

Wednesday, 14 May 2014, 3pm Room TBA: Department Colloquium
Ruth Davidson
Department of Mathematics
North Carolina State University

Distance-based phylogenetic methods near a polytomy
A phylogenetic tree models the common evolutionary history of a group of species. A tree metric is a distance function on a set of species realized by a tree with edge weights. Distance-based phylogenetic algorithms attempt to solve the NP-hard least-squares phylogeny problem by mapping an arbitrary dissimilarity map representing biological data to a tree metric. The set of all dissimilarity maps is a Euclidean space properly containing the space of all tree metrics as a polyhedral fan. Outputs of distance-based tree reconstruction algorithms such as UPGMA and Neighbor-Joining are points in the maximal cones in the fan. Tree metrics with polytomies, or internal vertices of degree higher than three, lie at the intersections of maximal cones. A phylogenetic algorithm divides the space of all dissimilarity maps into regions based upon which combinatorial tree is reconstructed by the algorithm. We use polyhedral geometry to compare the local nature of the subdivisions induced by least-squares phylogeny, UPGMA, and Neighbor-Joining. Our results suggest that in some circumstances, UPGMA and Neighbor-Joining poorly match least-squares phylogeny when the true tree has a polytomy.  This is joint work with Seth Sullivant. 


Monday, 12 May 2014, 3pm Room TBA: Department Colloquium
Bushra Anjum
National University of Computer and Emerging Sciences

Analyzing the work in Net"work"s
Dr. Bushra Anjum will be discussing the structure and characteristics of large scale networks with special emphasis on two of the most prominent and prevalent networks of our time, the Internet and the Social network. Though microscopically different, both networks (when studied as graphs consisting of nodes and edges) share some macroscopic structural properties. She will then formulate two research problems. First, focusing on the Internet, how to formulate a path that can guarantee certain quality measures to the traffic traversing on it. And second, focusing on the Social network, how to mathematically model a contagion spread in various social networks such as facebook, linkedIn, g+ etc.


Thursday, 8 May 2014, 3pm Room Gillet 227: Department Colloquium
Weijia Xu
Texas Advanced Computing Center
University of Texas

Facilitating Data-driven Discovery through High Performance Computing and Visualization
As gathering and creating data has become increasingly easier in recent years, data deluge emerges in both everyday life and scientific research. Despite opportunities presented for new data-driven discovery, it has however become a challenge to find (and re-find) the most relevant information amidst multitudes of data. This challenge requires solutions in two folds: 1) efficiency in processing and analyzing large scale data sets and 2) effectiveness in transforming analytic results into insights for domain researchers and decision makers. For the former, new computational methods must be developed to leverage distributed computational infrastructure for a solution scalable with input data size. The latter aspect can be addressed through visualization techniques which enable users to directly interact with the data and relevant analytic results. In this talk, I will present two project examples combining data intensive computing and visual analytic method to address this very issue. The first project example leverages Map Reduce framework to help researchers identify interesting structures from large scale simulated astronomical data set. The second project example illustrates how visual analytic methods effectively assist human users accessing, analyzing and deriving insight from a large-scale archival record collection.


Monday, 5 May 2014, 3pm Room Gillet 231: CSM Workshop
Dana Smith
Computer Science Major
Lehman College

Learning Outside the Classroom
The final CSM workshop will feature CSM Scholar Dana Smith. She will give a talk about winning a recent hackathon competition sponsored by Google and Intel and the benefits of joining an engineering organization. She will talk about her experience while attending a STEM convention last month and opening a chapter of an engineering organization at Lehman College.


Wednesday, 28 April 2014, 3pm Room G 227: Department Colloquium
Javier Alonso Lopez
Department of Computer Science
Duke University

Software faults, failures and their consequences: What we can learn from and do about them? Abstract: Software failures and their underlying bugs are one of the most prevalent causes of system outages. New development methodologies, automatic testing, source code checking, and more sophisticated debugging techniques have been successful to significantly reduce the number of software bugs present when delivered for operation. Two main factors are responsible for a non-negligible fraction of bugs being still present during operation with potentially catastrophic consequences: 1) the market pressure of deploying new services and features as soon as possible and 2) the growing software complexity to provide the services required by the market. So, the question arises: What can we do about these software bugs during operation? Software faults have been classified according to different characteristics. We propose a new classification based on the software faults characteristics more than the type of triggers that make the software bug surface or the type of the software failure: classifying them into Bohrbugs and Mandelbugs. This theoretical classification has a practical consequence: Each type of bug requires different mitigation techniques. A detailed study of software failures of 8 JPL/NASA missions will be presented analyzing the software bugs, failures and their mitigations from different aspects. The results of this study and the techniques used to perform it are being piloted at JPL as part of a continuous improvement effort, the goal of which is to improve the understanding and management of failure behavior for the robotic spacecraft deployed by JPL. Finally, I will discuss aging-related bugs (a subset of Mandelbugs) and I will present different experimental research evaluating different software rejuvenation approaches such as the ones based on machine learning algorithms to predict software failures caused by aging-related bugs.
Biography: Javier Alonso received the master’s and  Ph.D. degrees in Computer Science from the Technical University of Catalonia (Universitat Politecnica de Catalunya, UPC, Spain) in 2004 and 2011, respectively. From 2006 to 2011, he held an assistant lecturer position in the Computer Architecture Department of UPC. Since 2011, he has been a Postdoctoral Associate under the mentoring of Prof. Kishor S. Trivedi, in the Electrical and Computer Engineering Department at Duke University. Dr. Alonso’s research interests are in software engineering and distributed systems with special attention to dependability, availability, resilience and software rejuvenation. His main goal is developing mechanisms to deal with software faults and their consequent failures during operation to guarantee high-quality of service to the end users. He has been involved in JPL/NASA, NATO, NEC, Huawei and WiPro funded projects.


Wednesday, 24 April 2014, 3pm Room Gillet 227: Department Colloquium
Jonathan Voris
Department of Computer Science
Columbia University

Modeling User Behavior for Active Authentication


Monday, 24 February 2014, 11am, Gillet 311: Department Colloquium
Prof. Anthony Gamst
Department of Biostatistics and Bioinformatics
University of California, San Diego

Some Problems in the Analysis of High-Dimensional Models
Models with large numbers of nuisance parameters are common in modern statistics, having applications in laboratory medicine, econometrics, genomics, medical imaging, physics, epidemiology, and many other areas. Classical techniques, including Maximum Likelihood and Bayesian approaches, often produce sub-optimal or even inconsistent estimates of the parameters of interest in these models, while asymptotically unbiased estimating equations work rather generally. We study several such models, identify the sources of bias and spurious correlation which lead to inconsistency or sub-optimality, and compute the minimal smoothness required for the existence of root-n consistent (and efficient) parameter estimates. We also examine simultaneous estimation of nuisance parameters and parameters of interest. These results are related to every-day practice, particularly to the analysis of regression models with many predictors, and some heuristics are given.


Monday, 10 February 2014, 11am, Gillet 311: Department Colloquium
Prof. Erik Guentner
Department of Mathematics
University of Hawai'i

Geometry and noncommutative duals of groups
Nonommutative geometry, in the sense of Alain Connes, proceeds from the observation that properties of a topological space are reflected by properties of the algebra of functions on it.  Further, in cases when the natural topological space is poorly behaved it may be profitably be replaced by a noncommutative C*-algebra, the algebra of 'functions on a noncommutative space'.  In the talk I will survey results relating geometric properties of a discrete group to its harmonic analysis as manifested by the noncommutative dual space of the group.


Thursday, 6 February 2014, 2pm, Gillet 311: Department Colloquium
Prof. Loredana Lanzani
Department of Mathematics
University of Arkansas

Harmonic Analysis Techniques in Several Complex Variables


Monday, 3 February 2014, 11am, Gillet 219: Department Colloquium
Prof. Michael Usher
Department of Mathematics
University of Georgia

The geometry of the Hamiltonian diffeomorphism group
An important object associated to any symplectic manifold is its infinite-dimensional group of "Hamiltonian diffeomorphisms," consisting of those diffeomorphisms which arise as time-evolution maps in a generalization of Hamilton's formulation of classical mechanics. Rather unusually for an infinite-dimensional Lie group, the Hamiltonian diffeomorphism group admits a bi-invariant metric induced by a norm on its Lie algebra, discovered by Hofer, which can be viewed as giving a coordinate-independent measurement of the "energy" of any Hamiltonian diffeomorphism.  I will discuss some progress in understanding this still-rather-mysterious metric, concerning for instance whether it is always unbounded and how it interacts with submanifolds, and will also touch on some open questions.


Monday, 27 January 2014, 11am, Gillet 219: Department Colloquium
Prof. David Savitt
Department of Mathematics
Brown University

Galois representations
The absolute Galois group of the field of rational numbers is a fundamental object of study in number theory. I will begin by giving a tour of the representation theory of this group, with an emphasis on representations in characteristic p. In the second half of the talk I will describe my recent work with Gee, Liu, and others on generalizations of the weight part of Serre's conjecture.


Friday, 24 January 2014, 11am, Gillet 219: Department Colloquium
Prof. Bianca Viray
Department of Mathematics
Brown University

The local to global principle for rational points
Let X be a connected smooth projective variety over Q. If X has a Q point, then X must have local points, i.e. points over the reals and over the p-adic completions Q_p. However, local solubility is often not sufficient. Manin showed that quadratic reciprocity together with higher reciprocity laws can obstruct the existence of a Q point (a global point) even when there exist local points. We will give an overview of this obstruction (in the case of quadratic reciprocity) and then show that for certain surfaces, this reciprocity obstruction can be viewed in a geometric manner. More precisely, we will show that for degree 4 del Pezzo surfaces, Manin's obstruction to the existence of a rational point is equivalent to the surface being fibered into genus 1 curves, each of which fail to be locally solvable. This talk will be suitable for a general audience.


Friday, 24 January 2014, Carman Hall, 11am: CMACS Talk
Prof. Bud Mishra
Courant Institute of Mathematical Sciences
New York University







Last modified: Oct 22, 2014

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