The Applied Mathematics and Statistics Colloquium takes place at 3 p.m. on Fridays. The format for the seminars this semester is a 30 minute talk + interview via Zoom.  Please contact Jennifer Ryan at for further information and the Zoom link and password. 

View colloquium videos on YouTube.

Spring 2021

Book Club (See schedule and discussed chapters below):  As part of our colloquia this semester, we will share a discussion of: 

The summary provided from the wikipedia page describes the book in the following manner:
“Rosling suggests the vast majority of human beings are wrong about the state of the world. He demonstrates that his test subjects believe the world is poorer, less healthy, and more dangerous than it actually is, attributing this not to random chance but to misinformation.

Rosling recommends thinking about the world as divided into four levels based on income brackets (rather than the prototypical developed/developing framework) and suggests ten instincts that prevent us from seeing real progress in the world “


January 29Book Club
"Factfulness: 10 Reasons We’re Wrong about the World – and Why Things are Getting Better" (2018), Hans Rosling
Chapters 1-3
February 5Michelle McCarthy
Boston University

Title: Mathematical modeling of neuronal rhythms: from physiology to function

Abstract: Brain rhythms are a ubiquitous feature of brain dynamics, tightly correlated with neuronal activity underlying such basic functions as cognition, emotions, movement, and sleep. Moreover, abnormal rhythmic activity is associated with brain disfunction and altered brain states. Identifying the neuronal units and network structures that create, sustain and modulate brain rhythms is fundamental to identifying both their function and dysfunction in mediating behavioral output. Experimental studies of brain rhythms are limited by the inability to isolate large ensembles of neurons and their interconnections during active brain states. However, mathematical models have been used extensively to study network dynamics of the brain and to give insight into the determinants and functions of brain oscillations during various cognitive and behavioral states. Here I will give a brief introduction to the field of study of rhythmic brain activity and the mathematical formulations underlying biophysical neuronal network models. Existing mathematical models of brain development, sleep and neurodegenerative disease will be used to demonstrate how neuronal models of rhythmic dynamics can be used to explore the link between the brain physiology and functional network dynamics.
February 12Daniel Nordman
Iowa State

Title: Within-sample prediction of a number of future events

Abstract: The talk overviews a prediction problem encountered in reliability engineering, where a need arises to predict the number of future events (e.g., failures) among a cohort of units associated with a time-to-event process. Examples include the prediction of warranty returns or the prediction of the number of future product failures that could cause serious harm. Important decisions, such as a product recall, are often based on such predictions. Data, typically right-censored, are used to estimate the parameters of a time-to-event distribution. This distribution can then be used to predict the number of events over future periods of time. Because all units belong to the same data set, either by providing information (i.e., observed event times) or by becoming the subject of prediction (i.e., censored event times), such predictions are called within-sample predictions and differ from other prediction problems considered in most literature. A standard plug-in (also known as estimative) prediction approach is shown to be invalid for this problem (i.e., for even large amounts of data, the method fails to have correct coverage probability). However, a commonly used prediction calibration method is shown to be asymptotically correct for within-sample predictions, and two alternative predictive-distribution-based methods are presented that perform better than the calibration method.
February 19
Special Time of 1:00 PM
Olivia Prosper
University of Tennessee

Title: Modeling malaria parasite dynamics within the mosquito

Abstract: The malaria parasite Plasmodium falciparum requires a vertebrate host and a female Anopheles mosquito to complete a full life cycle, with sexual reproduction occurring in the mosquito. While parasite dynamics within the vertebrate host, such as humans, has been extensively studied, less is understood about dynamics within the mosquito, a critical component of malaria transmission dynamics. This sexual stage of the parasite life cycle allows for the production of genetically novel parasites. In the meantime, a mosquito’s biology creates bottlenecks in the infecting parasites’ development. We developed a two-stage stochastic model of the generation of parasite diversity within a mosquito and were able to demonstrate the importance of heterogeneity amongst parasite dynamics across a population of mosquitoes on estimates of parasite diversity. A key epidemiological parameter related to the timing of onward transmission from mosquito to vertebrate host is the extrinsic incubation period (EIP). Using simple models of within-mosquito parasite dynamics fitted to empirical data, we investigated factors influencing the EIP.
February 26Book Club
"Factfulness: 10 Reasons We’re Wrong about the World – and Why Things are Getting Better" (2018), Hans Rosling
Chapters 4-6
March 12Lise-Marie Imbert-Gerard
University of Arizona

Title: Wave propagation in inhomogeneous media: An introduction to Generalized Plane Waves

Abstract: Trefftz methods rely, in broad terms, on the idea of approximating solutions to Partial Differential Equation (PDEs) using basis functions which are exact solutions of the PDE, making explicit use of information about the ambient medium. But wave propagation problems in inhomogeneous media is modeled by PDEs with variable coefficients, and in general no exact solutions are available. Generalized Plane Waves (GPWs) are functions that have been introduced, in the case of the Helmholtz equation with variable coefficients, to address this problem: they are not exact solutions to the PDE but are instead constructed locally as high order approximate solutions. We will discuss the origin, the construction, and the properties of GPWs. The construction process introduces a consistency error, requiring a specific analysis.
March 19Ethan Anderes

Title: Gravitational wave and lensing inference from the CMB polarization

Abstract: In the last decade cosmologists have spent a considerable amount of effort mapping the radially-projected large-scale mass distribution in the universe by measuring the distortion it imprints on the CMB. Indeed, all the major surveys of the CMB produce estimated maps of the projected gravitational potential generated by mass density fluctuations over the sky. These maps contain a wealth of cosmological information and, as such, are an important data product of CMB experiments. However, the most profound impact from CMB lensing studies may not come from measuring the lensing effect, per se, but rather from our ability to remove it, a process called delensing. This is due to the fact that lensing, along with emission of millimeter wavelength radiation from the interstellar medium in our own galaxy, are the two dominant sources of foreground contaminants for primordial gravitational wave signals in the CMB polarization. As such delensing, i.e. the process of removing the lensing contaminants, and our ability to either model or remove galactic foreground emission sets the noise floor on upcoming gravitational wave science.

In this talk we will present a complete Bayesian solution for simultaneous inference of lensing, delensing and gravitational wave signals in the CMB polarization as characterized by the tensor-to-scalar ratio r parameter. Our solution relies crucially on a physically motivated re-parameterization of the CMB polarization which is designed specifically, along with the design of the Gibbs Markov chain itself, to result in an efficient Gibbs sampler---in terms of mixing time and the computational cost of each step---of the Bayesian posterior. This re-parameterization also takes advantage of a newly developed lensing algorithm, which we term LenseFlow, that lenses a map by solving a system of ordinary differential equations. This description has conceptual advantages, such as allowing us to give a simple non-perturbative proof that the lensing determinant is equal to unity in the weak-lensing regime. The algorithm itself maintains this property even on pixelized maps, which is crucial for our purposes and unique to LenseFlow as compared to other lensing algorithms we have tested. It also has other useful properties such as that it can be trivially inverted (i.e. delensing) for the same computational cost as the forward operation, and can be used for fast and exact likelihood gradients with respect to the lensing potential. Incidentally, the ODEs for calculating these derivatives are exactly analogous to the backpropagation techniques used in deep neural networks but are derived in this case completely from ODE theory.
March 26Book Club
"Factfulness: 10 Reasons We’re Wrong about the World – and Why Things are Getting Better" (2018), Hans Rosling
Chapters 7-9
April 9Andrew Zammit Mangion
University of Wollongong

Title: Statistical Machine Learning for Spatio-Temporal Forecasting

Abstract: Conventional spatio-temporal statistical models are well-suited for modelling and forecasting using data collected over short time horizons. However, they are generally time-consuming to fit, and often do not realistically encapsulate temporally-varying dynamics. Here, we tackle these two issues by using a deep convolution neural network (CNN) in a hierarchical statistical framework, where the CNN is designed to extract process dynamics from the process' most recent behaviour. Once the CNN is fitted, probabilistic forecasting can be done extremely quickly online using an ensemble Kalman filter with no requirement for repeated parameter estimation. We conduct an experiment where we train the model using 13 years of daily sea-surface temperature data in the North Atlantic Ocean. Forecasts are seen to be accurate and calibrated. We show the versatility of the approach by successfully producing 10-minute nowcasts of weather radar reflectivities in Sydney using the same model that was trained on daily sea-surface temperature data in the North Atlantic Ocean. This is joint work with Christopher Wikle, University of Missouri.
April 16Diogo Bolster
University of Notre Dame

Title: Incomplete mixing in reactive systems - from Lab to Field scale

Abstract: In order for two items to react they must physically come into contact with one another. In the lab we often measure reaction rates by forcing two species to continuously mix together. However, in real systems such forced mixing mechanisms may often not exist and so a natural question arises: How do we take measurements from our well mixed laboratory experiments and use them to make meaningful predictions at scales of interest? In this talk we propose a novel modeling framework that aims precisely to do this. To show its applicability we will discuss it as related to a few examples: (i) mixing driven reactions in a quasi-well-mixed systems (ii) mixing driven reactions in a porous column experiment and (iii) mixing in a highly heterogeneous aquifer with a broad range of velocity and spatial scales.

While this work was originally motivated by chemical reactions in porous media, the modeling framework is much more general than this and should be applicable to a broad range of problems. Also, the term reaction, as defined within our framework, can loosely be defined as an event where two items come together to produce something else; it is not in any way limited to purely chemical reactions.
April 23Kiona Ogle
Northern Arizon
April 30Book Club
"Factfulness: 10 Reasons We’re Wrong about the World – and Why Things are Getting Better" (2018), Hans Rosling
Chapter 9-10 + Factfulness Rules of Thumb

Book Club (See schedule and discussed chapters below):  As part of our colloquia this semester, we will share a discussion of: 

“Weapons of Math Destruction”  by Cathy O’Neil

Zoom link for book club. Please contact Jennifer Ryan at for further information and the Zoom link and password. 

Fall 2020

September 18Zachary J. Grant
Oak Ridge National Lab

Analysis and Development of Strong Stability Preserving Time Stepping Schemes

High order spatial discretizations with monotonicity properties are often desirable for the solution of hyperbolic partial differential equations. These methods can advantageously be coupled with high order strong stability preserving time scheme to accurately evolve solutions forward in time while preserving convex functionals that are satisfied from the design of the spatial discretization. The search for high order strong stability time- stepping methods with large allowable strong stability coefficient has been an active area of research over the last three decades. In this talk I will review the foundations of SSP time stepping schemes as in how to analyze a given scheme, and how to optimally build a method which allows the largest effective stable time step. We will then discuss some extensions of the SSP methods in recent years and some ongoing research problems in the field, and show some the need of the SSP property through simple yet demonstrative examples.
September 25Book Club
“Weapons of Math Destruction”
Chapter 1-4
October 2
October 16Minah Oh
James Madison University

Fourier Finite Element Methods and Multigrid for Axisymmetric H(div) Problems

An axisymmetric problem is a problem defined on a three-dimensional (3D) axisymmetric domain, and it appears in numerous applications. An axisymmetric problem can be reduced to a sequence of two-dimensional (2D) problems by using cylindrical coordinates and a Fourier series decomposition. Fourier Finite Element Methods (Fourier-FEMs) can be used to approximate each Fourier-mode of the solution by using a suitable FEM. Such dimension reduction is an attractive feature considering computation time, but the resulting 2D problems are posed in weighted function spaces where the weight function is the radial component r. Furthermore, the grad, curl, and div operators appearing in these weighted problems are quite different from the standard ones, so the analysis of such weighted problems requires special attention.

Multigrid is an effective iterative method that can be used to solve large matrix systems arising from FEMs. In this talk, I will present a multigrid algorithm that can be applied to weighted H(div) problems that arise after performing a dimension reduction to an axisymmetric H(div) problem. Theoretical results that show the uniform convergence of the multigrid V-cycle with respect to meshsize will be presented as well as numerical results.
October 30Book Club:
“Weapons of Math Destruction”
Chapters 5 - 7
November 6Mokshay Madiman
University of Delaware

Concentration of information for log-concave distributions

In 2011, S. Bobkov and the speaker showed that for a random vector X in R^n drawn from a log-concave density f=e^{-V}, the information content per coordinate, namely V(X)/n, is highly concentrated about its mean. The result demonstrated that high-dimensional log-concave measures are in a sense close to uniform distributions on the annulus between 2 nested convex sets (generalizing the well known fact that the standard Gaussian measure is concentrated on a thin spherical annulus). We present recent work that obtains an optimal concentration bound in this setting, using a much simplified proof. Applications that motivated the development of these results include high-dimensional convex geometry, random matrix theory, and shape-constrained density estimation.

The talk is based on joint works with Sergey Bobkov (University of Minnesota), Matthieu Fradelizi (Université Paris Est), and Liyao Wang.
November 20Ayaboe Edoh
Edwards AFRL

Balancing Numerical Dispersion, Dissipation, and Aliasing for Time-Accurate Simulations

The investigation of unsteady flow phenomena calls for the need to improve time-accurate simulation capabilities. Numerical errors responsible for affecting solution accuracy and robustness can be broadly categorized in terms of dispersion, dissipation, and aliasing. Their presence is a consequence of discretizing the continuous governing equations, and their impact may be felt at all scales (albeit to varying degrees). The task of constructing an effective numerical method may therefore be interpreted in terms of reducing the influence of these errors over as broad a range of scales as possible. Here, a concerted assembly of scheme components is chosen relative to a target aliasing limit. High-order and optimized finite difference stencils are employed in order to achieve accuracy; meanwhile, split representations for nonlinear transport terms are used in order to greatly improve robustness. Finally, tunable and scale-discriminant artificial-dissipation methods are incorporated for de-aliasing purposes and as a means of further enhancing both accuracy and stability. The proposed framework is motivated by the need to devise a numerical format capable of mitigating discretization effects in Large-Eddy Simulations.

December 4Book Club
“Weapons of Math Destruction”
Chapters 8-10
Spring 2020
January 24Mevin Hooten
Colorado State University
Runnning on empty: Recharge dynamics from animal movement data
February 14Mark Risser
Lawrence Berkeley National Laboratory
Bayesian inference for high-dimensional nonstationary Gaussian processes
February 21Donna Calhoun
Boise State University
A fully unsplit wave propagation algorithm for shallow water flows on GPUs
February 28Matthias Katzfuss
Texas A&M
Gaussian-Process Approximations for Big Data
March 20Nancy Rodriguez
April 3Dan Nordman
April 10Grady Wright
April 24 Feng Bao
Fall 2019
August 23Chris Elvidge
NOAA and Mines' Payne Institute of Public Policy
VIIRS Data Gems From the Nights
September 13Cynthia Phillips
Sandia National Laboratory
Advanced Data Structures for National Cyber Security
September 20Will Kleiber
University of Colorado - Boulder
Mixed Graphical-Basis Models for Large Nonstationary and Multivariate Spatial Data Problems
October 4Igor Cialenco
Illinois Institute of Technology
Adaptive Robust Control Under Model Uncertainty
October 18Tathagata Bandyopadhyay
Indian Institute of Management Ahmedabad
Inference Problems in Binary Regression Model with Misclassified Responses
October 25Daniel Forger
University of Michigan
Math, Music and the Mind; Analysis of the performed Trio Sonatas of J.S. Bach
November 8Daniel Larremore
University of Colorado - Boulder
Complex Networks & Malaria: From Evolution to Epidemiology
November 22Marisa Eisenberg
University of Michigan
December 3Russell Cummings
United States Air Force Academy
The DoD High Performance Computing Modernization Program’s Hypersonic Vehicle Simulation Institute: Objectives and Progress
-A Mechanical Engineering Seminar-
Spring 2019
January 25Steve Sain
Jupiter Intelligence
Data Science @ Jupiter
February 1Xingping Sun
Missouri State University
Kernel Based Monte Carlo Approximation Methods
February 8Mandy Hering
Baylor University
Fault Detection and Attribution for a Complex Decentralized Wastewater Treatment Facility
February 22Bailey K. Fosdick
Colorado State University
Inference for Network Regressions with Exchangeable Errors
March 8Radu Cascaval
University of Colorado - Colorado Springs
The Mathematics of (Spatial) Mobility
March 15Amneet Bhalla
San Diego State University
A Robust and Efficient Wave-Structure Interaction Solver for High Density Ratio Multiphase Flows
March 22Robert Lund
Clemson University
Stationary Count Time Series
April 5Hua Wang
Colorado School of Mines
Learning Sparsity-Induced Models for Understanding Imaging Genetics Data
April 26Wen Zhou
Colorado State University
Estimation and Inference of Heteroskedasticity Models with Latent Semiparametric Factors for Multivariate Time Series
May 3Olivier Pinaud
Colorado State University
Time Reversal by Time-dependent Perturbations
Fall 2018
August 31Michael Wakin
Colorado School of Mines
Modal Analysis from Random and Compressed Samples
September 14Michael Scheuerer
National Oceanic and Atmospheric Administration (NOAA)
Generating Calibrated Ensembles of Physically Realistic, High-Resolution Precipitation Forecast Fields based on GEFS Model Output
September 28Kathryn Colborn
CU Denver, Anschutz Medical Campus
Spatio-Temporal Modelling of Malaria Incidence for Early Epidemic Detection in Mozambique
October 12Philippe Naveau
Laboratoire des Sciences du Climat et de l'Environnement, IPSL-CNRS, France
Analysis of Extreme Climate Events by Combining Multivariate Extreme Values Theory and Causality Theory
October 26Carrie Manore
Los Alamos National Laboratory
Modeling Disease Risk with Social and Environmental Drivers and Non-traditional Data Sources
November 2Jon Trevelyan
Durham University, UK
Enriched Simulations in Computational Mechanics
November 9Sarah Olson
Worcester Polytechnic Institute
Modeling Cell Motility: From Agent Based Models to Continuous Approximations
November 30Elwin van't Wout
Pontificia Universidad Católica de Chile
Efficient Numerical Simulations of Wave Propagation Phenomena
December 7Bruce Bugbee
National Renewable Energy Laboratory (NREL)
Spring 2018
March 2Grant Brown
University of Iowa Biostatistics
Working with Approximate Bayesian Computation in Stochastic Compartmental Models
March 9Victoria Booth
University of Michigan Mathematics
Neuromodulation of Neural Network Dynamics
March 23Daniel Appelö
University of Colorado Applied Math
What’s New with the Wave Equation?
April 6Grad Student Showcase
April 20Jem Corcoran
University of Colorado Applied Math
A Birth-and-Death Process for the Discretization of Continuous Attributes in Bayesian Network Structure Recovery
May 4Ian Sloan
University of New South Wales Mathematics
Sparse Approximation and the Cosmic Microwave Background
Fall 2017
August 25Zachary Kilpatrick
University of Colorado Boulder, Department of Applied Mathematics
Evidence accumulation in changing environments: Neurons, organisms, and groups
September 8Lincoln Carr
Colorado School of Mines, Department of Physics
Many-Body Quantum Chaos of Ultracold Atoms in a Quantum Ratchet
September 22Joe Guinness
North Carolina State University, Department of Statistics
A General Framework for Vecchia Approximations of Gaussian Processes
October 13Eliot Fried
Okinawa Institute of Science and Technology, Mathematics, Mechanics, and Materials Unit
Shape Selection Induced by Competition Between Surface and Line Energy
October 20Arthur Sherman
National Institutes of Health
Diabetes Pathogenesis as a Threshold-Crossing Process
November 3Adrianna Gillman
Rice University, Department of Computational and Applied Mathematics
Fast Direct Solvers for Boundary Integral Equations
November 17Laura Miller
University of North Carolina at Chapel Hill, Departments of Mathematics and Biology
Using Computational Fluid Dynamics to Understand the Neuromechanics of Jellyfish Swimming
December 1AMS Graduate Student Showcase
Spring 2017
January 13Roger Ghanem
University of Southern California, Department of Aerospace and Mechanical Engineering
Uncertainty quantification at the interface of computing and everything else
Special joint colloquium with Department of Mechanical Engineering
January 27Wolfgang Bangerth
Colorado State University, Department of Mathematics
Simulating complex flows in the Earth mantle
February 10Chris Mast
Mercer, Actuary and Employee Benefits Consultant
Actuarial problems in employer-sponsored healthcare
February 24Natasha Flyer
National Center for Atmospheric Research, Computational Math Group
Bengt Fornberg
University of Colorado Boulder, Department of Applied Mathematics
Radial basis functions: Freedom from meshes in scientific computing
March 10Michael Sprague
National Renewable Energy Laboratory, Computational Science Center
A computational model for a dilute biomass suspension undergoing mixing and settling
March 24Randall J. LeVeque
University of Washington, Department of Applied Mathematics
Generating random earthquakes for probabilistic hazard assessment
Special joint colloquium with US Geological Survey
April 7Fred J. Hickernell
Illinois Institute of Technology, Department of Applied Mathematics
Think like an applied mathematician and a statistician
April 14Ian Sloan
University of New South Wales, School of Mathematics
How high is high dimensional?
April 21Mark Embree
Virginia Tech, Department of Mathematics
Using interpolatory approximations to learn from an instrumented building
April 28James A. Warren
National Institute of Standards and Technology, Material Measurement Laboratory
The Materials Genome Initiative: NIST, data, and open science
Special joint colloquium with Department of Metallurgical and Materials Engineering
May 5Jessica F. Ellis
Colorado State University, Department of Mathematics
The features of college calculus programs: An overview of the MAA two calculus projects' main findings
Fall 2016
September 2Stephen Becker
University of Colorado Boulder, Department of Applied Mathematics
Subsampling large datasets via random mixing
September 16Art Owen
Stanford University, Department of Statistics
Permutation p-value approximation via generalized Stolarsky invariance
September 30Stefan Wild
Argonne National Laboratory, Mathematics and Computer Science Division
Beyond the black box in derivative-free and simulation-based optimization
October 14Erica Graham
Bryn Mawr College, Department of Mathematics
Modeling physiological and pathological mechanisms in ovulation
October 28Jim Koehler
Google Boulder, Principal Statistician
Statistical methods supporting Google's ad business
November 11Dennis Cook
University of Minnesota, School of Statistics
An Introduction to envelopes: Methods for improving efficiency in multivariate statistics
December 2Howard Elman
University of Maryland, Department of Computer Science
Efficient computational methods for parameterized partial differential equations