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BEGIN:VEVENT
SUMMARY:Victor Barranca (Swarthmore College)
DTSTART:20221129T171500Z
DTEND:20221129T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/1
DESCRIPTION:Title: Reconstruction of Neuronal Network Connectivity and Rival
rous Percepts Via Compressive Sensing of Network Dynamics\nby Victor B
arranca (Swarthmore College) as part of Northwestern Applied Mathematics S
eminar\n\nLecture held in M416 Tech Northwestern Evanston.\n\nAbstract\nNe
uronal network connectivity demonstrates sparsity on multiple spatial scal
es and natural stimuli also possess sparse representations in numerous dom
ains. In this talk\, we underline the role of sparsity in the efficient en
coding of network connectivity and inputs through nonlinear neuronal netwo
rk dynamics. Addressing the fundamental challenge of recovering the struct
ural connectivity of large-scale neuronal networks\, we leverage propertie
s of the balanced dynamical regime and compressive sensing theory to devel
op a theoretical framework for efficiently reconstructing sparse network c
onnections through measurements of the network response to a relatively sm
all ensemble of random stimuli. We further utilize sparse recovery ideas t
o probe the neural correlates of binocular rivalry through dynamic percept
reconstructions based on the activity of a two-layer network model with c
ompeting downstream pools driven by disparate image stimuli. The resultant
model dynamics agree with key experimental observations and give insights
into the excitation/inhibition hypothesis for autism.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Richard Braun (University of Delaware)
DTSTART:20230131T171500Z
DTEND:20230131T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/2
DESCRIPTION:Title: Semi-automated Tear Breakup Detection and Modeling on the
Ocular Surface\nby Richard Braun (University of Delaware) as part of
Northwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech Nort
hwestern Evanston.\n\nAbstract\nThe tear film is a thin fluid multilayer l
eft on the eye surface after a blink. A good tear film is essential for h
ealth and proper function of the eye. Millions of people have a condition
called dry eye disease (DED) that is thought to be closely linked to the
tear film. DED inhibits vision and may lead to inflammation and ocular su
rface damage. However\, there is little quantitative data about tear film
failure\, often called tear break up (TBU). Currently\, it is not possibl
e to directly measure important variables such as tear osmolarity (saltine
ss) within areas of TBU. We present a mostly automatic method that we have
developed to extract data from video of the tear film dyed with fluoresce
in (for visualization). We have extracted data for 15 healthy subjects res
ulting in 467 instances of TBU. Using parameter identification from fits t
o appropriate math models\, we estimate which mechanisms are most importan
t in each instance and determine critical variables such as osmolarity wit
hin regions of TBU. Not only is new data obtained\, but far more data\, en
abling statistical methods to be applied. So far\, the methods provide bas
eline data for TBU in healthy subjects\; future work will produce data fro
m DED subjects.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Keaton Burns (Massachusettes Institute of Technology)
DTSTART:20230207T171500Z
DTEND:20230207T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/3
DESCRIPTION:Title: Solving Partial Differential Equations Exactly Over Polyn
omials\nby Keaton Burns (Massachusettes Institute of Technology) as pa
rt of Northwestern Applied Mathematics Seminar\n\nLecture held in M416 Tec
h Northwestern Evanston.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:David Bortz (University of Colorado Boulder)
DTSTART:20230221T171500Z
DTEND:20230221T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/5
DESCRIPTION:Title: The Surprising Robustness and Computational Efficiency of
Weak Form System Identification\nby David Bortz (University of Colora
do Boulder) as part of Northwestern Applied Mathematics Seminar\n\nLecture
held in M416 Tech Northwestern Evanston.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Daniel Wells (Santa Ana Bio\, Inc.)
DTSTART:20230228T171500Z
DTEND:20230228T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/7
DESCRIPTION:Title: Single Cell Spatial Transcriptomics to Accelerate Systems
Immunology\nby Daniel Wells (Santa Ana Bio\, Inc.) as part of Northwe
stern Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwester
n Evanston.\n\nAbstract\nSingle cell transcriptomics has revolutionized im
munology and driven the emergence of systems-level approaches in immunolog
y. However\, existing technologies work only on dissociated cells and lose
valuable tissue context. Single cell spatial transcriptomics is an emergi
ng field which leverages large scale profiling of RNA and protein in situ
to measure the state of individual cells within intact tissues. Here we wi
ll provide an overview of single cell genomic approaches\, their uses\, an
d demonstrate ways single cell spatial transcriptomics can augment underst
anding of immunology. Particular focus will be paid to emerging analytic a
pproaches to extract differentiated signal from these data. FInally\, we w
ill provide an example of how these approaches can be applied in the setti
ng of autoimmunity.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eva Kanso (University of Southern California)
DTSTART:20230404T161500Z
DTEND:20230404T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/8
DESCRIPTION:by Eva Kanso (University of Southern California) as part of No
rthwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech Northw
estern Evanston IL.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Simone Bianco (Altos Labs - Bay Area Institute of Science)
DTSTART:20230411T161500Z
DTEND:20230411T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/9
DESCRIPTION:by Simone Bianco (Altos Labs - Bay Area Institute of Science)
as part of Northwestern Applied Mathematics Seminar\n\nLecture held in M41
6 Tech Northwestern Evanston IL.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gwynn Elfring (University of British Columbia)
DTSTART:20230418T161500Z
DTEND:20230418T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/10
DESCRIPTION:Title: Active Matter in Inhomogeneous Environments\nby Gwyn
n Elfring (University of British Columbia) as part of Northwestern Applied
Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL
.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Osman Basaran (Purdue University)
DTSTART:20230502T161500Z
DTEND:20230502T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/11
DESCRIPTION:by Osman Basaran (Purdue University) as part of Northwestern A
pplied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evans
ton IL.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sung Ha Kang (Georgia Institute of Technology)
DTSTART:20230509T161500Z
DTEND:20230509T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/12
DESCRIPTION:Title: Identifying Differential Equations with Numerical Method
s: Time Evolution\, Subspace Pursuit and Weak Form\nby Sung Ha Kang (G
eorgia Institute of Technology) as part of Northwestern Applied Mathematic
s Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\nAbstract
: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tiffany Shaw (University of Chicago)
DTSTART:20230516T161500Z
DTEND:20230516T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/13
DESCRIPTION:Title: Fast jet stream winds get faster under climate change\nby Tiffany Shaw (University of Chicago) as part of Northwestern Applied
Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL
.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Linda Petzold (University of California\, Santa Barbara)
DTSTART:20230522T210000Z
DTEND:20230522T221500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/14
DESCRIPTION:Title: The Roles and Consequences of Randomness in Biological S
ystems\nby Linda Petzold (University of California\, Santa Barbara) as
part of Northwestern Applied Mathematics Seminar\n\nLecture held in M416
Tech Northwestern Evanston IL.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Linda Petzold (University of California\, Santa Barbara)
DTSTART:20230523T161500Z
DTEND:20230523T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/15
DESCRIPTION:Title: Interpretable Polynomial Neural ODEs\nby Linda Petzo
ld (University of California\, Santa Barbara) as part of Northwestern Appl
ied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston
IL.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Christine Heitsch (Georgia Institute of Technology)
DTSTART:20231003T161500Z
DTEND:20231003T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/17
DESCRIPTION:Title: How Can Discrete Mathematics Improve RNA Folding Predict
ions\nby Christine Heitsch (Georgia Institute of Technology) as part o
f Northwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech No
rthwestern Evanston IL.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Aleksandra Walczak (ENS\, Paris)
DTSTART:20231010T161500Z
DTEND:20231010T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/18
DESCRIPTION:Title: Mathematics of Life Series: Formation of Immune Repertoi
re\nby Aleksandra Walczak (ENS\, Paris) as part of Northwestern Applie
d Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston I
L.\n\nAbstract\nLink: https://northwestern.zoom.us/j/94392051105\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sam Kriegman (Northwestern University)
DTSTART:20231017T161500Z
DTEND:20231017T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/19
DESCRIPTION:Title: Teaching Evolution Calculus: Efficient Automatic Design
of Robots\nby Sam Kriegman (Northwestern University) as part of Northw
estern Applied Mathematics Seminar\n\nLecture held in M416 Tech Northweste
rn Evanston IL.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/19/
END:VEVENT
BEGIN:VEVENT
SUMMARY:M. Graham (UW Madison)
DTSTART:20231023T210000Z
DTEND:20231023T220000Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/20
DESCRIPTION:Title: Data\, Dynamics\, and Manifolds: Machine Learning Approa
ches for Modeling and Controlling Complex Flows\nby M. Graham (UW Madi
son) as part of Northwestern Applied Mathematics Seminar\n\nLecture held i
n M416 Tech Northwestern Evanston IL.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sky Nicholson (Northwestern University)
DTSTART:20231031T161500Z
DTEND:20231031T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/21
DESCRIPTION:Title: How to Quantify Rare-Events From Microscopic Kinetics Us
ing Tensor Networks\nby Sky Nicholson (Northwestern University) as par
t of Northwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech
Northwestern Evanston IL.\n\nAbstract\nMolecules can undergo reactions an
d diffusion through space\, creating the cornucopia of patterns we observe
in nature. Understanding how these patterns emerge is challenging to stud
y due to the immense separation of scales between the fast microscopic dyn
amics and the macroscopic pattern. A classic example of such a pattern is
bistability\, where a system will spontaneously switch between two macrosc
opic states of the system. Quantifying the rate of switching historically
has relied on waiting for exponentially rare events in the system to be ob
served. Ensembles of such events lead to estimates of kinetic rates. In th
is work we show how to calculate rare macroscopic rates from high-dimensio
nal reaction diffusion systems without resorting to sampling techniques. I
nstead\, we exploit and extract observables such as macroscopic rates by e
volving the ensemble of all possible trajectories. The foundation of this
work is based on using the Doi-Peliti formalism to encode the chemical mas
ter equation into a second-quantized form. This form allows chemical netwo
rks to be readily evolved using efficient tensor network methods. Our resu
lts are illustrated using an adapted version of the bistable Sch¨ogl mode
l with diffusion. We calculate rates over five-orders of magnitude for lar
ge systems (∼ 3 × 1015 microstates) and show strong agreement to kineti
c-Monto Carlo simulations and the more advanced forward flux sampling meth
od. Our Doi-Peliti tensor network procedure demonstrates sub-exponential s
caling in computational expense\, while bypassing complications due to sam
pling errors or needing intimate knowledge of the reaction network as is t
he case with more advanced sampling methods.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Thierry Mora (ENS\, Paris)
DTSTART:20231107T171500Z
DTEND:20231107T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/22
DESCRIPTION:Title: Mathematics of Life Series: Statistical Mechanics of Col
lective Behavior\nby Thierry Mora (ENS\, Paris) as part of Northwester
n Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Ev
anston IL.\n\nAbstract\nSome animal groups behave in a highly coordinated
way\, reminiscent of ordered phases in physics. However\, animals are also
heterogeneous\, have memory\, and operate out of equilibrium. I will pres
ent recent attempts at modeling the complex dynamics of social groups of m
ice interacting freely in a controlled environment. I will then assess how
far from equilibrium collective behaviour might be\, both in recordings o
f real bird flocks and in flocking models.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Milo Lin (UT Southwestern)
DTSTART:20231128T171500Z
DTEND:20231128T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/23
DESCRIPTION:Title: Mathematics of Life Seminar Series: Thermodynamic Limits
of Molecular Computation\nby Milo Lin (UT Southwestern) as part of No
rthwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech Northw
estern Evanston IL.\n\nAbstract\nLiving systems update their status by alt
ering the probability distribution of stochastically rearranging molecules
in response to a change in the system parameters. These updates constitut
e molecular computational steps. Due to the presence of thermodynamic driv
ing forces\, typically in the form of chemical gradients\, these computati
ons convert a molecular system from one non-equilibrium steady state to an
other. Because such steady states are energetically costly to maintain\, t
he question arises as to why nature has evolved this computational scheme.
I will discuss a thermodynamic limit on computation. Namely\, for any mol
ecular system performing any computational step\, the maximum information
gained in the computation is shown to be a simple function of the thermody
namic force. Therefore\, the presence of thermodynamic forces\, and the ex
penditure of energy\, allows biomolecular systems to convert modest change
s in input into striking changes in output that would be surprising or imp
ossible at equilibrium.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Niall Mangan and Katelyn Leisman (Northwestern University)
DTSTART:20231114T171500Z
DTEND:20231114T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/24
DESCRIPTION:Title: Flushed with Insights: The Promising Potential of Poop-B
ased Testing for Public Health\nby Niall Mangan and Katelyn Leisman (N
orthwestern University) as part of Northwestern Applied Mathematics Semina
r\n\nLecture held in M416 Tech Northwestern Evanston IL.\n\nAbstract\nEsti
mating the prevalence of infectious disease in a community is useful for p
ublic health resource allocation\, policy making\, and messaging. When dis
eases such as COVID-19 become endemic in the community it is essential to
have passive indicators that do not depend on voluntary testing data. Our
team is working with public health departments to use wastewater to inform
our understanding of COVID-19 prevalence in communities throughout Illino
is. We have developed a generalized methodology to improve the predictive
power of wastewater from treatment plants in the Chicago area. Connecting
measured SARS-CoV-2 RNA to community prevalence is challenging\, due to ch
anges in the contributing population\, the variable rate of wastewater flo
w\, and the complexity of wastewater media\, which impacts RNA decay rates
and lab measurement accuracy. To quantify the impact of these factors we
also track other viruses including pepper mild mottle virus (PMMoV)\, a bi
omarker for the number of people contributing to the wastewater\, and bovi
ne coronavirus (BCoV)\, a lab process recovery control. We build and compa
re a set of multi-linear regression models\, which incorporate PMMoV\, BCo
V\, and flow rate into a corrected estimate for SARS-CoV-2 RNA concentrati
on. Laboratory methods evolved rapidly during the COVID-19 pandemic\, and
we show that correction terms differ depending on the laboratory procedure
s used in analyzing the samples. Nonetheless\, in all cases a statistical
correction model provides a significant improvement in terms of correlatio
n with hospitalizations and trend analysis over doing no correction.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/24/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Albane Thery (University of Pennsylvania)
DTSTART:20240123T171500Z
DTEND:20240123T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/26
DESCRIPTION:Title: Building Models For Swimmers in Complex and Confined Env
ironments\nby Albane Thery (University of Pennsylvania) as part of Nor
thwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwe
stern Evanston IL.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yue Yu (Lehigh University)
DTSTART:20240206T171500Z
DTEND:20240206T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/27
DESCRIPTION:Title: Nonlocal Operator is All You Need\nby Yue Yu (Lehigh
University) as part of Northwestern Applied Mathematics Seminar\n\nLectur
e held in M416 Tech Northwestern Evanston IL.\n\nAbstract\nDuring the last
20 years there has been a lot of progress in applying neural networks (NN
s) to many machine learning tasks. However\, their employment in scientifi
c machine learning with the purpose of learning physics of complex system
is less explored. Differs from the other machine learning tasks such as th
e computer vision and natural language processing problems where a large a
mount of unstructured data are available\, physics-based machine learning
tasks often feature scarce and structured measurements. \nIn this talk
\, we will take the learning of heterogeneous material responses as an exe
mplar problem\, to investigate the design of neural networks for physics-b
ased machine learning. In particular\, we propose to parameterize the mapp
ing between loading conditions and the corresponding system responses in t
he form of nonlocal neural operators\, and infer the neural network parame
ters from high-fidelity simulation or experimental measurements. As such\,
the model is built as mappings between infinite-dimensional function spac
es\, and the learnt network parameters are resolution-agnostic: no further
modification or tuning will be required for different resolutions in orde
r to achieve the same level of prediction accuracy. Moreover\, the nonloca
l operator architecture also allows the incorporation of intrinsic mathema
tical and physics knowledge\, which improves the learning efficacy and rob
ustness from scarce measurements. \nTo demonstrate the applicability o
f our nonlocal operator learning framework\, three typical scenarios in ph
ysics-based machine learning will be discussed: the learning of a material
-specific constitutive law\, the learning of an efficient PDE solution ope
rator\, and the development of a foundational constitutive law across mult
iple materials. As an application\, we learn material models directly from
digital image correlation (DIC) displacement tracking measurements on a p
orcine tricuspid valve leaflet tissue\, and show that the learnt model sub
stantially outperforms conventional constitutive models.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/27/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Geoff Vallis (Exeter)
DTSTART:20240213T171500Z
DTEND:20240213T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/28
DESCRIPTION:Title: Rainy-Bénard Convection: An Idealization of a Moist Atm
osphere\nby Geoff Vallis (Exeter) as part of Northwestern Applied Math
ematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\n\n
Abstract\nRayleigh-Benard convection is commonly regarded as the benchmark
system for convection in a wide variety of settings\, and its simplicity
has led to a great many theoretical\, experimental and computational studi
es. However\, it is often regarded as irrelevant as a model for convection
in Earth’s atmosphere because of the significant\, almost dominating\,
influence of moisture in the latter system\, in addition to many other com
plications. In an attempt to partially bridge the evident gap between thes
e systems we add a condensate to the Rayleigh-Benard system but keep other
aspects the same. The resulting ‘Rainy-Benard’ system has very rich b
ehavior and in this talk I’ll describe some that behavior and other prop
erties of the system.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/28/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sid Goyal (University of Toronto)
DTSTART:20240220T171500Z
DTEND:20240220T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/29
DESCRIPTION:Title: POSTPONED Mathematics of Life Seminar Series: Competitio
n Across Scales in Biology\nby Sid Goyal (University of Toronto) as pa
rt of Northwestern Applied Mathematics Seminar\n\nLecture held in M416 Tec
h Northwestern Evanston IL.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/29/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Snezhana Abarzhi (U Western Adelaide (Australia))
DTSTART:20240227T171500Z
DTEND:20240227T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/30
DESCRIPTION:Title: Interface Dynamics in Ideal and Realistic Fluids\nby
Snezhana Abarzhi (U Western Adelaide (Australia)) as part of Northwestern
Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Eva
nston IL.\n\nAbstract\nInterface and mixing and their non-equilibrium kine
tics and dynamics couple micro to macro scales\, and are ubiquitous to occ
ur in fluids\, plasmas and materials. Stellar evolution\, plasma fusion\,
reactive fluids\, microfluidics\, purification of water\, and nanofabricat
ion are a few examples of many processes to which dynamics of interfaces i
s directly relevant. This talk presents the rigorous theory of the stabili
ty of the interface – a phase boundary broadly defined. We directly link
the structure of macroscopic flow fields to microscopic interfacial trans
port\, quantify the contributions of macro and micro stabilization mechani
sms to interface stability\, and discover the fluid instabilities never pr
eviously discussed. In ideal and realistic fluids\, the interface stabilit
y is set primarily by the interplay of the macroscopic inertial mechanism
balancing the destabilizing acceleration\, whereas microscopic thermodynam
ics create vortical fields in the bulk. By linking micro to macro scales\,
the interface is the place where balances are achieved.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/30/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Peko Hosoi (Massachusetts Institute of Technology (MIT))
DTSTART:20240326T161500Z
DTEND:20240326T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/31
DESCRIPTION:Title: Filtration and Fluid Mechanics Inspired by the Manta Ray
- Reiss Lecture\nby Peko Hosoi (Massachusetts Institute of Technology
(MIT)) as part of Northwestern Applied Mathematics Seminar\n\nLecture hel
d in M416 Tech Northwestern Evanston IL.\n\nAbstract\nHVAC systems account
for about 20% of U.S. energy consumption of which at least 7% is consumed
by fans. Their energy efficiency strongly depends on their filters: reduc
ing resistance can result in significant energy savings. We explore novel
strategies for filtration inspired by the manta ray\, which has evolved a
system for filtering zooplankton that appears to be unlike any industrial
filtration mechanism. Instead of a sieve strategy\, the manta deploys micr
ostructures\, which are hypothesized to instigate eddies that push particl
es away from the filtration pores\, resisting clogging\, and enabling the
filtration of particles much smaller than the pore size. Using perturbatio
n theory and asymptotics we examine two toy problems that mimic various fe
atures of the filtration strategies employed by manta rays and find that e
xperimental data from wavy channels are consistent with our asymptotic pre
dictions.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/31/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Efi Efrati (Weizmann Institute of Science)
DTSTART:20240416T161500Z
DTEND:20240416T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/32
DESCRIPTION:Title: Frustrated Assemblies: Describing Matter from Within
\nby Efi Efrati (Weizmann Institute of Science) as part of Northwestern Ap
plied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evanst
on IL.\n\nAbstract\nFrustrated assemblies are comprised of ill-fitting bui
lding blocks whose favored local relative arrangement cannot be globally r
ealized. In fact\, most self assembled structures contain some degree of f
rustration. In some cases\, the frustration is locally resolved and leads
to little or no structural consequence\, while in other cases it dominates
the assembly's size\, shape\, and response properties. In this talk\,
I will present different manifestations of geometric frustration as they
naturally arise in molecular crystals\, liquid crystals\, spin systems\, a
nd nanoparticle assemblies. To theoretically study these assemblies we res
ort to an intrinsic approach in which matter is described only through loc
al properties available to an observer residing within the material. The f
rustration is then quantified by the geometric compatibility conditions wh
ose structure allows us to classify the frustration and predict the assemb
ly's behavior without explicitly solving for the ground state of the syste
m.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/32/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ehud Yariv (Technion - Israel Institute of Technology)
DTSTART:20240430T161500Z
DTEND:20240430T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/33
DESCRIPTION:Title: Shocks and Caps in Drop Electrohydrodynamics\nby Ehu
d Yariv (Technion - Israel Institute of Technology) as part of Northwester
n Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Ev
anston IL.\n\nAbstract\nThe problem of electrohydrodynamic drop deformatio
n is well understood in the case where the external electric field is weak
. In one of his many celebrated papers (Proc. R. Soc. A\, 291 1425 159-166
\, 1966)\, G. I. Taylor worked out a complete theory in this limit\, inclu
ding analytical expressions for the electrohydrodynamic flow engendered wi
thin and outside of the drop by the electric field acting on its own induc
ed interfacial charge\, and a simple function of the permittivity\, conduc
tivity and viscosity drop-to-background ratios discriminating between prol
ate or oblate deformation. In this talk\, we will employ numerical a
nd asymptotic tools to explore the effects of interfacial-charge convectio
n\, which were neglected by Taylor but become important at strong electric
fields. In particular\, we will analyze (in 2D\, for simplicity) how Tayl
or’s fore-aft symmetric solution evolves as the electrical Reynolds numb
er is increased from zero to arbitrarily large values. What we shall find
is hinted by the title of the talk. This is joint work with Gunnar G. Peng
\, Rodolfo Brandão and Ory Schnitzer.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/33/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pankaj Mehta (Boston University)
DTSTART:20240507T161500Z
DTEND:20240507T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/34
DESCRIPTION:Title: Mathematics of Life Seminar Series: Randomness\, Complex
ity\, and the Biological Frontier\nby Pankaj Mehta (Boston University)
as part of Northwestern Applied Mathematics Seminar\n\nLecture held in M4
16 Tech Northwestern Evanston IL.\n\nAbstract\nThe towering successes of t
wentieth century theoretical physics were marked by two guiding principles
: symmetry and energy functionals (reflecting equilibrium dynamics). Yet h
ow we can exploit these principles to develop a theory of living systems i
s unclear since the biological world is composed of heterogeneous\, intera
cting components operating out of equilibrium. In this talk\, I will argue
that one possible strategy for taming biological complexity is to embrace
the idea that many biological behaviors we observe are “typical” and
can be modeled using random systems that respect biologically-inspired con
straints. I will focus on showing how this approach can be used to make cl
ose connection with experiments by presenting three vignettes focusing on:
(i) theory-inspired techniques for visualizing single-cell transcriptomic
s data for cellular identity\, (ii) understanding how the interplay betwee
n cross-feeding and competition shapes microbial ecosystems and (iii) the
emergence of chaos in the ecosystems with non-reciprocal interaction.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/34/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Andrew Stuart (California Institute of Technology)
DTSTART:20240521T161500Z
DTEND:20240521T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/35
DESCRIPTION:Title: Operator Learning: Algorithms\, Analysis and Application
s\nby Andrew Stuart (California Institute of Technology) as part of No
rthwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech Northw
estern Evanston IL.\n\nAbstract\nApproximating operators that map between
function spaces can be useful for accelerating systems level tasks in scie
ntific computing\, and for discovering computational models from data. In
its most basic form\, learning an operator may be cast as a form of superv
ised learning in which the input-output pairs are functions. The talk will
overview a variety of specific approximation architectures that have been
developed in the last five years\; emerging theoretical results explainin
g the approximation capabilities of the architectures will be explained\;
and applications to constitutive modeling (plasticity) and inverse problem
s (fluid mechanics) will be given.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/35/
END:VEVENT
BEGIN:VEVENT
SUMMARY:James Fitzgerald (Northwestern University)
DTSTART:20240305T171500Z
DTEND:20240305T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/36
DESCRIPTION:Title: Bridging Theoretical Neuroscience and Neural Data Scienc
e with Simple Models\nby James Fitzgerald (Northwestern University) as
part of Northwestern Applied Mathematics Seminar\n\nLecture held in M416
Tech Northwestern Evanston IL.\n\nAbstract\nNeuroscience is entering a dat
a-rich era that requires computational approaches and opens exciting new p
ossibilities for theory building. Here I will describe how my research gro
up couples neural data science and abstract theoretical modeling to build
interpretable models of diverse neural systems. In my first illustrative e
xample\, I’ll explain our efforts to uncover synaptic plasticity mechani
sms that allow flies to learn probabilistic reward associations and direct
decision making. I’ll then shift to larval zebrafish and whole-brain im
aging to explain how we build and analyze neural network models of sensori
motor processing and behavior.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/36/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Peko Hosoi (Massachusetts Institute of Technology (MIT))
DTSTART:20240327T210000Z
DTEND:20240327T220000Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/37
DESCRIPTION:Title: A Few Short Stories about Probability and Sports - Reiss
Lecture\nby Peko Hosoi (Massachusetts Institute of Technology (MIT))
as part of Northwestern Applied Mathematics Seminar\n\nLecture held in M41
6 Tech Northwestern Evanston IL.\n\nAbstract\nIn most professional sports\
, every physical attribute of an athlete that can be measured is tracked a
nd recorded. There exists an abundance of (relatively) high quality data
— in football\, basketball\, baseball\, cricket\, etc. — which makes s
ports an ideal testing ground for new analyses and algorithms. In this tal
k I will describe a few studies that lie at the intersection of sports and
data. Topics may include: the origin of the increase in home runs in Majo
r League Baseball\; the public health impact of allowing fans in American
football stadiums during the pandemic\; the role of skill and chance in sp
orts and other activities\; measuring “court sense” i.e. an athlete’
s decision-making ability in basketball\; and the design of optimal runnin
g shoes.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/37/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Maciej Lisicki (University of Warsaw and UPenn)
DTSTART:20240409T161500Z
DTEND:20240409T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/38
DESCRIPTION:Title: Tales of tails: Elastohydrodynamics of microscale motion
\nby Maciej Lisicki (University of Warsaw and UPenn) as part of Northw
estern Applied Mathematics Seminar\n\nLecture held in M416 Tech Northweste
rn Evanston IL.\n\nAbstract\nA look into the microworld reveals plethora o
f swimming microorganisms\, which display a rich variety of shapes and swi
mming gaits. Despite this diversity\, physics of microscale imposes univer
sal limitations on their propulsion strategies. In my talk\, I will review
the basic properties of Stokes flows and their consequences on swimming.
Next\, I will show an artificial system of microscale oil droplets that ha
ve the ability to swim due to a surface phase transition driven by environ
mental temperature fluctuations. I will demonstrate how a coarse-grained e
lastohydrodynamic model can be successfully employed to quantitatively des
cribe the motion of droplets. I will also show a couple of other examples
where a simplified elastohydrodynamic model proves useful for the predicti
on of diffusive properties.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/38/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Naomi Oppenheimer (Tel Aviv University\, Israel)
DTSTART:20240312T180000Z
DTEND:20240312T190000Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/39
DESCRIPTION:Title: Hydrodynamic Hamiltonians of Active Two-dimensional Flui
ds\nby Naomi Oppenheimer (Tel Aviv University\, Israel) as part of Nor
thwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwe
stern Evanston IL.\n\nAbstract\nI will describe two biologically inspired
systems that can be analyzed using the same hydrodynamic Hamiltonian forma
lism. The first is ATP synthase proteins\, which rotate in a biological me
mbrane. The second is swimming micro-organisms such as bacteria or algae c
onfined to a two-dimensional film. I will show that in both cases\, the ac
tive systems self-assemble into distinct structural states --- the rotatin
g proteins rearrange into a hexagonal lattice\, whereas the micro-swimmers
evolve into a zig-zag configuration with a particular tilt. While the two
systems differ both on the microscopic\, local interaction\, as well as t
he emerging\, global structure\, their dynamics originate from similar geo
metrical conservation laws applicable to a broad class of fluid flows. I w
ill then show experiments and simulations in which the Hamiltonian is pert
urbed\, leading to different and surprising steady-state configurations.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/39/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tom Dean (Breakthrough Energy)
DTSTART:20240423T161500Z
DTEND:20240423T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/40
DESCRIPTION:Title: Contrail Climate Impacts: Modeling and Mitigation Strate
gies\nby Tom Dean (Breakthrough Energy) as part of Northwestern Applie
d Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston I
L.\n\nAbstract\nAviation accounts for approximately 3.5% of global anthrop
ogenic climate forcing. Of this\, less than half is attributed to the CO2
output from fuel combustion. Nearly half of the total climate impact of av
iation can be attributed to contrail cirrus – cirrus clouds that have be
en seeded by the exhaust plumes of the aircraft – though with considerab
le uncertainty. Given that only around 2-3% of all flights were are likely
responsible for 80% of the global annual contrail climate forcing\, a pot
ential contrail mitigation strategy could involve re-routing this subset o
f flights to minimize the formation of strongly warming contrails. Studies
have shown that such strategies would require as little as 0.2% additiona
l fuel burn. Implementing such a strategy requires an accurate ability to
forecast contrail impacts\, which in turn requires accurate modeling of m
icrophysical atmospheric processes at flight levels. In this talk we will
give an overview of contrail modeling and describe the grid-based Contrail
Cirrus Prediction model (CoCiP)\, whose output is designed to be input as
a layer in flight planning tools.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/40/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rony Granek (Ben Gurion University of the Negev)
DTSTART:20240514T161500Z
DTEND:20240514T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/41
DESCRIPTION:Title: Active Fractal Networks with Stochastic Force Monopoles
and Force Dipoles Unravel Subdiffusion of Chromosomal Loci\nby Rony Gr
anek (Ben Gurion University of the Negev) as part of Northwestern Applied
Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.
\n\nAbstract\nMotivated by the well-known fractal packing of chromatin\, w
e study the Rouse-type dynamics of elastic fractal networks with embedded\
, stochastically driven\, active force monopoles and force dipoles that ar
e temporally correlated. We compute\, analytically – using a general the
oretical framework – and via Langevin dynamics simulations\, the mean sq
uare displacement (MSD) of a network bead. Following a short time superdif
fusive behavior\, force monopoles yield anomalous subdiffusion with an exp
onent identical to that of the thermal system. In contrast\, force dipoles
do not induce subdiffusion\, and the early superdiffusive MSD crosses ove
r to a relatively small\, system-size-independent saturation value. In add
ition\, we find that force dipoles may lead to ``crawling" rotational moti
on of the whole network\, reminiscent of that found for triangular micro-s
wimmers and consistent with general theories of the rotation of deformable
bodies. Moreover\, force dipoles lead to network collapse beyond a critic
al force strength\, which persists with increasing system size\, signifyin
g a true first-order dynamical phase transition. We apply our results to t
he motion of chromosomal loci in bacteria and yeast cells' chromatin\, whe
re anomalous sub-diffusion\, MSD∼ t^ν with ν≃ 0.4\, were found in bo
th normal and ATP-depleted cells\, albeit with different apparent diffusio
n coefficients. We show that the combination of thermal\, monopolar\, and
dipolar forces in chromatin is typically dominated by the active monopolar
and thermal forces\, explaining the observed normal cells vs the ATP-depl
eted cells behavior.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/41/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Krishna Shrinivas (Northwestern University)
DTSTART:20241008T161500Z
DTEND:20241008T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/42
DESCRIPTION:Title: The Many Phases of a Cell\nby Krishna Shrinivas (Nor
thwestern University) as part of Northwestern Applied Mathematics Seminar\
n\nLecture held in M416 Tech Northwestern Evanston IL.\n\nAbstract\nCells
routinely orchestrate reactions\, interactions\, and transport amongst bil
lions of biomolecules in a crowded environment to perform the diverse task
s that underpin life. Rather than occurring in a well-mixed milieu\, biomo
lecules self-organize into dozens of membrane-lacking compartments called
condensates that enable key biological functions and are aberrant in disea
se. I will introduce how phase transitions are emerging as a paradigm unde
rlying condensate assembly and function in cells. During the talk\, I will
describe our efforts that bridge statistical physics\, applied mathematic
s\, and computation to predict emergent multiphase behavior in highly mult
icomponent soft materials and how such materials can be designed to perfor
m information processing or computational tasks.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/42/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Trevor GrandPre (Princeton University)
DTSTART:20241015T161500Z
DTEND:20241015T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/43
DESCRIPTION:Title: Model-free Inference from Time-series Data\nby Trevo
r GrandPre (Princeton University) as part of Northwestern Applied Mathemat
ics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\n\nAbst
ract\nDrawing inferences from experimental data often involves imposing mo
dels\, which can lead to inaccurate conclusions. Theory sometimes points t
o quantities that are significant independent of the underlying mechanisms
\, but making accurate model-free estimates of these quantities can be har
d because finite data generates systematic errors. I present two cases whe
re we develop new methods to address and correct these errors: (1) extract
ing long-term population growth from single-cell lineage data and (2) esti
mating the evidence for the arrow of time in patterns of neural activity.
For population growth\, key observables are the number of divisions and ge
neration times along a lineage for a fixed time. Simple growth rate estima
tors suffer from finite-time bias at short times\; this bias scales invers
ely with time and can be corrected. At longer times\, rare events introduc
e a linearization bias\, causing an abrupt phase transition explained by a
simple model of disordered systems. Our approach yields accurate estimate
s provided the lineage counts and lengths stay below the critical point\,
allowing inference of how mutations and physiological variations impact fi
tness. In the case of neural activity\, the relevant observables are the m
oments of activity and the waiting times between these moments. Estimating
the irreversibility—quantified by the Kullback-Leibler divergence betwe
en the distribution of forward and backward trajectories—faces similar b
iases. Finding the systematic dependence of these biases on sample size al
lows for accurate estimates\, including detecting systems that obey detail
ed balance\, and opens a path to exploring how the brain represents the ar
row of time. Generally\, this new understanding of how model-free estimato
rs rely on a complex order of limits of the amount of data and the length
of each sample may allow quantitative understanding of other relevant proc
esses such as gene regulation\, cell-cycle dynamics\, and signal transduct
ion.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/43/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pedram Hassanzadeh (The University of Chicago)
DTSTART:20241029T161500Z
DTEND:20241029T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/44
DESCRIPTION:Title: Integrating the Spectral Analyses of Neural Networks and
Nonlinear Physics for Explainability\, Generalizability\, and Stability\nby Pedram Hassanzadeh (The University of Chicago) as part of Northwest
ern Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern
Evanston IL.\n\nAbstract\nIn recent years\, there has been substantial int
erest in using deep neural networks (NNs) to improve the modeling and pred
iction of complex\, multiscale\, nonlinear dynamical systems such as turbu
lent flows and Earth’s climate. In idealized settings\, there has been s
ome progress for a wide range of applications from data-driven spatio-temp
oral forecasting to long-term emulation to subgrid-scale modeling. However
\, to make these approaches practical and operational\, i.e.\, scalable to
real-world problems\, a number of major questions and challenges need to
be addressed. These include 1) instabilities and the emergence of unphysic
al behavior\, e.g.\, due to how errors amplify through NNs\, 2) learning i
n the small-data regime\, 3) interpretability based on physics\, and 4) ou
t-of-distribution generalization (e.g.\, extrapolation to different parame
ters\, forcings\, and regimes) which is essential for applications to non-
stationary systems such as a changing climate. While some progress has bee
n made in addressing (1)-(4)\, e.g.\, doing transfer learning for generali
zation\, these approaches have been often ad-hoc\, as currently there is n
o rigorous framework to analyze deep NNs and develop systematic and genera
l solutions to (1)-(4). In this talk\, I will discuss some of the approach
es to address (1)-(4)\, for example\, once we identify spectral bias as th
e cause of instabilities in state-of-the-art weather models like Pangu-wea
ther\, GraphCast\, and FourCastNet. Then I will introduce a new framework
that combines the spectral (Fourier) analyses of NNs and nonlinear physics
\, and leverages recent advances in theory and applications of deep learni
ng\, to move toward rigorous analysis of deep NNs for applications involvi
ng dynamical systems. For example\, this approach can guide and explain tr
ansfer learning and pruning in such applications. I will use examples from
turbulence modeling and weather/climate prediction to discuss these metho
ds and ideas.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/44/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Miranda Holmes-Cerfon (The University of British Columbia)
DTSTART:20241105T171500Z
DTEND:20241105T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/45
DESCRIPTION:Title: The Dynamics of Particles with Ligand-receptor Contacts<
/a>\nby Miranda Holmes-Cerfon (The University of British Columbia) as part
of Northwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech
Northwestern Evanston IL.\n\nAbstract\nOne way to glue objects together at
the nanoscale or microscale is by ligand-receptor interactions\, where sh
ort sticky hair-like ligands stick to receptors on another surface\, much
like velcro on the nanoscale. Such interactions are common in biological s
ystems\, such as white blood cells\, virus particles\, cargo in the nuclea
r pore complex\, etc\, and they are also useful in materials science\, whe
re coating colloids with single-stranded DNA creates particles with progra
mmable interactions. In these systems\, the ligand-receptor interactions n
ot only hold particles together\, but also influence their dynamics. How d
o such particles move? Do they “roll” on each others’ surfaces\, as
is commonly thought? Or could they slide? And does it matter? In this talk
I will introduce our modelling and experimental efforts aimed at understa
nding the coarse-grained dynamics of particles with ligand-receptor intera
ctions. Our models predict these interactions can change the particles' ef
fective diffusion by orders of magnitude. Our experiments\, using DNA-coat
ed colloids\, verify this dramatic dynamical slowdown\, but also show othe
r dynamical features not yet captured by our models\, which suggest new av
enues for exploration.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/45/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mariela Petkova (Harvard University)
DTSTART:20241112T171500Z
DTEND:20241112T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/46
DESCRIPTION:Title: Carving Circuits from Correlative Connectomics\nby M
ariela Petkova (Harvard University) as part of Northwestern Applied Mathem
atics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\n\nAb
stract\nTracing the wiring diagram of a neural circuit is a powerful appro
ach to test\ncomputational models of brain function. Connectomics – the
mapping of\nneurons and their connections in the brain – poses formidabl
e technical and\nconceptual challenges. The former entails the acquisition
and reduction of\nvast amounts of electron microscopy image data to conne
ctivity matrices\,\nachieved through multi-year\, multi-team collaborative
efforts. The latter\nchallenge is the problem of coarse-graining the conn
ectivity matrices to\nneural circuits which exhibit neural activity and fu
nction. I will describe both\nchallenges in the context of mapping the ner
vous system of a small\nvertebrate – the larval zebrafish. In the same a
nimal\, we pair electron\nmicroscopy with functional information from ligh
t microscopy to interrogate\nneural circuit models for animal behavior fro
m sensory inputs to motor output.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/46/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ertugrul Ozbudak (Northwestern University)
DTSTART:20241119T171500Z
DTEND:20241119T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/47
DESCRIPTION:Title: Reengineering Somite Segmentation without the Vertebrate
Segmentation Clock\nby Ertugrul Ozbudak (Northwestern University) as
part of Northwestern Applied Mathematics Seminar\n\nLecture held in M416 T
ech Northwestern Evanston IL.\n\nAbstract\nSomitogenesis establishes the s
egmental pattern of the vertebral column. A molecular segmentation clock s
ets the pace of somite formation while a spatial gradient of ERK activity
instructs segment boundary positions. However\, how cells are primed to fo
rm a segment boundary at discrete locations and how the clock and gradient
are mechanistically integrated were unclear. We developed transgenic repo
rters for the segmentation clock and the gradient in zebrafish embryos. We
show that the segmentation clock periodically inhibits the gradient\, the
refore projecting its oscillation onto the gradient. Pulsatile inhibition
of the gradient can fully substitute for the role of the clock\, and other
targets of the clock are dispensable for sequential segmentation. We prop
ose a “Clock-dependent Oscillatory Gradient (COG)” model in which the
clock periodically triggers discrete jumps of the positional information.
Computational simulations of the COG model explain all experimental observ
ations\; the new model effectively replaces a long-standing textbook model
.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/47/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Evelyn Tang (Rice University)
DTSTART:20241203T171500Z
DTEND:20241203T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/48
DESCRIPTION:Title: Robust Dynamics and Function in Stochastic Topological S
ystems\nby Evelyn Tang (Rice University) as part of Northwestern Appli
ed Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston
IL.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/48/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Luis Amaral (Northwestern University)
DTSTART:20250114T171500Z
DTEND:20250114T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/49
DESCRIPTION:Title: Science Is an All-You-Can-Eat Buffet and I Am Not Dietin
g\nby Luis Amaral (Northwestern University) as part of Northwestern Ap
plied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evanst
on IL.\n\nAbstract\nIn the old days\, mathematicians were alchemists\, ast
ronomers\, astrologers\, chemists\, demographers\, philosophers\, surveyor
s\, and so many other things. Even as recently as 1944\, Schrödinger cou
ld write about “how can the events in space and time which take place wi
thin the spatial boundary of a living organism be accounted for by physics
and chemistry?" In modern times\, it seems that if you do not stick with
your discipline's scope then you are at risk of being dismissed as an int
erloper or a hack. But beauty can be found in many different areas of kno
wledge and rigor can be used to address phenomena from areas lacking rigor
ous abstractions. I will indulge in describing some examples from my lab
’s recent research.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/49/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pedro Saenz (University of North Carolina at Chapel Hill)
DTSTART:20250204T171500Z
DTEND:20250204T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/51
DESCRIPTION:Title: Walking Droplets & Galloping Bubbles\nby Pedro Saenz
(University of North Carolina at Chapel Hill) as part of Northwestern App
lied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evansto
n IL.\n\nAbstract\n"Blending experiments\, simulations and theory\, we wil
l discuss two different problems that are moti-vated by fundamental quest
ions in physics and engineering.\nIn the first part\, we present a classi
cal wave-particle analog of Anderson localization using walking droplets\,
or “walkers\,” which self-propel across a vibrating fluid bath via a
resonant interaction with their guiding wave field. These droplets push
the boundaries of classical mechanics by exhibiting behaviors previously t
hought to be exclusive to the quantum realm. Investigating the erratic mot
ion of walkers over submerged random topographies\, we demonstrate the eme
rgence of localized statistics analogous to those of quantum particles. An
alysis of walker trajectories reveals a suppression of diffusion when the
guiding wave field extends over the disordered topography\, driven by a
wave-mediated resonant coupling that generates an attractive wave potentia
l. This hydrodynamic quantum analog illustrates how a classical particle m
ay localize like a wave. The second part introduces a new symmetry-breakin
g mechanism that enables bubbles to “gallop” along horizontal surfaces
in a vertically vibrated fluid chamber\, propelled by coupling between s
hape oscillation modes. These active bubbles exhibit diverse trajectory re
gimes – rectilinear\, orbital\, and run-and-tumble – tunable by extern
al forcing. By leveraging periodic body deformations and inertial forces\,
galloping bubbles achieve self-propulsion without external forcing in the
ir direction of motion. Proof-of-concept demonstrations illustrate the pot
ential of galloping locomotion for bubble manipulation\, transport and sor
ting\, navigation through complex fluid networks\, and surface cleaning."
\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/51/
END:VEVENT
BEGIN:VEVENT
SUMMARY:James Stone (Institute for Advanced Study)
DTSTART:20250225T171500Z
DTEND:20250225T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/52
DESCRIPTION:Title: Astrophysical Fluid Dynamics at Exascale\nby James S
tone (Institute for Advanced Study) as part of Northwestern Applied Mathem
atics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\nAbst
ract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/52/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Vaseem Shaik (Northwestern University)
DTSTART:20250311T161500Z
DTEND:20250311T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/53
DESCRIPTION:Title: Active Particles in Inhomogeneous Environments\nby V
aseem Shaik (Northwestern University) as part of Northwestern Applied Math
ematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\n\n
Abstract\n"Active particles are living or non-living entities that convert
stored energy to directed motion\, and a suspension of these particles is
termed active matter. Examples of active particles include nanorobots\, m
icroorganisms\, birds\, fish\, and humans. These particles often navigate
through inhomogeneous environments such as gradients in heat\, light\, nut
rients\, fluid viscosity\, or density. They typically respond to these inh
omogeneities by displaying directed motion up or down the gradients\, know
n as taxis. Some well-known types of taxis are chemotaxis in chemical/nutr
ient gradients\, phototaxis in light gradients\, and gravitaxis in gravita
tional field.\n\nHere I focus on the μm - mm sized particles swimming in
the inhomogeneities in mechanical properties of fluid like fluid viscosity
\, density or elasticity gradients. I discuss the recently understood taxi
s in viscosity gradients (viscotaxis). I also talk about how these particl
es behave as light when interacting with sharp viscosity gradients\, and h
ow this behavior can be described by a Snell's like law. Additionally\, I
address taxis in elasticity or relaxation time gradients (durotaxis). I t
hen discuss a new taxis in density gradients (densitaxis)\, that possibly
aids/hinders the diel vertical migration of planktonic organisms in oceans
. I also talk about the mixing by these particles and different ways to qu
antify it. Lastly\, I discuss the effect of noise and how the aforesaid in
homogeneities could be used to control active matter under confinements."\
n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/53/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Brennan Sprinkle (Colorado School of Mines)
DTSTART:20250408T161500Z
DTEND:20250408T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/54
DESCRIPTION:Title: The Countoscope: Counting Particles to Measure Dynamic P
roperties of Suspensions In and Out of Equilibrium\nby Brennan Sprinkl
e (Colorado School of Mines) as part of Northwestern Applied Mathematics S
eminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\n\nAbstract\
nModern microscopy techniques can image complex\, microscopic systems with
an unprecedented resolution – but methods to analyze these images are m
uch less robust. Available techniques to probe dynamics rely on reconstruc
ting particle trajectories\, which can be difficult or impossible in some
cases\, or some form of video analysis\, which can be unreliable and expen
sive. Inspired by the early work of Smoluchowski we introduce the `Countos
cope’\, a technique that near completely ameliorates these issues by sim
ply counting particle number fluctuations in observation boxes. By varying
properties like the size or aspect ratio of the boxes and taking differen
t measures of correlation between these observation boxes\, we can `zoom
’ in or out to measure individual or collective particle kinetics in bot
h passive and active systems. Using colloidal suspensions as a test case\,
we employ a combination of experiments\, simulations\, and analytical the
ory to support our findings.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/54/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jane Kondev (Brandeis University)
DTSTART:20250128T171500Z
DTEND:20250128T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/55
DESCRIPTION:Title: The Scale-Invariant Cell\nby Jane Kondev (Brandeis U
niversity) as part of Northwestern Applied Mathematics Seminar\n\nLecture
held in M416 Tech Northwestern Evanston IL.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/55/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mark Hoefer (University of Colorado Boulder)
DTSTART:20250304T171500Z
DTEND:20250304T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/56
DESCRIPTION:Title: A Wave Theory of Waves\nby Mark Hoefer (University o
f Colorado Boulder) as part of Northwestern Applied Mathematics Seminar\n\
nLecture held in M416 Tech Northwestern Evanston IL.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/56/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sasha Tchekhovskoy (Northwestern University)
DTSTART:20250211T171500Z
DTEND:20250211T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/57
DESCRIPTION:Title: Simulating Black Hole Feasts\, Burps\, and Fireworks
\nby Sasha Tchekhovskoy (Northwestern University) as part of Northwestern
Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evan
ston IL.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/57/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dan Wilson (University of Tennessee Knoxville)
DTSTART:20250415T161500Z
DTEND:20250415T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/59
DESCRIPTION:Title: Phase-Amplitude-Based Techniques for Control and Analysi
s of Strongly Perturbed Limit Cycle Oscillators\nby Dan Wilson (Univer
sity of Tennessee Knoxville) as part of Northwestern Applied Mathematics S
eminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\n\nAbstract\
nWhile phase-based reduction techniques have a rich history in the analysi
s and control of oscillatory dynamical systems\, the overwhelming majority
of theoretical analysis in this field has been performed in the weakly pe
rturbed limit. Comparatively very little is understood about limit cycle
oscillators in response to strong and/or long-lasting perturbations\, most
ly due to the lack of viable reduction strategies that are valid when cons
idering strong perturbations.\n\nIn this presentation\, I will discuss the
use of isostable coordinates\, which characterize level sets of the slowe
st decaying eigenmodes of the Koopman operator in conjunction with phase-b
ased techniques to yield analytically tractable reduced order models that
are valid in the strongly perturbed regime. Applications involving phase
resetting of circadian rhythms following rapid travel across multiple time
zones illustrate the utility of these new methods in situations where sta
ndard\, phase-only techniques fail. \nI will also discuss related work mot
ivated by experimental and detailed computational studies finding that cou
pled circadian oscillators with decreased levels of synchronization are ab
le to more rapidly adjust to changes in circadian time. Theoretical anal
ysis reveals the dynamics of mean-field coupled oscillators can be conside
red in the context of a supercritical Hopf bifurcation\, ultimately provid
ing an explanation for the fundamental relationship between synchronizatio
n and phase resetting efficiency. In the context of jet-lag recovery stra
tegies\, further analysis reveals that transient desynchronization facilit
ates phase resetting when the relaxation rate of the population limit cycl
e is sufficiently slow relative to the natural frequency of the population
oscillation.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/59/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Todd Murphey (Northwestern University)
DTSTART:20250422T161500Z
DTEND:20250422T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/60
DESCRIPTION:Title: Control for Embodied Learning\nby Todd Murphey (Nort
hwestern University) as part of Northwestern Applied Mathematics Seminar\n
\nLecture held in M416 Tech Northwestern Evanston IL.\n\nAbstract\nEmbodie
d learning systems rely on motion synthesis to enable efficient and flexib
le learning during continuous online deployment. Motion motivated by learn
ing needs can be found throughout natural systems\, yet there is surprisin
gly little known about synthesizing motion to support learning for robotic
systems. Moreover\, robotic systems will need to collect data autonomousl
y for learning\, for instance when isolated for long period of time or whe
n encountering novel environmental features. Learning goals create a disti
nct set of control-oriented challenges\, including how to choose measures
as objectives\, synthesize real-time control based on these objectives\, i
mpose physics-oriented constraints on learning\, and produce analyses that
certify performance and safety with limited knowledge. This talk will dis
cuss learning tasks that robots encounter\, abstractions that enable regul
ating information content of observations\, and recent progress on algorit
hms for generating action plans that facilitate learning.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/60/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chris Vogl (Lawrence Livermore National Laboratory)
DTSTART:20250506T161500Z
DTEND:20250506T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/61
DESCRIPTION:Title: Improving Global Atmosphere Simulation in Earth System M
odels with Multiphysics Time Integration Methods\nby Chris Vogl (Lawre
nce Livermore National Laboratory) as part of Northwestern Applied Mathema
tics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\n\nAbs
tract\nTo reliably predict the frequency and severity of hurricanes\, floo
ds\, droughts\, and other weather-driven disasters\, the efficient simulat
ion of Earth system models is crucial. Such an endeavor poses a complex\,
multiphysics problem involving modeling\, temporal and spatial discretizat
ion\, and software implementation considerations. This work focuses on the
time integration of the global atmosphere component\, with an emphasis on
the bulk atmosphere flow and cloud microphysics models. The nonhydrostati
c bulk atmosphere flow models include acoustic waves that make the overall
system numerically stiff. Our work has developed a model formulation that
is amenable to an IMEX approach\, where the acoustic waves are treated im
plicitly. The performance of both existing and customized additive Runge-K
utta methods is evaluated\, with certain methods remaining stable at the h
ydrostatic timestep. Cloud microphysics models currently use first-order o
perator splitting to address the multiple timescales in the modeled physic
s\, with at-best-first-order limiters required to keep quantities physical
. Our work has shown that higher-order explicit\, implicit\, and IMEX Rung
e-Kutta methods with error-based adaptive timestep control are more effici
ent for the subset of cloud microphysics considered thus far.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/61/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yiping Lu (Northwestern University)
DTSTART:20250527T161500Z
DTEND:20250527T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/62
DESCRIPTION:Title: Two Tales\, One Resolution: Physics-Informed Test Time S
caling and Precondition\nby Yiping Lu (Northwestern University) as par
t of Northwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech
Northwestern Evanston IL.\n\nAbstract\nIn this talk\, I will introduce a
novel framework for physics-informed debiasing of machine learning estimat
ors\, which we call Simulation-Calibrated Scientific Machine Learning (SCa
SML). This approach leverages the structure of physical models to achieve
two key objectives:\n\nUnbiased Predictions: It produces unbiased predicti
ons even when the underlying machine learning predictor is biased.\nOverco
ming Dimensionality Challenges: It mitigates the curse of dimensionality t
hat often affects high-dimensional estimators.\n\nThe SCaSML paradigm inte
grates a (potentially) biased machine learning algorithm with a de-biasing
procedure that is rigorously designed using numerical analysis and stocha
stic simulation. Our methodology aligns with recent advances in inference-
time computation—similar to those seen in the large language model liter
ature—demonstrating that additional computation can enhance ML estimates
.Furthermore\, we establish a surprising equivalence between our framework
and another research direction that utilizes approximate (linearized) sol
vers to precondition iterative methods. This connection not only bridges t
wo distinct areas of study but also offers new insights into improving est
imation accuracy in complex\, high-dimensional (PDE) settings.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/62/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Adrienne Fairhall (Reiss Lecture) (University of Washington)
DTSTART:20250513T161500Z
DTEND:20250513T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/63
DESCRIPTION:Title: Decoding Neurons to Behavior in a Model Organism\nby
Adrienne Fairhall (Reiss Lecture) (University of Washington) as part of N
orthwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech North
western Evanston IL.\n\nAbstract\nThe freshwater cnidarian Hydra is a fasc
inating model organism for neuroscience. It is transparent\; new genetic l
ines allow one to image activity in both neurons and muscle cells\; it exh
ibits a quite rich suite of behaviors\; and it continually rebuilds itself
. Hydra’s fairly simple physical structure as a two-layered fluid-filled
hydrostat and the accessibility of information about neural and muscle ac
tivity open the possibility of a complete model of neural control of behav
ior. We have developed a biophysical and biomechanical model of Hydra's mu
scles and body that allows us to transform measured neural activity into b
ehavior. We also propose a model for how the neural network rebuilds as th
e animal regenerates itself following bisection.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/63/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Johannes Schmidt-Hieber (University of Twente)
DTSTART:20250429T161500Z
DTEND:20250429T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/64
DESCRIPTION:Title: Understanding the Effect of GCN Convolutions in Regressi
on Tasks - NITMB Lecture\nby Johannes Schmidt-Hieber (University of Tw
ente) as part of Northwestern Applied Mathematics Seminar\n\nLecture held
in M416 Tech Northwestern Evanston IL.\n\nAbstract\n"Graph Convolutional N
etworks (GCNs) have become a pivotal method in machine learning for modeli
ng functions over graphs. Despite their widespread success across various
applications\, their statistical properties (e.g. consistency\, convergenc
e rates) remain ill-characterized. To begin addressing this knowledge gap\
, in this paper\, we provide a formal analysis of the impact of convolutio
n operators on regression tasks over homophilic networks. Focusing on esti
mators based solely on neighborhood aggregation\, we examine how two commo
n convolutions - the original GCN and GraphSage convolutions - affect the
learning error as a function of the neighborhood topology and the number o
f convolutional layers. We explicitly characterize the bias-variance trade
-off incurred by GCNs as a function of the neighborhood size and identify
specific graph topologies where convolution operators are less effective.
Our theoretical findings are corroborated by synthetic experiments\, and p
rovide a start to a deeper quantitative understanding of convolutional eff
ects in GCNs for offering rigorous guidelines for practitioners.\n \nJoint
work with Juntong Chen (Twente)\, Claire Donnat (U Chicago)\, and Olga Kl
opp (ESSEC Business School\, Paris)"\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/64/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Adrienne Fairhall (Reiss Lecture) (University of Washington)
DTSTART:20250512T210000Z
DTEND:20250512T220000Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/65
DESCRIPTION:Title: In Search of Internal Mental Models\nby Adrienne Fai
rhall (Reiss Lecture) (University of Washington) as part of Northwestern A
pplied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evans
ton IL.\n\nAbstract\nHow do we build the mental models that we use to perc
eive\, navigate and reason about the world? How might these models be infe
rred from neural activity? I will describe experiments and analysis in col
laboration with Beth Buffalo's lab to explore these questions in our close
st relatives\, nonhuman primates. In one example\, we compare monkey and h
uman behavior in a decision task\, and analyze how subjects make use of vi
sual information and feedback to infer a hidden rule\, where the rule swit
ches in an uncued fashion. We fit a suite of behavioral models and learn t
hat while humans are close to optimal Bayesian agents\, monkey behavior is
better fit as reinforcement learning. This allows us to seek neural imple
mentations of this internal belief update. Further\, while rodent hippocam
pus famously encodes the animal's spatial location\, we find evidence that
hippocampus in the primate serves a more cognitive role.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/65/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Niall Mangan (Northwestern University)
DTSTART:20251002T161500Z
DTEND:20251002T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/66
DESCRIPTION:Title: Data-driven model discovery meets mechanistic modeling f
or dynamical systems\nby Niall Mangan (Northwestern University) as par
t of Northwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech
Northwestern Evanston IL.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/66/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Todd Gingrich (Northwestern University)
DTSTART:20251016T161500Z
DTEND:20251016T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/67
DESCRIPTION:Title: Tensor Networks for Stochastic Chemical Kinetics\nby
Todd Gingrich (Northwestern University) as part of Northwestern Applied M
athematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\
n\nAbstract\nChemical processes exhibit chaotic\, high-dimensional dynamic
s as molecules undergo reactions and diffusion. In the special case of a c
losed\, isolated system\, the complex dynamical processes relax into a com
paratively simple equilibrium steady-state probability distribution. When
the stochastic chemical kinetics describes a nonequilibrium process\, how
can we computationally study the steady state? The traditional answer is t
o sample trajectories. In this talk\, I will discuss how the tensor networ
k techniques (DMRG & TDVP) from quantum many-body problems are naturally r
epurposed to study many-body stochastic chemical kinetics.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/67/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Meridith Joyce (University of Wyoming)
DTSTART:20251023T161500Z
DTEND:20251023T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/68
DESCRIPTION:Title: How to Find a Star by Accident\, or How Not to Solve the
"Great Dimming" of Betelgeuse\nby Meridith Joyce (University of Wyomi
ng) as part of Northwestern Applied Mathematics Seminar\n\nLecture held in
M416 Tech Northwestern Evanston IL.\n\nAbstract\nAlpha Orionis\, popularl
y known as Betelgeuse\, is a nearby red supergiant star visible to the nak
ed eye. In light of the star's "Great Dimming"—a sudden\, extreme drop i
n brightness that occurred in early 2020—a recent controversy surroundin
g Betelgeuse concerned whether it would explode as a supernova within the
next few years\, centuries\, or millennia. Using a series of numerical tec
hniques including one-dimensional stellar evolution models\, hydrodynamic
simulations\, linear oscillation calculations\, Fourier analysis\, and the
methods of a subfield of stellar astrophysics known as asteroseismology\,
my collaborators and I constrained the timeline for Betelgeuse's demise a
nd revised many of the best estimates for its fundamental properties. In d
oing so\, we discovered not only that Betelgeuse was not likely to undergo
an imminent detonation\, but that a pulsation signal unexplained by our m
odels was\, in fact\, the signature of an as-yet-undiscovered binary compa
nion. Its presence was confirmed earlier this year. What we never managed
to do was explain the Great Dimming.\n\nIn this talk\, I will use the stor
y of the discovery of Betelgeuse’s hidden\, low-mass binary companion\,
Alpha Orionis B—affectionately nicknamed “Betelbuddy”—both to high
light the computational and numerical techniques employed in modern stella
r astrophysics and to illustrate how the most meaningful discoveries often
arise not from confirming what we set out to find\, but from venturing do
wn the rabbit holes of unexpected problems that emerge along the way.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/68/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Leonid Berlyand (The Pennsylvania State University)
DTSTART:20251106T171500Z
DTEND:20251106T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/69
DESCRIPTION:Title: Introduction to Mathematics of Artificial Neural Network
s (ANNs)\nby Leonid Berlyand (The Pennsylvania State University) as pa
rt of Northwestern Applied Mathematics Seminar\n\nLecture held in M416 Tec
h Northwestern Evanston IL.\n\nAbstract\nWe begin by addressing the image
classification problem\, where the goal is to map images x to classes α u
sing an exact classifier Φ(x\,α). Since an exact classifier is often unf
easible\, Artificial Neural Networks (ANNs) F(x\,α) are used to approxima
te Φ(x\,α)\, with α representing tunable parameters. Unlike classical m
ethods that use coefficients in expansions\, ANN parameters are inspired b
y the structure of the human brain. The process of optimizing these parame
ters is called training.\n\nWe highlight two advancements: First\, a pruni
ng technique using the Marchenko-Pastur spectral approach from Random Matr
ix Theory (RMT)\, which reduces computational complexity without sacrifici
ng accuracy. Second\, we examine autoencoders\, a special type of ANN used
for image-to-image transformations. The focus is on the fixed points of t
he autoencoder function F(x\,α)\, crucial for distinguishing real images
from fakes. Using the Banach Fixed Point Theorem\, we show that with light
-tailed distributions (e.g. Gaussian)\, there is a unique stable fixed poi
nt\, while with heavy-tailed distributions (e.g. Cauchy)\, there are multi
ple fixed points N. The number of fixed points N depends non-monotonically
on the number of layers L\, suggesting an optimal number of layers L_0 fo
r best performance. These results are vital for improving autoencoder desi
gn.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/69/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nick Moore (Colgate University)
DTSTART:20251113T171500Z
DTEND:20251113T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/70
DESCRIPTION:Title: Reversals of the Large-scale Circulation in Thermal Conv
ection\nby Nick Moore (Colgate University) as part of Northwestern App
lied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evansto
n IL.\n\nAbstract\nThermal convection\, or the tendency of heat to rise an
d cool material to descend\, often gives rise to a large-scale circulatory
flow structure. It is known that the large-scale circulation (LSC) can un
dergo spontaneous reversals. In the atmosphere\, reversals can result in a
sudden change in wind direction\, while in Earth’s liquid core\, revers
als may play a role in magnetic dipole shifts. I will discuss LSC reversal
s in the context of 2D annular thermal convection. Through comparison with
direct numerical simulations\, I’ll show that a low-dimensional dynamic
al system derived systematically from Galerkin truncation of the governing
equations accurately describes a sequence of parameter bifurcations\, inc
luding the onset of circulatory flow\, the appearance of chaotic LSC rever
sals\, and finally a high-Rayleigh-number state of periodic LSC reversals
with small-scale turbulence. When cast in terms of the fluid’s angular m
omentum and center of mass\, the model reveals equivalence to a pendulum s
ystem with driving term that raises the center of mass above the fulcrum.
It is the competition between driving\, restoring\, and damping that leads
to the range of convective states. This physical picture yields accurate
predictions for the frequency of regular LSC reversals in the high Rayleig
h-number limit and offers a transparent mechanism for reversals. I will br
iefly discuss extensions of the model\, including one that accurately reco
vers the gross heat transport.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/70/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ed Lyman (University of Delaware)
DTSTART:20251120T171500Z
DTEND:20251120T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/71
DESCRIPTION:Title: Elastic and Dynamic Response of Membranes Across Scales<
/a>\nby Ed Lyman (University of Delaware) as part of Northwestern Applied
Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.
\n\nAbstract\nCell membranes are quasi-2D soft materials\, about 5 nm thic
k but with hundreds of square microns of surface area. They are a bilayer
structure\, assembled from amphiphilic molecules (lipids) and proteins. Th
e function of membranes imposes challenging design constraints: impermeabl
e yet fluid\, mechanically robust yet deformable. Across the tree of life\
, cells meet these challenges by synthesizing a diverse array of lipids\,
whose chemistry and interactions determine the key continuum properties\,
like stiffness against bending and the viscosity which controls diffusion
and encounter of membrane bound signaling partners. In this talk I will pr
esent our group's work using simulations to connect lipid chemistry and me
mbrane properties\, focusing on two applications. The first project consid
ers the membranes of a family of marine invertebrates called ctenophores\,
which synthesize a specialized lipid chemistry to maintain membrane defor
mability at high pressure. The second project focuses on how lipid chemist
ry is used to control the viscosity of the membrane\, and the challenges t
hat come with trying to measure the viscosity of soft\, thin\, not-quite t
wo dimensional fluids.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/71/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mike Shelley (Flatiron Institute)
DTSTART:20251027T161500Z
DTEND:20251027T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/72
DESCRIPTION:Title: Self-Organization\, Flows\, and Transport in (and of) Li
ving Cells\nby Mike Shelley (Flatiron Institute) as part of Northweste
rn Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern E
vanston IL.\n\nAbstract\nOrganisms organize their internal contents at the
microscale through striking dynamical processes. In the early C. elegans
embryo\, pronuclei are positioned by the interplay of centrosomal arrays a
nd molecular motors as the cell prepares for its first division. In female
Drosophila\, self-organized intracellular flows transport materials acros
s growing egg cells\, establishing functional asymmetries essential for de
velopment. And in males\, ultralong sperm - as long as the organism itself
- are packed and stored in a remarkable state of ordered unrest.\n\nI wil
l describe our work at Flatiron in understanding these phenomena by tightl
y interfacing multiscale modeling and simulation with quantitative experim
ent. The theoretical frameworks draw on fluid and nonlinear dynamics\, coa
rse-graining\, and active matter\, and show how applied mathematics can il
luminate the biophysical mechanisms that enable living systems to build\,
move\, and organize themselves.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/72/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Roberto Zenit (Brown University)
DTSTART:20260212T171500Z
DTEND:20260212T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/73
DESCRIPTION:Title: The Fluid Mechanics of Splatter Painting\nby Roberto
Zenit (Brown University) as part of Northwestern Applied Mathematics Semi
nar\n\nLecture held in M416 Tech Northwestern Evanston IL.\n\nAbstract\nIn
splat painting\, a collection of liquid droplets is projected onto the su
bstrate by imposing a controlled acceleration to a paint-loaded brush.\n\n
To unravel the physical phenomena at play in this artistic technique\, we
perform experiments where the amount of expelled liquid is characterized f
unction of the liquid viscosity\, brush properties and imposed acceleratio
n. Experimental trends are rationalized by simple physical models\, reveal
ing the existence of an inertia-dominated flow in the anisotropic\, porous
tip of the brush. We argue that splat painting artists intuitively tune t
heir technique to work in this regime\, which may also play a role in othe
r pulsed flows\, like fabric drying\, violent expiratory events or sudden
geophysical processes.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/73/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chaoming Song (University of Miami (sabbatical at Northwestern Uni
versity))
DTSTART:20260219T171500Z
DTEND:20260219T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/74
DESCRIPTION:Title: Collective Social Dynamics Through the Lens of Statistic
al Physics\nby Chaoming Song (University of Miami (sabbatical at North
western University)) as part of Northwestern Applied Mathematics Seminar\n
\nLecture held in M416 Tech Northwestern Evanston IL.\n\nAbstract\nSocial
dynamics emerge from the complex interactions among large groups of indivi
duals. Despite their diversity\, many social systems exhibit comparable co
llective behaviors\, ranging from sudden shifts in group states to gradual
diffusion and spreading processes\, analogous to those found in physical
systems. These shared patterns provide unique opportunities to apply the t
ools and principles of statistical physics\, including phase transitions\,
critical phenomena\, self-organization\, and non-equilibrium processes\,
to uncover the fundamental mechanisms driving large-scale social phenomena
. In this talk\, I will present case studies illustrating complex human be
haviors across multiple social systems\, addressing topics such as opinion
polarization\, social unrest\, and the diffusion of scientific innovation
. We conclude with an exploration of social interactions among children in
classroom environments\, revealing an analogy in which coexistence phases
\, similar to those observed in multiphase liquid systems\, can also emerg
e in social contexts.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/74/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Melanie Mitchell (Santa Fe Institute)
DTSTART:20260514T161500Z
DTEND:20260514T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/76
DESCRIPTION:Title: Reiss Lecture\nby Melanie Mitchell (Santa Fe Institu
te) as part of Northwestern Applied Mathematics Seminar\n\nLecture held in
M416 Tech Northwestern Evanston IL.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/76/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ching-Yao Lai (Stanford University)
DTSTART:20260129T171500Z
DTEND:20260129T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/77
DESCRIPTION:by Ching-Yao Lai (Stanford University) as part of Northwestern
Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Eva
nston IL.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/77/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rich Townsend (University of Wisconsin)
DTSTART:20260205T171500Z
DTEND:20260205T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/78
DESCRIPTION:Title: Numerical Asteroseismology with the GYRE Code\nby Ri
ch Townsend (University of Wisconsin) as part of Northwestern Applied Math
ematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\n\n
Abstract\nSome stars display periodic fluctuations in their brightness\, a
rising from the excitation of their global oscillation modes. By modeling
these fluctuations\, we can place remarkably narrow constraints on the sta
rs' global properties and detailed internal structure—a technique known
as "asteroseismology".\n\nIn this talk I'll review the theoretical princip
les of asteroseismology\, and describe their implementation in GYRE—an o
pen-source code I've been developing for a little over a decade. Despite c
ommitting a fair number of computational cardinal sins\, GYRE appears to b
e accurate\, robust\, and fast\, and has been adopted by many groups aroun
d the world as their workhorse for numerical asteroseismology. I'll showca
se a few GYRE-based projects that I've recently been involved in\, and the
n discuss enhancements that enable GYRE to simulate tidal phenomena in bin
ary-star and star-planet systems.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/78/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Stefano Allesina (University of Chicago)
DTSTART:20260226T171500Z
DTEND:20260226T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/79
DESCRIPTION:Title: Global stability of ecological and evolutionary dynamics
via equivalence\nby Stefano Allesina (University of Chicago) as part
of Northwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech N
orthwestern Evanston IL.\n\nAbstract\nThe replicator and the Generalized L
otka-Volterra equations are closely-related\, foundational models in evolu
tionary game theory and community ecology\, respectively. The concept of e
volutionary stability and its relationship with dynamic stability has rece
ived significant attention: in the replicator equation\, a mixed evolution
ary stable strategy is also dynamically globally stable—i.e.\, will be r
eached by any trajectory originating from positive conditions. Intriguingl
y\, the converse is not true: there are replicator equations yielding dyna
mically stable mixed strategies that are not evolutionary stable. Here we
consider two classes of equivalence (i.e.\, transformations that do not al
ter the qualitative dynamics) for the replicator equation\, to determine w
hether a globally-stable\, but not evolutionary stable strategy maps into
an equivalent state that is evolutionary stable—and show that this is th
e case for the examples that have been put forward so far. We derive the s
ame two classes of equivalence for the Generalized Lotka-Volterra model\,
obtaining the same conditions for stability as for the replicator equation
\, and show that in this way we can characterize stability when other meth
ods fail. By unifying the approach to proving stability for the replicator
equation and Lotka-Volterra models\, we bring these foundational equation
s even closer together.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/79/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Xiao Yu Wang (CRI Foundation)
DTSTART:20260312T161500Z
DTEND:20260312T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/80
DESCRIPTION:Title: What the proposed credit card regulation really means fo
r consumers\nby Xiao Yu Wang (CRI Foundation) as part of Northwestern
Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evan
ston IL.\n\nAbstract\nMy work addresses the need for a theoretical framewo
rk to evaluate proposed caps on credit card interest rates and swipe fees
by developing a dynamic model that produces usable insights into the patte
rns and interdependence of consumer spending\, credit use\, and repayment
choices\, merchant pricing and competition\, and the contract decisions of
card issuers. There are several key innovations. First\, I derive conditi
ons under which credit cards increase total spending instead of simply rea
llocating it (rather than assuming one or the other). This is critical sin
ce credit cards are a special type of two-sided platform: the lending aspe
ct means there is scope for increasing transaction value beyond the impact
of reducing buying frictions. Second\, I explicitly model consumer demand
given credit access in equilibrium and show how this affects merchant pri
cing and entry\, rather than assuming fixed merchants or that demand and e
lasticities for goods purchased with credit cards are invariant in consume
r wealth. Third\, I study which consumers fall into repayment traps and wh
y. Preliminary results identify overlooked mechanisms and externalities wh
ich have important implications for the total and distributional impact of
rate caps\, fee caps\, and increased competition\, and for optimal regula
tion of credit cards in general.\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/80/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Oleg Kirillov
DTSTART:20260402T161500Z
DTEND:20260402T171500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/81
DESCRIPTION:by Oleg Kirillov as part of Northwestern Applied Mathematics S
eminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\nAbstract: T
BA\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/81/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Xiangyi Meng (Rensselaer Polytechnic Institute)
DTSTART:20260305T171500Z
DTEND:20260305T181500Z
DTSTAMP:20260315T025504Z
UID:Modeling_and_Computation/82
DESCRIPTION:Title: The shape of physical networks\nby Xiangyi Meng (Ren
sselaer Polytechnic Institute) as part of Northwestern Applied Mathematics
Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\n\nAbstrac
t\nThe brain’s connectome and the vascular system are examples of physic
al networks—tangible\, web-like objects that exist in real space (not ju
st in our papers). This physical reality means these networks combine a gr
aph structure\, describing their topological connectivity\, with a physica
l structure\, capturing the shape of all nodes and links. How do we best d
escribe this physical structure? Naturally\, we model it as a geometric ob
ject\, i.e.\, a manifold embedded in 3D space. To do this\, we turn to an
unexpected mathematical tool: the framework of covariant closed string fie
ld theory\, developed in the 1980s. This framework provides an exact corre
spondence between network-like graphs and smooth surfaces. We show that\,
as interpreted by this string-theoretical framework\, geometric objects ac
quire network shapes precisely because they tend to minimize their surface
areas. We developed both a Riemann surface formulation and a numerical al
gorithm to simulate this minimization process\, finding that it predicts s
tructural features challenging traditional explanations of network formati
on. Specifically\, this minimization predicts the emergence of trifurcatio
ns and branching angles that\, while defying conventional models such as S
teiner graphs\, are in excellent agreement with the local tree-like organi
zation of physical networks across diverse domains\, from human neurons to
corals. We conclude by discussing potential applications of this fundamen
tal discovery\, from interpreting structural changes in neurological disor
ders to designing novel metamaterials. \n\n(A popular summary of the work
can be found at: Finally A Use for String Theory! https://www.youtube.com/
watch?v=Hj5b0ieVWSo )\n
LOCATION:https://researchseminars.org/talk/Modeling_and_Computation/82/
END:VEVENT
END:VCALENDAR