## Calendar

**Departmental Events, Spring 2014:**

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

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**

MomentsÂ 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
boundaryÂ
and derive a formula for theÂ momentsÂ ofÂ Â the
associatedÂ randomÂ variableÂ in terms of the orthospectrum.Â
We show thatÂ Â the the first twoÂ momentsÂ correspond to two cases of
known identities of Basmajian andÂ the author. We further obtain an
explicit formula in terms of theÂ Â trilogarithm functions for the
average time for the geodesic flow to hitÂ Â the boundary in the surface
case, using the thirdÂ moment. This is jointÂ 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 metricsÂ asÂ a polyhedral
fan. Outputs of distance-based tree reconstruction algorithms
suchÂ asÂ 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. Â This is joint work with Seth Sullivant.Â *

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

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
guaranteeÂ 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 masterâ€™s andÂ 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. Alonsoâ€™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. Â 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'. Â 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

*abstract*

**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. Â 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: Jun 2, 2014