Colloquium SeriesFall 2014Unless otherwise noted, talks will be at 3:50 PM in O'Connor 104. Also, there will be refreshments before each talk in O'Connor 31 at 3:30 PM. Tuesday, Oct 21st Speaker: John Stillwell, University of San Francisco Title: What Does "Depth" Mean in Math? Abstract: Every mathematician believes that certain theorems are "deep," but the concept of depth does not have a formal definition. By looking at some famous theorems, ancient and modern, we will study some candidates for "depth" at various levels, particularly the undergraduate level. With these examples in hand we hope to discuss whether any concepts of logic now available can give "depth" a precise meaning. Tuesday, Oct 28th Speaker: Timothy Hsu, San Jose State Title: Cube complexes, 3manifolds, and the Virtually Fibered Conjecture Abstract: Until recently, the Virtual Haken Conjecture was probably the biggest open problem in 3manifolds (3dimensional geometry). Then, in March 2012, Ian Agol proved a stronger version, known as the Virtually Fibered Conjecture, by completing a key part of Dani Wise's program of studying nonpositively curved cube complexes. So how were questions in 3manifolds resolved using spaces made from highdimensional cubes? We'll give an overview explaining the connection and describe the speaker's joint work with Wise that is part of the emerging and rapidly growing subject of cube complexes. Background: One semester of abstract algebra. No topology required; we will give at least cartoon definitions of the relevant terms from topology (e.g., 3manifold). Tuesday, Nov 11th Speaker: Gregory Smith, Queen's University Title: Nonnegative polynomials and sums of squares Abstract: A polynomial with real coefficients is nonnegative if it takes on only nonnegative values. For example, any sum of squares is obviously nonnegative. For a homogeneous polynomial with respect to the standard grading, Hilbert famously characterized when the converse holds, that is when every nonnegative homogeneous polynomial is a sum of squares. After reviewing some history of this problem, we will examine this converse in more general settings. This line of inquiry has unexpected connections to classical algebraic geometry and leads to new examples in which every nonnegative homogeneous polynomial is a sum of squares. This talk is based on joint work with Grigoriy Blekherman and Mauricio Velasco. Tuesday, Nov 18th Speaker: George Mohler, Santa Clara University Title: The inverse covariance matrix and applications to neural connectivity *** A Pi Mu Epsilon Sponsored Event Abstract: Inferring connectivity of neurons in the brain is an active area of research and has applications to diagnosing neurodegenerative diseases and more generally understanding how connectivity leads to brain function. In this talk we consider the problem of reconstructing unobserved neural connections from Calcium fluorescence time series observations at the neurons. We first will provide an introduction to the inverse covariance matrix, which is a useful tool for determining causality and connectivity in networks. We will then show how inverse covariance can be adapted for neuroimaging data that may be noisy, low resolution, and exhibit synchronized firing. In particular, we will develop a (relatively) simple algorithm with O(10) parameters that achieves stateoftheart reconstruction accuracy compared to more complex models, along with an order of magnitude savings in computational cost. We demonstrate the effectiveness of the algorithm using data from a recent Kaggle competition on neural network reconstruction.
WINTER QUARTER 2015
Tuesday, Jan 20th 2015 Speaker: Rachel Mudge and Nicole Gray, Foothill College Title: How to Communicate with Students in Intentional Ways that Promote Motivation and Persistence
Abstract: Tuesday, TBA Speaker: Bob Kleinhenz, Santa Clara University, Applied Math Dept Title: Counting Atomic Strings with Matrices
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Abstracts of previous talks are available here.
