In many real world applications we have only limited access to networks. For example when we crawl a social network or we design a peer-to-peer system we are restricted to access nodes only locally.

# PACM/Applied Mathematics Colloquium

The PACM Colloquium hosts seminars in the field of applied mathematics. Domains of interest include computational fluid dynamics and material science, dynamical systems, numerical analysis and fast algorithms, stochastic problems and stochastic analysis, graph theory and applications, mathematical biology, financial mathematics and mathematical approaches to signal analysis, image processing and information theory.

For more information about this seminar, contact Amit Singer

**Please click on colloquium title for complete abstract.**

##### Sampling Nodes and Constructing Expanders Locally

Google Research

##### How Far Are We From Having a Satisfactory Theory of Clustering?

Unsupervised learning is widely recognized as one of the most important challenges facing machine learning nowadays. However, unlike supervised learning, our current theoretical understanding of those tasks, and in particular of clustering, is very rudimentary.

University of Waterloo

##### Recent progress in object recognition and symmetry detection in digital images

I will survey developments in the application of invariants of various types, including differential invariant signatures and joint invariant histograms, for object recognition and symmetry detection in digital images. Recent applications, including automated jigsaw puzzle assembly and cancer de

University of Minnesota

##### TBA - Gregory Chikikjian

Johns Hopkins University

##### Physics in the complex plane

The average quantum physicist on the street would say that a quantum-mechanical Hamiltonian must be Dirac Hermitian (invariant under combined matrix transposition and complex conjugation) in order to guarantee that the energy eigenvalues are real and that time evolution is unitary.

Washington University in St. Louis