Rocky Mountain Algebraic Combinatorics Seminar

A formula for Steiner Triple Systems $STS(2^n-1)$ of low 2-rank

Octavio Paez Osuna
Passaic County Community College

In this talk we present a formula for the number of distinct STS(2n−1) of 2-rank ≤ 2nn+1. The formula is obtained using some connections between Steiner Triple Systems and associated codes with certain projective and combinatorial configurations. We show how some combinatorial configurations were enumerated using known STS and how these same configurations may be used to construct and enumerate new STS.


Krein conditions for fun and profit

Sylvia Hobart
University of Wyoming

The Krein conditions for a strongly regular graph (or more generally a distance regular graph) are inequalities based on eigenvalues, giving nonexistence conditions. Starting from basics, I will give three different proofs and discuss a new extension to directed strongly regular graphs.


Weber 223
4–6 pm
Friday, October 31, 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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Previous Seminars:

October 10, 2014
Takunari Miyazaki, Eric Moorhouse
September 26, 2014
Elissa Ross, Anton Betten
September 12, 2014
Petr Vojtěchovský, Alexander Hulpke
May 9, 2014
Philip DeOrsey, Tim Penttila
April 25, 2014
William J Martin, Jason Williford
April 11, 2014
Victor Pambuccian, George Shakan
March 7, 2014
Nathan Lindzey, Jens Harlander
February 21, 2014
Ross McConnell, Anton Betten
November 22, 2013
Justin Hughes, Josh Maglione

Department of Mathematics
Fort Collins, Colorado 80523