Fall 2009
Colloquium Schedule
Department of Mathematics
Fall 2009 Colloquia (and other events) Schedule:
Except as noted, all talks are on Friday, from 4:00 to 4:50pm, in Avery Hall 115, preceded by refreshments at 3:30 pm in Avery Hall 348.
Here is a discussion of what to expect at Colloquium talks and here is a discussion of what might make a good colloquium talk.
Go here for tentative scheduling for colloquia next semester.
Mon Aug 24: First Day of classes
Aug 28: No colloquium
Sep 4: OPEN
Mon Sep 7: Labor Day/no colloq
Sept 11: No colloquium
Sept 18:
Speaker:
Affiliation: Notre Dame
Local host: Roger Wiegand
Title: Blowup Algebras
Abstract: The theory of blowup algebras is a central area of commutative algebra. Blowup algebras are so called because they
are related to the process of blowing up a variety along a subvariety. In this talk we will survey the study of the algebraic
properties of blowup algebras and their ubiquity in commutative algebra. We will close with the long standing open questions
in the subject, such as the implicitization problem.
This colloquium is funded by the UNL Research Council.
Sept.19-20: KUMUNU (Kansas-Missouri-Nebraska Commutative Algebra Conference)
Sep 25: No colloquium
Oct. 2:
Speaker:
Affiliation: Department of Mechanical Engineering, Texas Tech University
Local host: George Avalos
Title: Thermal Properties of Metallic Nanowires: Modeling & Experiment
Abstract: Effects such as surface and grain boundary scattering that are negligible for larger structures significantly influence
electrical and thermal properties of nanoscale objects. These influences have an important practical impact on the performance of
current and next-generation electronic devices. The conventional wisdom for metals holds that thermal transport is predominantly
by electrons, and that contributions due to lattice vibrations---that is, thermal transport by phonons---are negligible. This assumption
is used to justify the use of the Wiedemann-Franz law to infer thermal conductivity based on measurements of electrical resistivity.
Recently, however, experiments have been reported suggesting a breakdown of the Wiedemann-Franz law at the nanoscale.
This talk will revisit the assumption that thermal transport by phonons can be neglected. The electrical resistivities and thermal conductivities
of aluminum nanowires of various sizes are directly measured. These values are used in conjunction with the Boltzmann transport
equation to conclude that the Wiedemann-Franz law describes the electronic component of thermal conductivity, but that the phonon
term must also be considered.
A novel experimental device is described for the direct thermal conductivity measurements. The design is analogous to the Wheatstone
bridge used to measure impedance of electrical components. It is used in conjunction with a complementary least-squares parameter
estimation scheme to reduce sensitivity to modeling errors.
Oct. 9:
Speaker:
Affiliation: Hausdorff Center for Mathematics, Bonn
Local host: Srikanth Iyengar
Title: Duality in singularity categories and string theory
Abstract: Associated to a singular hypersurface is the singularity category, which can be described in terms of matrix factorisations
of the defining equation of the hypersurface. Recently string theorists have used these categories to construct physical models of
''D-branes'', which are extended objects between which the ''open strings'' of the theory are allowed to stretch.
Oct. 16:
Speaker:
Affiliation: UNL
Local host:
Title: Harmonic analysis and geometry in control of partial differential equations
Abstract: Various areas of harmonic analysis and geometry arise in connection with control problems. The talk will provide
examples of how pseudo-differential operators, regularity theory for elliptic equations, differential and algebraic geometry
help determine well-posedness and observability of control systems governed by partial differential equations.
Oct. 19-20: October break/no colloq
Oct. 23: OPEN
Oct. 30:
Speaker: M. Shel Swenson (former UNL undergraduate)
Affiliation: University of Texas, Austin
Local host: Allan Donsig
Title: Phylogenetic Supertree Methods: tools for reconstructing the Tree of Life
Abstract: Estimating the Tree of Life, an evolutionary tree describing how all life evolved from a common ancestor, is one
of the major scientific objectives facing modern biologists. This estimation problem is extremely computationally intensive,
given that the most accurate methods (e.g., maximum likelihood heuristics) are based upon attempts to solve NP-hard
optimization problems. Most computational biologists assume that the only feasible strategy will involve a divide-and-conquer
approach where the large taxon set is divided into subsets, trees are estimated on these subsets, and a supertree method is
applied to assemble a tree on the entire set of taxa from the smaller "source" trees.
I will present supertree methods in a mathematical context, focusing on some theoretical properties of MRP (Matrix Representation
with Parsimony), the most popular supertree method, and SuperFine, a new supertree method that outperforms MRP.
Nov. 6: 3rd Annual Pi Mu Epsilon Lecture
Speaker:
Affiliation: Manchester College, Indiana
Local Hosts: Stephen Hartke and Petronela Radu
Title: The Amazing "Hilda Function"
Abstract: Count the number of base 2 representations of a natural number, allowing digits 0, 1, and 2. This sequence has the
surprising property that every positive rational occurs exactly once as a ratio of consecutive terms. The bijection between
integers and rationals is explained using the Euclidean algorithm and continued fraction expansions.Flipping the bijection
"across the decimal point" leads to an amazing continuous function with wonderful set-theoretic, analytic, and fractal
properties, first discovered by Minkowski.
Nov. 13:
Speaker: Henning Krause
Affiliation: University of Paderborn, Germany
Local hosts: Srikanth Iyengar and Lucho Avramov
Title: TBA
Abstract: Later.
Nov. 20:
Speaker: Stephen Pankavich
Affiliation: University of Texas Arlington
Local host: Petronela Radu
Title: TBA
Abstract: Later.
Dec. 4:
Speaker: Mikil Foss
Affiliation: UNL
Local host:
Title: TBA
Abstract: Later.
Dec. 11: OPEN
Dec. 18: OPEN
Current Schedule of Open Dates for Spring 10
2010:
Rowlee Lecture April 16
Speaker:
Affiliation:University of Chicago
Local Hosts:Mohammad Rammaha and George Avalos
Title:
Abstract:
