Mathematics and Statistics Colloquium

The Mathematics and Statistics Colloquium is generally held on Tuesdays from 3:00 to 4:00, with tea at 2:30.

Location: DMTI 111.

Schedule 2019

02/26
Brani Vidakovic, Georgia Insitute of Technology and Emory University 

Abstract: Massive data sets, functional data, and high-frequency sampled processes intrinsically invariant to changes in scale are routinely observed and stored. A catchphrase ``scaling is omnipresent" certainly holds for many high frequency time series and high-resolution images. General multiscale domains provide an environment for analyzing, describing, and modeling data that scale, and for unifying several related attributes describing regularity, fractality, multi-fractality, self-similarity, and long memory.

In this talk we focus on the wavelet-based estimation of scaling indices. In particular, we focus on nondecimated and scale-mixing decompositions. They result in a hierarchy of imbedded multiresolution subspaces that lead to a multiscale spectra. Like in the Fourier transforms, where the rate of linear decay of the log-power spectra over the frequencies characterizes the regularity/smoothness of a time series/image, the slopes in the regression involving the log-averages of squared wavelet coefficients, lead to alternative and arguably more local and stable descriptors of signal/image regularity. Such descriptors, as arguments in ML procedures provide an additional discriminatory power.

An asymptotic distribution for a robust estimator of Hurst exponent based on sample quantiles of log-squared wavelet coefficients is derived. Tukey and Gastwirth trimean based estimators are explored and weights for an optimal trimean estimator are derived as well.

We discuss how the proposed estimators perform in problems coming from medical diagnostics where the scaling indices turn out to be informative in tasks of supervised learning. This work is joint with Chen Feng, speaker's graduate student.

The talk is aimed at non-specialists in wavelets, and a broader scientific audience.

03/12
Spring Break

03/19
Radu Balan, UMD

03/26
Steven Spallone, Indian Institute for Science Education and Research, Pune

Abstract: Given a natural number t and a partition λ, there is a notion of a “remainder of λ upon division by t”, called the t-core of λ. Let s, t be relatively prime, and consider the map taking a given st-core λ to the pair consisting of its s-core and t-core. The fibres of this map are infinite. More precisely, we have proven that the cardinality of the set of length k members of a given fibre is a quasipolynomial in k, of degree st−s−t. This is joint work with K. Seethalakshmi.

04/09
Nimai Mehta, American University 

04/16
Bernard Mair, Howard University

04/23
David Pollack, Wesleyan University

Math and statistics colloquium.

Organizers

Jeff Adler (jadler@american.edu)
Michael Baron (baron@american.edu)

Please email mathstat@american.edu if you would like to be added to the colloquium mailing list.