**Seminars and Colloquiums
for 2010-2011
Week of March 28, 2011**

**Speaker:
**Prof. Alexandre Karassev, Nipissing University, Canada, Monday

Professor Jan Rosinski, Monday

Ms. Sarah White, Tuesday

Professor Ohannes Karakashian, Wednesday

Professor Bill Ross, University of Richmond, Wednesday

Mr. Jay Wilkins, Wednesday

Professor Suzanne Lenhart, Thursday

Mr. Matt Turner, Friday

Professor Karen Vogtmann, Cornell, Friday

### If you are interested in giving or arranging a talk for one of our seminars or colloquiums,

### If you are interested in giving or arranging a talk for one of our seminars or colloquiums,

please review our calendar.

If you have questions, or a date you would like to confirm, please contact Dr. Fernando Schwartz.

**Monday, March 28**

TOPOLOGY SEMINAR

TIME: 12:20 p.m. – 1:10 p.m.

ROOM: Ayres Hall 406

SPEAKER: Prof. Alexandre Karassev, Nipissing University, Canada

TITLE: "Spans of continua"

ABSTRACT: The concept of span was introduced by Andrew Lelek in 1964 and played a substantial role in continuum theory since then. Roughly speaking, the span of a space is the largest distance two travellers can keep between them while traversing the whole space. In this talk, we introduce several versions of span and discuss relations between them. Most of the spaces under consideration will be graphs. Some open problems will be posed. This talk is intended to be accessible to graduate students.

PROBABILITY SEMINAR

TIME: 3:35 – 4:25 p.m.

ROOM: Ayres 114

SPEAKER: Professor Jan Rosinski

TITLE: "Identification of semimartingales within infinitely divisible processes"

ABSTRACT: Semimartingales constitute the larges class of "good integrators" for which Ito integral could reasonably be defined and the stochastic analysis machinery applied. In this talk we identify semimartingales within certain infinitely divisible processes. Examples include stationary (but not independent) increment processes, such as fractional and moving average processes, as well as their mixtures. Such processes are non-Markovian, often possess long range memory, and are of interest as stochastic integrators. The talk is based on a joint work with Andreas Basse-O'Connor.

** Tuesday, March 29**

MATH BIOLOGY SEMINAR

TIME: 9:45 – 10:35 p.m.

ROOM: NIMBioS Classroom

SPEAKER: Sarah White

TITLE: "Biological Applications of Continuous Markov Chains", part 2

** Wednesday, March 30**

APPLIED/COMPUTATIONAL MATH SEMINAR

TIME: 3:35 - 4:30 p.m.

ROOM: Ayres 111

SPEAKER: Professor Ohannes Karakashian

TITLE: "Adaptive Methods for Elliptic PDEs", Part VI

ANALYSIS SEMINAR

TIME: 3:35 - 4:25 p.m.

ROOM: Ayres 114

SPEAKER: Professor Bill Ross, University of Richmond

TITLE: "Evangelizing about truncated Toeplitz operators"

ABSTRACT: A few years ago, Don Sarason formalized the topic of truncated Toeplitz operators on model spaces with a beautiful survey paper. Since then several others have taken up this topic. In this talk, I will try to convince the audience that this area has many good results as well as some fascinating open problems.

DOCTORAL DEFENSE

TIME: 4:30 p.m.

ROOM: Ayres 112

SPEAKER: Mr. Jay Wilkins

TOPIC: "Discrete Geometric Homotopy Theory and Critical Values of Metric Spaces"

His committee consists of Professors: Plaut (chair), Conant, Schwartz, and Guidry (Physics).

** Thursday, March 31**

JUNIOR COLLOQUIUM

TIME: 3:35 – 4:25 p.m.

ROOM: Ayres 405

SPEAKER: Professor Suzanne Lenhart

TITLE: "Optimal Harvesting in Fishery Models"

ABSTRACT: We discuss two types of partial differential equation models of fishery harvesting problems. We consider steady state spatial models and diffusive spatial-temporal models. We characterize the distribution of harvest effort which maximizes the harvest yield, and in the steady state
case, also minimizes the cost of the effort. We show numerical results to illustrate various cases. The results inform ongoing debate about the use of reserves (regions where fishing is not allowed), and are increasingly relevant as technology enables enforcement of spatially structured harvest constraints.

Please come for pizza at 3:15.

Friday, April 1

DOCTORAL DEFENSE

TIME: 10:10 a.m.

ROOM: Ayres 405

SPEAKER: Mr. Matt Turner

TITLE: "Explicit Lp-norm estimates of infinitely divisible random vectors in Hilbert spaces with applications"

His committee consists of Professors: Rosinski (chair), Chen, Xiong, and Leitnaker (Statistics).

COLLOQUIUM

TIME: 3:35 – 4:25 p.m.

ROOM: Ayres 405

SPEAKER: Professor Karen Vogtmann, Cornell

TITLE: "Rigidity of automorphism groups of free groups"

ABSTRACT: The contemporary study of mapping class groups and outer automophism
groups of free groups is heavily influenced by the analogy between these groups and lattices in semisimple Lie groups. It can be proved that these groups are not lattices, so the fact that they share many properties with lattices is intriguing and somewhat mysterious. In this talk I will focus on properties of automorphism groups of free groups which echo the strong rigidity properties enjoyed by lattices, i.e. properties which severely restrict the possibilities for homomorphisms between lattices.

Please stop by for refreshments in Ayres 401 at 3:15 p.m.

**Past notices:**

winter break

Seminars from 2009-2010 academic year

Seminars from 2008-2009 academic year

Seminars from 2007-2008 academic year

Seminars from 2006-2007 academic year

Seminars from 2005-2006 academic year