[Colloquium] TTIC Colloquium: Long Nguyen

[Dawn Ellis]

When:     Tuesday, March 5th @ 3 p.m.

Where:    TTIC, 6045 S. Kenwood Avenue, Room #526

Who:       Long Nguyen,  Department of Statistics, University of Michigan

Abstract:

Admixture models, alternatively known as topic models, are a very
popular tool for modeling and inference in many application areas,
including population genetics, computer vision and text analysis. Of
primary interest is the inference of the latent population structure
(i.e., topic structure in topic models), yet there has been very
little theory explicating its behavior. In this talk I will present
results regarding the posterior contraction behavior of the latent
population structure that arises in admixture models, as the amount of
data increases. A key object of our study is the "population
polytope", which is defined as the convex hull of frequency variables
that define the latent subpopulations or topics. Given suitable
identifiability conditions, rates of convergence are established under
Hausdorff metric and a minimum matching Euclidean metric defined on
the population polytopes, using techniques from convex geometry.
Minimax lower bounds are also established. I will also discuss tools
involved in the development of posterior asymptotics for general
hierarchical models.

Host: Anand Sarwate (asarwate at ttic.edu) and Jinbo Xu (j3xu at ttic.edu).

-- 
Dawn Ellis
Administrative Assistant
773-834-1757
dellis at ttic.edu

TTIC
6045 S. Kenwood Ave.
Chicago, IL. 60637
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