epshteyn (at) math.utah.edu
)January 9. Special Applied Math Seminar.
Speaker: Ricardo Alonso,
Department of Mathematics, PUC-Rio
Title: The 1-D dissipative Boltzmann equation
Abstract: We discuss elementary properties of the 1-D dissipative Boltzmann
equation. In particular, we show the optimal cooling rate of the model, give
existence and uniqueness of measure solutions, and prove the existence of a
non-trivial self-similar profile.
January 13 (Friday). Special Applied Math/Statistics/Stochastics Seminar
Note
Time, 4:15pm - 5:15pm and Place LCB 222.
Speaker:
Dane Taylor,Department of Mathematics, University of North Carolina-Chapel Hill
Title: Optimal layer aggregation and enhanced community detection in
multilayer networks
Abstract: Inspired by real-world networks consisting of layers that encode
different types of connections, such as a social network at different
instances in time, we study community structure in multilayer networks. We
study fundamental limitations on the detectability of communities by
developing random matrix theory for the dominant eigenvectors of matrices
that encode random networks. Specifically, we study modularity matrices
that are associated an aggregation of network layers. Layer aggregation can
be beneficial when the layers are correlated, and it represents a crucial
step for discretizing time-varying networks (whereby time layers are binned
into time windows). We explore two methods for layer aggregation: summing
the layers' adjacency matrices and thresholding this summation at some
value. We identify layer-aggregation strategies that minimize the
detectability limit, indicating good practices (in the context of community
detection) for how to aggregate layers, discretize temporal networks, and
threshold pairwise-interaction data matrices.
January 18 (Wednesday). Special Applied Math/Statistics/Stochastics Seminar.
Note
Time, Wednesday 4pm and Place JWB 335.
Speaker: Wenjing Liao,
Department of Mathematics, Johns Hopkins University
Title: Multiscale adaptive approximations to data and functions near
low-dimensional sets
Abstract: High-dimensional data are often modeled as samples from a probability
measure in $R^D$, for $D$ large. We study data sets exhibiting a low-dimensional
structure, for example, a $d$-dimensional manifold, with $d$ much smaller than
$D$. In this setting, I will present two sets of problems: low-dimensional
geometric approximation to the manifold and regression of a function on the
manifold. In the first case we construct multiscale low-dimensional empirical
approximations to the manifold and give finite-sample performance guarantees. In
the second case we exploit these empirical geometric approximations of the
manifold to construct multiscale approximations to the function. We prove
finite-sample guarantees showing that we attain the same learning rates as if the
function was defined on a Euclidean domain of dimension $d$. In both cases our
approximations can adapt to the regularity of the manifold or the function eve
when this varies at different scales or locations. All algorithms have complexity
$C n\log (n)$ where $n$ is the number of samples, and the constant $C$ is linear
in $D$ and exponential in $d$.
January 30. Special Applied Math Seminar.
Speaker: Michele Coti Zelati,
Department of Mathematics, University of Maryland College Park
Title: Stochastic perturbations of passive scalars and small noise
inviscid limits
Abstract: We consider a class of invariant measures for a passive scalar
driven by an incompressible velocity field on a periodic domain. The
measures are obtained as limits of stochastic viscous perturbations. We
prove that the span of the H1 eigenfunctions of the transport operator
contains the support of these measures, and apply the result to a number
of examples in which explicit computations are possible (relaxation
enhancing, shear, cellular flows). In the case of shear flows, anomalous
scalings can be handled in view of a precise quantification of the
enhanced dissipation effects due to the flow.
February 3 (Friday). Special Applied
Math/Statistics/Stochastics Seminar. Note Time is 3pm - 4pm and Room
is LCB 219.
Speaker: Dan Shen,
Department of Mathematics and Statistics, University of South Florida
Title: PCA Asymptotics & Analysis of Tree Data
Abstract: A general asymptotic framework is developed for studying consistency properties of principal
component analysis (PCA). Our framework includes several previously studied domains of
asymptotics as special cases and allows one to investigate interesting connections and transitions
among the various domains. More importantly, it enables us to investigate asymptotic scenarios
that have not been considered before, and gain new insights into the consistency, subspace
consistency and strong inconsistency regions of PCA and the boundaries among them. In
addition, we studied the asymptotic properties of these sparse PC directions for scenarios with
fixed sample size and increasing dimension (i.e. High Dimension, Low Sample Size (HDLSS)).
Second we develop statistical methods for analyzing tree-structured data objects. This work is
motivated by the statistical challenges of analyzing a set of blood artery trees, which is from a
study of Magnetic Resonance Angiography (MRA) brain images of a set of 98 human subjects.
The non-Euclidean property of tree space makes the application of conventional statistical
analysis, including PCA, to tree data very challenging. We develop an entirely new approach that
uses the Dyck path representation, which builds a bridge between the tree space (a nonEuclidean
space) and curve space (standard Euclidean space). That bridge enables the
exploitation of the power of functional data analysis to explore statistical properties of tree data
sets.
February 24 (Friday). LCB 222, 4:15pm - 5:30pm.
Speaker: Gunilla Kreiss,
Department of Information Technology, Uppsala University
Title: Error analysis for finite difference methods: What is the relation between
the truncation error in a single point, and the global error?
Abstract: In many high order accurate finite difference methods for partial
differential equations cases the local truncation error is significantly larger at a
few points near boundaries than at interior points. The effect can be analyzed by
Laplace transform techniques. In this talk we shall discuss how results from one
space dimension can be extended to higher space dimensions. We will in particular
consider the second order wave equation.
March 6
Speaker: Graeme Milton,
Department of Mathematics, University of Utah
Title: The elasticity tensors of 3d printed materials
Abstract: TBA
March 20
Speaker: Saverio Spagnolie,
Department of Mathematics, University of Wisconsin-Madison
Title: TBA
Abstract: TBA
March 22 (Wednesday).
Note
Time, Wednesday 1pm - 2pm and Place JFB B-1.
Speaker: Nick Trefethen,
Department of Mathematics, University of Oxford
Title: TBA
Abstract: TBA
April 10.
Speaker: Mark Allen,
Department of Mathematics, BYU
Title: TBA
Abstract: TBA
May 15
Speaker: Dmitriy Leykekhman,
Department of Mathematics, University of Connecticut
Title: TBA
Abstract: TBA
epshteyn (at) math.utah.edu
).
Past lectures: Fall 2016, Spring 2016, Fall 2015, Spring 2015, Fall 2014, Spring 2014, Fall 2013, Spring 2013, Fall 2012, Spring 2012, Fall 2011, Spring 2011, Fall 2010, Spring 2010, Fall 2009, Spring 2009, Fall 2008, Spring 2008, Fall 2007, Spring 2007, Fall 2006, Spring 2006, Fall 2005, Spring 2005, Fall 2004, Spring 2004, Fall 2003, Spring 2003, Fall 2002, Spring 2002, Fall 2001, Spring 2001, Fall 2000, Spring 2000, Fall 1999, Spring 1999, Fall 1998, Spring 1998, Winter 1998, Fall 1997, Spring 1997, Winter 1997, Fall 1996, Spring 1996, Winter 1996, Fall 1995.