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DTSTART;TZID=America/Los_Angeles:20190204T161500
DTEND;TZID=America/Los_Angeles:20190204T171500
DTSTAMP:20260406T230825
CREATED:20181008T181051Z
LAST-MODIFIED:20190117T015941Z
UID:895-1549296900-1549300500@colleges.claremont.edu
SUMMARY:Estimating the physical location of Twitter users with the von Mises-Fisher distribution (Mike Izbicki\, UC Riverside)
DESCRIPTION:Approximately 500 million tweets are sent everyday.  Scientists monitor these tweets to predict the spread of disease\, better allocate social welfare services\, help first responders during natural disasters\, and many other important tasks.  A key step in each of these tasks is estimating the location the tweet was sent from.  In\nthis talk\, I discuss how to combine machine learning and the von Mises-Fisher distribution to estimate this location.  The von Mises-Fisher distribution is the spherical analog of the Gaussian distribution\, and this distribution lets us exploit the earth’s non-Euclidean geometry to improve estimation accuracy.
URL:https://colleges.claremont.edu/ccms/event/tba-mike-izbicki-uc-riverside/
LOCATION:Emmy Noether Room\, Millikan 1021\, Pomona College\, 610 N. College Ave.\, Claremont\, California\, 91711
CATEGORIES:Applied Math Seminar
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DTSTART;TZID=America/Los_Angeles:20190205T121500
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CREATED:20181205T171033Z
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SUMMARY:Lattices from group frames and vertex transitive graphs (Lenny Fukshansky\, CMC)
DESCRIPTION:Tight frames in Euclidean spaces are widely used convenient generalizations of orthonormal bases. A particularly nice class of such frames is generated as orbits under irreducible actions of finite groups of orthogonal matrices: these are called irreducible group frames. Integer spans of rational irreducible group frames form Euclidean lattices with some very nice geometric properties\, called strongly eutactic lattices. We discuss this construction\, focusing on an especially interesting infinite family in arbitrarily large dimensions\, which comes from vertex transitive graphs. We demonstrate several examples of such lattices from graphs that exhibit some rather fascinating properties. This is joint work with D. Needell\, J. Park and J. Xin.
URL:https://colleges.claremont.edu/ccms/event/antc-talk-lenny-fukshansky-cmc/
LOCATION:Millikan 2099\, Pomona College\, 610 N. College Ave.\, Claremont\, CA\, 91711\, United States
CATEGORIES:Algebra / Number Theory / Combinatorics Seminar
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DTSTART;TZID=America/Los_Angeles:20190206T161500
DTEND;TZID=America/Los_Angeles:20190206T171500
DTSTAMP:20260406T230825
CREATED:20190110T154612Z
LAST-MODIFIED:20190214T061816Z
UID:1002-1549469700-1549473300@colleges.claremont.edu
SUMMARY:Algebraic and Polyhedral Perspectives on Combinatorial Neural Codes (Robert Davis\, Harvey Mudd)
DESCRIPTION:In the 1970s\, James O’Keefe and his team observed that certain neurons in the brain\, called place cells\, spike in their firing rates when the animal is in a particular physical location within its arena. If a place cell is thought of as either “active” or “silent\,” then one may represent the co-firing patterns of place cells by a combinatorial neural code: a set of 0/1 vectors whose coordinates represent that status of distinct place cells. From the code\, we can try to reconstruct a geometric picture of the neural activity by sketching a disjoint union of simple closed curves in the plane. Ideally\, each curve corresponds to a unique place cell and the interiors of the curves are convex. However\, this is not always possible\, and identifying criteria which makes this possible is a difficult problem. \nIn this talk\, we will discuss approaches to the problem of representing combinatorial neural codes using convex sets. We will see how turning the codewords into polynomials can reveal hidden information about the code\, and how this naturally leads to examining properties of related polyhedra. In particular\, we will present progress on using polyhedra to identify representability of a code with circles in the plane.
URL:https://colleges.claremont.edu/ccms/event/ccms-colloquium-robert-davis-harvey-mudd/
LOCATION:Shanahan B460\, Harvey Mudd College\, 301 Platt Blvd.\, Claremont\, CA\, 91711\, United States
CATEGORIES:Colloquium
ORGANIZER;CN="Ali Nadim":MAILTO:ali.nadim@cgu.edu
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