DATE

SEMINAR

SPEAKER

TITLE

Thur. Jan. 23

Algebra
1:30-2:30
RH 222

Greg Marks

"Perfect rings and chain conditions."

Thur. Jan. 30

Algebra
1:30-2:30
RH 222

Greg Marks

"Perfect rings and chain conditions."

Thur. Jan. 30

Topology & Geometry
3:45-4:45
RH 134

Kevin Scannell

"Bending deformations of hyperbolic 3-manifolds"

Abstract: I will give introduction to joint work with Anneke Bart on "bending deformations" of hyperbolic 3-manifolds.

Fri. Jan. 31

Computer Science
4:10 - 5:00
RH 316

Dr. Ann McNamara
Trinity College Dublin
Host: Kim Druschel

" Psychophysical Experimentation in Computer Graphics"

Abstract: Increased application of computer graphics in areas which demand high levels of realism has made it necessary to examine the manner in which images are evaluated and validated. In this talk, we explore the need for including the human observer in any process which attempts to quantify the level of realism achieved by the computer graphics process, from measurement to display.
We introduce a framework for measuring the perceptual equivalence (from a lightness perception point of view) between a real scene and a computer simulation of the same scene. Because this framework is based on psychophysical experiments, results are produced through study of vision from a human vision, rather than a machine vision, point of view. This framework can then be used to evaluate, validate and compare rendering techniques. Data gathered through such experimentation can also be used to accelerate computer graphics algorithms. There may be little point spending time or resources to compute detail in an image that would not be detected by a human observer. By eliminating any computation spent on calculating image features which lie below the threshold of visibility, computation times can be shortened - leading to more efficient processing. We are now working to develop experiments that detect threshold visual differences between images and their real world counterpart, and ultimately aim to use these results to direct graphics algorithms to work on those parts of an image that are in most need of refinement., without sacrificing visual quality.
This talk will give a detailed description of the construction of an experimental framework that enables human observers to perform the light matching task in real scenes and computer generated representations. Task performance in each case (real versus graphic) can then be compared to give a measure of perceptual equivalence. To illustrate key concepts and results, a case study, involving comparing a test environment, consisting of a small room containing several objects, to its graphical counterpart, will be discussed.

There will be a reception in RH 114 from 3:50 until 4:10.

Mon. Feb. 3

Computer Science
4:10 - 5:00
RH 320

Dr.Michael H. Goldwasser
Loyola State University
Host: Kim Druschel

" Linear-Time Algorithms for Computing Maximum-Density Sequence Segments with Bioinformatics Applications"

Abstract: We study an abstract optimization problem arising from biomolecular sequence analysis. One motivation is the desire to identify GC-rich segments of DNA sequences. For a sequence A = {a1, a2, ..., an} of real numbers, a segment A(i,j) is a consecutive subsequence of A starting with index i and ending with index j. The maximum-density segment problem takes A and two values L and U as input and asks for a segment of A with the largest possible density among those of width at least L and at most U. We provide a relatively simple, O(n)-time algorithm for this problem. This improves upon the O(n log L)-time algorithm by Lin, Jiang and Chao, for the case where U is unbounded, and upon a trivial O(n(U-L+1))-time algorithm when both L and U are specified. This is joint work with Ming-Yang Kao and Hsueh-I Lu.

There will be a reception in RH 320 from 4:00 until 4:10.

Wed. Feb 5

Math/CS Club
4:10-5:00
RH 237

David Letscher

Ready, Aim, Fire!!!
Parallel Processing and the Firing Squad Synchronization Problem

Pizza and Other Refreshments will be served before the talk.

Thur. Feb 6

Algebra
1:30-2:20
RH 222

Greg Marks

"2-primal rings and the Zariski topology."

Thur. Feb 6

Analysis
2:30-3:30
RH 128

Dr. Gestur Olafsson
Louisiana State University
Host: Darrin Speegle

" Wavelets, Frames, and Representation Theory"

Thur. Feb 6

Topology & Geometry
3:45-4:45
RH 134

Kevin Scannell

"Bending deformations of hyperbolic 3-manifolds" Cont'd

Fri. Feb 7

Computer Science
4:10 - 5:00
RH 316

Dr. Rajiv Ghandi
University of Maryland
Host: Kim Druschel

Approximation Algorithms for Broadcast Scheduling.

Abstract: We will study a problem that arises in pull-based data dissemination systems, where information requested by clients is delivered via a broadcast channel. Client requests arrive over time. Broadcasting can exploit overlap among the client requests to reduce load. Thus, if multiple clients make a request for the same data then the server can satisfy the requests in one broadcast. We consider the broadcast scheduling problem in which the client requests at different times are known in advance and our goal is to schedule the broadcasts so as to minimize the total response time.

This problem is NP-hard. We present approximation algorithms for this problem. We also describe general paradigms underlying our work and discuss the broader applicability of the techniques.

There will be a reception in RH 114 from 3:50 until 4:10.

Mon. Feb 10

Analysis
4:10 - 5:00
RH 320

Dr. Salem Ben Said
Host: Brad Currey

Fatou's theorems and Hardy-type spaces for eigenfunctions of the invariant differential operators on symmetric spaces.

Abstract: Let X be a Riemannian symmetric space of the noncompact type. Each eigenfunction of invariant differential operators on X can be represented as a Poisson transform of a hyperfunction on the maximal boundary of X . This was conjectured by Helgason and proved by Kashiwara et al.. Since then, it has becomes natural to characterize the range of the Poisson transform on classical spaces. In this talk, using a Fatou-type theorem, I characterize the image of the Poisson transform of L p -functions on the boundary , as a Hardy-type space on X .

There will be a reception in RH 320 from 3:50 until 4:10.

Tues. Feb 11

Analysis
2:10 - 3:00
RH 222

Brad Currey

"Generalities, and Examples of Wavelet-type Homogeneous Spaces"

Thur. Feb 13

Algebra
1:30-2:30
RH 222

Greg Marks

"2-primal rings and the Zariski topology."

Thur. Feb 13

Topology & Geometry
3:45-4:45
RH 134

Dr. Eugenie Hunsicker
Lawrence College
Host: Brian Clair

"L^2 Hodge theorems for manifolds with fibration boundaries"

Fri. Feb 14

Colloquium
11:00-11:50
Rh 316

Dr. Eugenie Hunsicker
Lawrence College
Host: Brian Clair

"L^2 Hodge theorems: Why weight?"

Tues. Feb 18

Analysis
2:10 - 3:00
RH 222

Brad Currey

Explicit Examples of Wavelet-type Homogeneous Spaces

Thur. Feb 20

Algebra
1:30-2:30
RH 222

Greg Marks

"2-primal rings and the Zariski topology."

Fri. Feb 21

Analysis
4:10 - 5:00
RH 320

Dr. Demetrio Labate
Host: Darrin Speegle

"A Unified Theory of Reproducing Function Systems"

Abstract: By a reproducing method for a Hilbert space H we mean the use of two countable families {e_j : j in J}, {f_j: j in J}, in H , so that the first analyzes a function h in H by forming the inner products {<h, e_j >: j in J }, and the second reconstructs h from this information: h = S_{j in J} <h, e_j > f_j .

A variety of such systems have been used successfully in both pure and applied mathematics. They have the following feature in common: they are generated by a single or a finite collection of functions by applying to the generators an apprpriate set of dilations modulations, and translations.
The Gabor systems, for example, involve a countable collection of modulations and translations; the affine systems (that produce a variety of wavelets) involve translations and dilations. Considerable amount of research has been conducted in order to characterize those generators of such systems. In this talk we present an approach that unifies all of these characterizations by means of a relatively simple system of equalities. We also describe how our methods apply to various affine-like, wave packets and Gabor systems.

There will be a reception in RH 320 from 3:50 until 4:10.

Thur. Feb 20

Topology & Geometry
3:45-4:45
RH 134

Anneke Bart

"Computing Cuspidal Cohomology"

Abstract: Bending Deformations may be studied by computing cuspidal cohomology with twisted coefficients. Several methods are available for this computation. I will describe how to use the Mendoza Complex for Bianchi Orbifolds and their quotient manifolds to compute the cuspidal cohomology. Examples will include the figure eight knot complement and a 2 component link whose fundamental group is a subgroup of the Bianchi Group PSL₂(O₇). (I will of course start by explaining what a Bianchi group and a Mendoza Complex is.)

Fri. Feb 21

Analysis
4:10 - 5:00
RH 222

Dr. Marcin Bownick
Host: Darrin Speegle

"How to construct multidimensional wavelets with good time-frequency localization?"

Abstract: In this talk I will discuss the problem of constructing orthogonal wavelets in higher dimensions. In general this is a difficult problem if we require some special properties on wavelets, such as regularity or fast decay. I will present some positive results on the existence of regular wavelets. I will also describe certain inherent limitations on the existence of wavelets with good time-frequency localization.

Tue. Feb 25

Analysis
2:10 - 3:00
RH 222

Brad Currey

Explicit Examples of Wavelet-type Homogeneous Spaces

Thur. Feb 27

Algebra
1:30-2:30
RH 22

Greg Marks

"2-primal rings and the Zariski topology."

Tue. Mar 4

Analysis
2:10 - 3:00
RH 222

Katrina Ashford

TBA

Thur. Mar 6

Algebra
1:30-2:30
RH 22

Dave Jackson

"Uncountability and lengths for basic sequences of commutators.