MathematicsSeminar 
Rocky Mountain Algebraic Combinatorics Seminar
The rigidity of periodic frameworks
Elissa Ross
Worcester Polytechnic Institute, and Mesh Consultants (Fields Institute)
Rigidity theory investigates the flexibility of structures which are defined by geometric constraints (fixed lengths, fixed areas, fixed directions, etc.) on a set of rigid objects (points, lines, planes, polygons, etc.). Since the rigidity properties of a structure  either manmade, such as a building or mechanical linkage, or found in nature, such as a biomolecule, protein or crystal  are critical to its form and function, rigidity theory has many practical applications. One such connection is to materials science. Zeolites are a type of mineral with a repetitive sievelike molecular structure where the "holes" of the sieve expand and contract. Using this as motivation, we study the rigidity properties of infinite periodic frameworks. We think of such a framework as a graph embedded on an ndimensional torus, and we study its rigidity properties through the consideration of its combinatorial, geometric and topological attributes. In this talk we give a general introduction to rigidity theory for both finite and infinite periodic graphs, and outline a selection of related problems and applications.
The Exact Cover Problem in Finite Geometry
Anton Betten
Colorado State University
We will discuss the problem of classifying combinatorial objects, in particular those in finite geometry.
One of the main tools to facilitate this is a reduction to a problem known as "Exact Cover" in computer science. We will see how this fits into a general program to classify combinatorial objects by computer. Plenty of examples illustrating the method will be shared.
Weber 223
4–6 pm
Friday, September 26, 2014
(Refreshments in Weber 117, 3:30–4 pm)
Colorado State University
This is a joint Denver U / UC Boulder / UC Denver / U of Wyoming / CSU seminar that meets biweekly. Anyone interested is welcome to join us at a local restaurant for dinner after the talks.
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