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BEGIN:VEVENT
SUMMARY:Victor Barranca (Swarthmore College)
DTSTART:20221129T171500Z
DTEND:20221129T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/1
DESCRIPTION:Title: Reconstruction of Neuronal Network Connectivity an
d Rivalrous Percepts Via Compressive Sensing of Network Dynamics\nby V
ictor Barranca (Swarthmore College) as part of Northwestern Applied Mathem
atics Seminar\n\nLecture held in M416 Tech Northwestern Evanston.\n\nAbstr
act\nNeuronal network connectivity demonstrates sparsity on multiple spati
al scales and natural stimuli also possess sparse representations in numer
ous domains. In this talk\, we underline the role of sparsity in the effic
ient encoding of network connectivity and inputs through nonlinear neurona
l network dynamics. Addressing the fundamental challenge of recovering the
structural connectivity of large-scale neuronal networks\, we leverage pr
operties of the balanced dynamical regime and compressive sensing theory t
o develop a theoretical framework for efficiently reconstructing sparse ne
twork connections through measurements of the network response to a relati
vely small ensemble of random stimuli. We further utilize sparse recovery
ideas to probe the neural correlates of binocular rivalry through dynamic
percept reconstructions based on the activity of a two-layer network model
with competing downstream pools driven by disparate image stimuli. The re
sultant model dynamics agree with key experimental observations and give i
nsights into the excitation/inhibition hypothesis for autism.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Richard Braun (University of Delaware)
DTSTART:20230131T171500Z
DTEND:20230131T181500Z
DTSTAMP:20260404T110656Z
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 p
art of Northwestern Applied Mathematics Seminar\n\nLecture held in M416 Te
ch Northwestern Evanston.\n\nAbstract\nThe tear film is a thin fluid multi
layer left on the eye surface after a blink. A good tear film is essentia
l for health and proper function of the eye. Millions of people have a co
ndition 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 oc
ular surface damage. However\, there is little quantitative data about te
ar film failure\, often called tear break up (TBU). Currently\, it is not
possible to directly measure important variables such as tear osmolarity (
saltiness) 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 fl
uorescein (for visualization). We have extracted data for 15 healthy subje
cts resulting in 467 instances of TBU. Using parameter identification from
fits to appropriate math models\, we estimate which mechanisms are most i
mportant in each instance and determine critical variables such as osmolar
ity within regions of TBU. Not only is new data obtained\, but far more da
ta\, enabling statistical methods to be applied. So far\, the methods prov
ide baseline data for TBU in healthy subjects\; future work will produce d
ata from DED subjects.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Keaton Burns (Massachusettes Institute of Technology)
DTSTART:20230207T171500Z
DTEND:20230207T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/3
DESCRIPTION:Title: Solving Partial Differential Equations Exactly Ove
r Polynomials\nby Keaton Burns (Massachusettes Institute of Technology
) as part of Northwestern Applied Mathematics Seminar\n\nLecture held in M
416 Tech Northwestern Evanston.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:David Bortz (University of Colorado Boulder)
DTSTART:20230221T171500Z
DTEND:20230221T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/5
DESCRIPTION:Title: The Surprising Robustness and Computational Effici
ency of Weak Form System Identification\nby David Bortz (University of
Colorado Boulder) as part of Northwestern Applied Mathematics Seminar\n\n
Lecture held in M416 Tech Northwestern Evanston.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Daniel Wells (Santa Ana Bio\, Inc.)
DTSTART:20230228T171500Z
DTEND:20230228T181500Z
DTSTAMP:20260404T110656Z
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
Northwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech Nort
hwestern Evanston.\n\nAbstract\nSingle cell transcriptomics has revolution
ized immunology and driven the emergence of systems-level approaches in im
munology. However\, existing technologies work only on dissociated cells a
nd lose valuable tissue context. Single cell spatial transcriptomics is an
emerging field which leverages large scale profiling of RNA and protein i
n situ to measure the state of individual cells within intact tissues. Her
e we will provide an overview of single cell genomic approaches\, their us
es\, and demonstrate ways single cell spatial transcriptomics can augment
understanding of immunology. Particular focus will be paid to emerging ana
lytic approaches to extract differentiated signal from these data. FInally
\, we will provide an example of how these approaches can be applied in th
e setting of autoimmunity.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eva Kanso (University of Southern California)
DTSTART:20230404T161500Z
DTEND:20230404T171500Z
DTSTAMP:20260404T110656Z
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://stable.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:20260404T110656Z
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://stable.researchseminars.org/talk/Modeling_and_Computation
/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gwynn Elfring (University of British Columbia)
DTSTART:20230418T161500Z
DTEND:20230418T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/10
DESCRIPTION:Title: Active Matter in Inhomogeneous Environments\n
by Gwynn Elfring (University of British Columbia) as part of Northwestern
Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evan
ston IL.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Osman Basaran (Purdue University)
DTSTART:20230502T161500Z
DTEND:20230502T171500Z
DTSTAMP:20260404T110656Z
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://stable.researchseminars.org/talk/Modeling_and_Computation
/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sung Ha Kang (Georgia Institute of Technology)
DTSTART:20230509T161500Z
DTEND:20230509T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/12
DESCRIPTION:Title: Identifying Differential Equations with Numerical
Methods: Time Evolution\, Subspace Pursuit and Weak Form\nby Sung Ha
Kang (Georgia Institute of Technology) as part of Northwestern Applied Mat
hematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\nA
bstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tiffany Shaw (University of Chicago)
DTSTART:20230516T161500Z
DTEND:20230516T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/13
DESCRIPTION:Title: Fast jet stream winds get faster under climate ch
ange\nby Tiffany Shaw (University of Chicago) as part of Northwestern
Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evan
ston IL.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Linda Petzold (University of California\, Santa Barbara)
DTSTART:20230522T210000Z
DTEND:20230522T221500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/14
DESCRIPTION:Title: The Roles and Consequences of Randomness in Biolo
gical Systems\nby Linda Petzold (University of California\, Santa Barb
ara) as part of Northwestern Applied Mathematics Seminar\n\nLecture held i
n M416 Tech Northwestern Evanston IL.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Linda Petzold (University of California\, Santa Barbara)
DTSTART:20230523T161500Z
DTEND:20230523T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/15
DESCRIPTION:Title: Interpretable Polynomial Neural ODEs\nby Lind
a Petzold (University of California\, Santa Barbara) as part of Northweste
rn Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern E
vanston IL.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Christine Heitsch (Georgia Institute of Technology)
DTSTART:20231003T161500Z
DTEND:20231003T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/17
DESCRIPTION:Title: How Can Discrete Mathematics Improve RNA Folding
Predictions\nby Christine Heitsch (Georgia Institute of Technology) as
part of Northwestern Applied Mathematics Seminar\n\nLecture held in M416
Tech Northwestern Evanston IL.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Aleksandra Walczak (ENS\, Paris)
DTSTART:20231010T161500Z
DTEND:20231010T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/18
DESCRIPTION:Title: Mathematics of Life Series: Formation of Immune R
epertoire\nby Aleksandra Walczak (ENS\, Paris) as part of Northwestern
Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Eva
nston IL.\n\nAbstract\nLink: https://northwestern.zoom.us/j/94392051105\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sam Kriegman (Northwestern University)
DTSTART:20231017T161500Z
DTEND:20231017T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/19
DESCRIPTION:Title: Teaching Evolution Calculus: Efficient Automatic
Design of Robots\nby Sam Kriegman (Northwestern University) as part of
Northwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech Nor
thwestern Evanston IL.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/19/
END:VEVENT
BEGIN:VEVENT
SUMMARY:M. Graham (UW Madison)
DTSTART:20231023T210000Z
DTEND:20231023T220000Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/20
DESCRIPTION:Title: Data\, Dynamics\, and Manifolds: Machine Learning
Approaches for Modeling and Controlling Complex Flows\nby M. Graham (
UW Madison) as part of Northwestern Applied Mathematics Seminar\n\nLecture
held in M416 Tech Northwestern Evanston IL.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sky Nicholson (Northwestern University)
DTSTART:20231031T161500Z
DTEND:20231031T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/21
DESCRIPTION:Title: How to Quantify Rare-Events From Microscopic Kine
tics Using Tensor Networks\nby Sky Nicholson (Northwestern University)
as part of Northwestern Applied Mathematics Seminar\n\nLecture held in M4
16 Tech Northwestern Evanston IL.\n\nAbstract\nMolecules can undergo react
ions and diffusion through space\, creating the cornucopia of patterns we
observe in nature. Understanding how these patterns emerge is challenging
to study due to the immense separation of scales between the fast microsco
pic dynamics and the macroscopic pattern. A classic example of such a patt
ern is bistability\, where a system will spontaneously switch between two
macroscopic states of the system. Quantifying the rate of switching histor
ically has relied on waiting for exponentially rare events in the system t
o be observed. Ensembles of such events lead to estimates of kinetic rates
. In this work we show how to calculate rare macroscopic rates from high-d
imensional reaction diffusion systems without resorting to sampling techni
ques. Instead\, we exploit and extract observables such as macroscopic rat
es by evolving the ensemble of all possible trajectories. The foundation o
f this work is based on using the Doi-Peliti formalism to encode the chemi
cal master equation into a second-quantized form. This form allows chemica
l networks to be readily evolved using efficient tensor network methods. O
ur results are illustrated using an adapted version of the bistable Sch¨o
gl model with diffusion. We calculate rates over five-orders of magnitude
for large systems (∼ 3 × 1015 microstates) and show strong agreement to
kinetic-Monto Carlo simulations and the more advanced forward flux sampli
ng method. Our Doi-Peliti tensor network procedure demonstrates sub-expone
ntial scaling in computational expense\, while bypassing complications due
to sampling errors or needing intimate knowledge of the reaction network
as is the case with more advanced sampling methods.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Thierry Mora (ENS\, Paris)
DTSTART:20231107T171500Z
DTEND:20231107T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/22
DESCRIPTION:Title: Mathematics of Life Series: Statistical Mechanics
of Collective Behavior\nby Thierry Mora (ENS\, Paris) as part of Nort
hwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwes
tern Evanston IL.\n\nAbstract\nSome animal groups behave in a highly coord
inated way\, reminiscent of ordered phases in physics. However\, animals a
re also heterogeneous\, have memory\, and operate out of equilibrium. I wi
ll present recent attempts at modeling the complex dynamics of social grou
ps of mice interacting freely in a controlled environment. I will then ass
ess how far from equilibrium collective behaviour might be\, both in recor
dings of real bird flocks and in flocking models.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Milo Lin (UT Southwestern)
DTSTART:20231128T171500Z
DTEND:20231128T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/23
DESCRIPTION:Title: Mathematics of Life Seminar Series: Thermodynamic
Limits of Molecular Computation\nby Milo Lin (UT Southwestern) as par
t of Northwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech
Northwestern Evanston IL.\n\nAbstract\nLiving systems update their status
by altering the probability distribution of stochastically rearranging mo
lecules in response to a change in the system parameters. These updates co
nstitute molecular computational steps. Due to the presence of thermodynam
ic driving forces\, typically in the form of chemical gradients\, these co
mputations convert a molecular system from one non-equilibrium steady stat
e to another. Because such steady states are energetically costly to maint
ain\, the question arises as to why nature has evolved this computational
scheme. I will discuss a thermodynamic limit on computation. Namely\, for
any molecular system performing any computational step\, the maximum infor
mation gained in the computation is shown to be a simple function of the t
hermodynamic force. Therefore\, the presence of thermodynamic forces\, and
the expenditure of energy\, allows biomolecular systems to convert modest
changes in input into striking changes in output that would be surprising
or impossible at equilibrium.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Niall Mangan and Katelyn Leisman (Northwestern University)
DTSTART:20231114T171500Z
DTEND:20231114T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/24
DESCRIPTION:Title: Flushed with Insights: The Promising Potential of
Poop-Based Testing for Public Health\nby Niall Mangan and Katelyn Lei
sman (Northwestern University) as part of Northwestern Applied Mathematics
Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\n\nAbstrac
t\nEstimating the prevalence of infectious disease in a community is usefu
l for public health resource allocation\, policy making\, and messaging. W
hen diseases such as COVID-19 become endemic in the community it is essent
ial to have passive indicators that do not depend on voluntary testing dat
a. Our team is working with public health departments to use wastewater to
inform our understanding of COVID-19 prevalence in communities throughout
Illinois. We have developed a generalized methodology to improve the pred
ictive power of wastewater from treatment plants in the Chicago area. Conn
ecting measured SARS-CoV-2 RNA to community prevalence is challenging\, du
e to changes in the contributing population\, the variable rate of wastewa
ter flow\, and the complexity of wastewater media\, which impacts RNA deca
y rates and lab measurement accuracy. To quantify the impact of these fact
ors we also track other viruses including pepper mild mottle virus (PMMoV)
\, a biomarker for the number of people contributing to the wastewater\, a
nd bovine coronavirus (BCoV)\, a lab process recovery control. We build an
d compare a set of multi-linear regression models\, which incorporate PMMo
V\, BCoV\, and flow rate into a corrected estimate for SARS-CoV-2 RNA conc
entration. Laboratory methods evolved rapidly during the COVID-19 pandemic
\, and we show that correction terms differ depending on the laboratory pr
ocedures used in analyzing the samples. Nonetheless\, in all cases a stati
stical correction model provides a significant improvement in terms of cor
relation with hospitalizations and trend analysis over doing no correction
.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/24/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Albane Thery (University of Pennsylvania)
DTSTART:20240123T171500Z
DTEND:20240123T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/26
DESCRIPTION:Title: Building Models For Swimmers in Complex and Confi
ned Environments\nby Albane Thery (University of Pennsylvania) as part
of Northwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech
Northwestern Evanston IL.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yue Yu (Lehigh University)
DTSTART:20240206T171500Z
DTEND:20240206T181500Z
DTSTAMP:20260404T110656Z
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\
nLecture held in M416 Tech Northwestern Evanston IL.\n\nAbstract\nDuring t
he last 20 years there has been a lot of progress in applying neural netwo
rks (NNs) to many machine learning tasks. However\, their employment in sc
ientific machine learning with the purpose of learning physics of complex
system is less explored. Differs from the other machine learning tasks suc
h as the computer vision and natural language processing problems where a
large amount of unstructured data are available\, physics-based machine le
arning tasks often feature scarce and structured measurements. \nIn th
is talk\, we will take the learning of heterogeneous material responses as
an exemplar problem\, to investigate the design of neural networks for ph
ysics-based machine learning. In particular\, we propose to parameterize t
he mapping between loading conditions and the corresponding system respons
es in the form of nonlocal neural operators\, and infer the neural network
parameters from high-fidelity simulation or experimental measurements. As
such\, the model is built as mappings between infinite-dimensional functi
on spaces\, and the learnt network parameters are resolution-agnostic: no
further modification or tuning will be required for different resolutions
in order to achieve the same level of prediction accuracy. Moreover\, the
nonlocal operator architecture also allows the incorporation of intrinsic
mathematical and physics knowledge\, which improves the learning efficacy
and robustness from scarce measurements. \nTo demonstrate the applicab
ility of our nonlocal operator learning framework\, three typical scenario
s in physics-based machine learning will be discussed: the learning of a m
aterial-specific constitutive law\, the learning of an efficient PDE solut
ion operator\, and the development of a foundational constitutive law acro
ss multiple materials. As an application\, we learn material models direct
ly from digital image correlation (DIC) displacement tracking measurements
on a porcine tricuspid valve leaflet tissue\, and show that the learnt mo
del substantially outperforms conventional constitutive models.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/27/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Geoff Vallis (Exeter)
DTSTART:20240213T171500Z
DTEND:20240213T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/28
DESCRIPTION:Title: Rainy-Bénard Convection: An Idealization of a Mo
ist Atmosphere\nby Geoff Vallis (Exeter) as part of Northwestern Appli
ed Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston
IL.\n\nAbstract\nRayleigh-Benard convection is commonly regarded as the be
nchmark system for convection in a wide variety of settings\, and its simp
licity has led to a great many theoretical\, experimental and computationa
l studies. However\, it is often regarded as irrelevant as a model for con
vection in Earth’s atmosphere because of the significant\, almost domina
ting\, influence of moisture in the latter system\, in addition to many ot
her complications. In an attempt to partially bridge the evident gap betwe
en these systems we add a condensate to the Rayleigh-Benard system but kee
p other aspects the same. The resulting ‘Rainy-Benard’ system has very
rich behavior and in this talk I’ll describe some that behavior and oth
er properties of the system.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/28/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sid Goyal (University of Toronto)
DTSTART:20240220T171500Z
DTEND:20240220T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/29
DESCRIPTION:Title: POSTPONED Mathematics of Life Seminar Series: Com
petition Across Scales in Biology\nby Sid Goyal (University of Toronto
) as part of Northwestern Applied Mathematics Seminar\n\nLecture held in M
416 Tech Northwestern Evanston IL.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/29/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Snezhana Abarzhi (U Western Adelaide (Australia))
DTSTART:20240227T171500Z
DTEND:20240227T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/30
DESCRIPTION:Title: Interface Dynamics in Ideal and Realistic Fluids<
/a>\nby Snezhana Abarzhi (U Western Adelaide (Australia)) as part of North
western Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwest
ern Evanston IL.\n\nAbstract\nInterface and mixing and their non-equilibri
um kinetics and dynamics couple micro to macro scales\, and are ubiquitous
to occur in fluids\, plasmas and materials. Stellar evolution\, plasma fu
sion\, reactive fluids\, microfluidics\, purification of water\, and nanof
abrication are a few examples of many processes to which dynamics of inter
faces is directly relevant. This talk presents the rigorous theory of the
stability of the interface – a phase boundary broadly defined. We direct
ly link the structure of macroscopic flow fields to microscopic interfacia
l transport\, quantify the contributions of macro and micro stabilization
mechanisms to interface stability\, and discover the fluid instabilities n
ever previously discussed. In ideal and realistic fluids\, the interface s
tability is set primarily by the interplay of the macroscopic inertial mec
hanism balancing the destabilizing acceleration\, whereas microscopic ther
modynamics create vortical fields in the bulk. By linking micro to macro s
cales\, the interface is the place where balances are achieved.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/30/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Peko Hosoi (Massachusetts Institute of Technology (MIT))
DTSTART:20240326T161500Z
DTEND:20240326T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/31
DESCRIPTION:Title: Filtration and Fluid Mechanics Inspired by the Ma
nta Ray - Reiss Lecture\nby Peko Hosoi (Massachusetts Institute of Tec
hnology (MIT)) as part of Northwestern Applied Mathematics Seminar\n\nLect
ure held 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 c
onsumed by fans. Their energy efficiency strongly depends on their filters
: reducing resistance can result in significant energy savings. We explore
novel strategies for filtration inspired by the manta ray\, which has evo
lved a system for filtering zooplankton that appears to be unlike any indu
strial filtration mechanism. Instead of a sieve strategy\, the manta deplo
ys microstructures\, which are hypothesized to instigate eddies that push
particles away from the filtration pores\, resisting clogging\, and enabli
ng the filtration of particles much smaller than the pore size. Using pert
urbation theory and asymptotics we examine two toy problems that mimic var
ious features of the filtration strategies employed by manta rays and find
that experimental data from wavy channels are consistent with our asympto
tic predictions.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/31/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Efi Efrati (Weizmann Institute of Science)
DTSTART:20240416T161500Z
DTEND:20240416T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/32
DESCRIPTION:Title: Frustrated Assemblies: Describing Matter from Wit
hin\nby Efi Efrati (Weizmann Institute of Science) as part of Northwes
tern Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern
Evanston IL.\n\nAbstract\nFrustrated assemblies are comprised of ill-fitt
ing building blocks whose favored local relative arrangement cannot be glo
bally realized. In fact\, most self assembled structures contain some degr
ee of frustration. In some cases\, the frustration is locally resolved and
leads to little or no structural consequence\, while in other cases it do
minates the assembly's size\, shape\, and response properties. In this
talk\, I will present different manifestations of geometric frustration a
s they naturally arise in molecular crystals\, liquid crystals\, spin syst
ems\, and nanoparticle assemblies. To theoretically study these assemblies
we resort to an intrinsic approach in which matter is described only thro
ugh local properties available to an observer residing within the material
. The frustration is then quantified by the geometric compatibility condit
ions whose structure allows us to classify the frustration and predict the
assembly's behavior without explicitly solving for the ground state of th
e system.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/32/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ehud Yariv (Technion - Israel Institute of Technology)
DTSTART:20240430T161500Z
DTEND:20240430T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/33
DESCRIPTION:Title: Shocks and Caps in Drop Electrohydrodynamics\
nby Ehud Yariv (Technion - Israel Institute of Technology) as part of Nort
hwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwes
tern Evanston IL.\n\nAbstract\nThe problem of electrohydrodynamic drop def
ormation 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\
, including analytical expressions for the electrohydrodynamic flow engend
ered within and outside of the drop by the electric field acting on its ow
n induced interfacial charge\, and a simple function of the permittivity\,
conductivity and viscosity drop-to-background ratios discriminating betwe
en prolate or oblate deformation. In this talk\, we will employ nume
rical and asymptotic tools to explore the effects of interfacial-charge co
nvection\, which were neglected by Taylor but become important at strong e
lectric fields. In particular\, we will analyze (in 2D\, for simplicity) h
ow Taylor’s fore-aft symmetric solution evolves as the electrical Reynol
ds number is increased from zero to arbitrarily large values. What we shal
l 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://stable.researchseminars.org/talk/Modeling_and_Computation
/33/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pankaj Mehta (Boston University)
DTSTART:20240507T161500Z
DTEND:20240507T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/34
DESCRIPTION:Title: Mathematics of Life Seminar Series: Randomness\,
Complexity\, and the Biological Frontier\nby Pankaj Mehta (Boston Univ
ersity) as part of Northwestern Applied Mathematics Seminar\n\nLecture hel
d in M416 Tech Northwestern Evanston IL.\n\nAbstract\nThe towering success
es of twentieth century theoretical physics were marked by two guiding pri
nciples: symmetry and energy functionals (reflecting equilibrium dynamics)
. Yet how we can exploit these principles to develop a theory of living sy
stems is unclear since the biological world is composed of heterogeneous\,
interacting components operating out of equilibrium. In this talk\, I wil
l 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-insp
ired constraints. I will focus on showing how this approach can be used to
make close connection with experiments by presenting three vignettes focu
sing on: (i) theory-inspired techniques for visualizing single-cell transc
riptomics data for cellular identity\, (ii) understanding how the interpla
y between cross-feeding and competition shapes microbial ecosystems and (i
ii) the emergence of chaos in the ecosystems with non-reciprocal interacti
on.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/34/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Andrew Stuart (California Institute of Technology)
DTSTART:20240521T161500Z
DTEND:20240521T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/35
DESCRIPTION:Title: Operator Learning: Algorithms\, Analysis and Appl
ications\nby Andrew Stuart (California Institute of Technology) as par
t of Northwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech
Northwestern Evanston IL.\n\nAbstract\nApproximating operators that map b
etween function spaces can be useful for accelerating systems level tasks
in scientific computing\, and for discovering computational models from da
ta. In its most basic form\, learning an operator may be cast as a form of
supervised learning in which the input-output pairs are functions. The ta
lk will overview a variety of specific approximation architectures that ha
ve been developed in the last five years\; emerging theoretical results ex
plaining the approximation capabilities of the architectures will be expla
ined\; and applications to constitutive modeling (plasticity) and inverse
problems (fluid mechanics) will be given.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/35/
END:VEVENT
BEGIN:VEVENT
SUMMARY:James Fitzgerald (Northwestern University)
DTSTART:20240305T171500Z
DTEND:20240305T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/36
DESCRIPTION:Title: Bridging Theoretical Neuroscience and Neural Data
Science with Simple Models\nby James Fitzgerald (Northwestern Univers
ity) as part of Northwestern Applied Mathematics Seminar\n\nLecture held i
n M416 Tech Northwestern Evanston IL.\n\nAbstract\nNeuroscience is enterin
g a data-rich era that requires computational approaches and opens excitin
g new possibilities for theory building. Here I will describe how my resea
rch group couples neural data science and abstract theoretical modeling to
build interpretable models of diverse neural systems. In my first illustr
ative example\, I’ll explain our efforts to uncover synaptic plasticity
mechanisms that allow flies to learn probabilistic reward associations and
direct decision making. I’ll then shift to larval zebrafish and whole-b
rain imaging to explain how we build and analyze neural network models of
sensorimotor processing and behavior.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/36/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Peko Hosoi (Massachusetts Institute of Technology (MIT))
DTSTART:20240327T210000Z
DTEND:20240327T220000Z
DTSTAMP:20260404T110656Z
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 M416 Tech Northwestern Evanston IL.\n\nAbstract\nIn most professional
sports\, every physical attribute of an athlete that can be measured is tr
acked and recorded. There exists an abundance of (relatively) high quality
data — in football\, basketball\, baseball\, cricket\, etc. — which m
akes sports an ideal testing ground for new analyses and algorithms. In th
is talk I will describe a few studies that lie at the intersection of spor
ts and data. Topics may include: the origin of the increase in home runs i
n Major League Baseball\; the public health impact of allowing fans in Ame
rican football stadiums during the pandemic\; the role of skill and chance
in sports and other activities\; measuring “court sense” i.e. an athl
ete’s decision-making ability in basketball\; and the design of optimal
running shoes.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/37/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Maciej Lisicki (University of Warsaw and UPenn)
DTSTART:20240409T161500Z
DTEND:20240409T171500Z
DTSTAMP:20260404T110656Z
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
Northwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech Nor
thwestern Evanston IL.\n\nAbstract\nA look into the microworld reveals ple
thora of swimming microorganisms\, which display a rich variety of shapes
and swimming gaits. Despite this diversity\, physics of microscale imposes
universal limitations on their propulsion strategies. In my talk\, I will
review the basic properties of Stokes flows and their consequences on swi
mming. Next\, I will show an artificial system of microscale oil droplets
that have the ability to swim due to a surface phase transition driven by
environmental temperature fluctuations. I will demonstrate how a coarse-gr
ained elastohydrodynamic model can be successfully employed to quantitativ
ely describe the motion of droplets. I will also show a couple of other ex
amples where a simplified elastohydrodynamic model proves useful for the p
rediction of diffusive properties.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/38/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Naomi Oppenheimer (Tel Aviv University\, Israel)
DTSTART:20240312T180000Z
DTEND:20240312T190000Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/39
DESCRIPTION:Title: Hydrodynamic Hamiltonians of Active Two-dimension
al Fluids\nby Naomi Oppenheimer (Tel Aviv University\, Israel) as part
of Northwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech
Northwestern Evanston IL.\n\nAbstract\nI will describe two biologically in
spired systems that can be analyzed using the same hydrodynamic Hamiltonia
n formalism. The first is ATP synthase proteins\, which rotate in a biolog
ical membrane. The second is swimming micro-organisms such as bacteria or
algae confined to a two-dimensional film. I will show that in both cases\,
the active systems self-assemble into distinct structural states --- the
rotating proteins rearrange into a hexagonal lattice\, whereas the micro-s
wimmers evolve into a zig-zag configuration with a particular tilt. While
the two systems differ both on the microscopic\, local interaction\, as we
ll as the emerging\, global structure\, their dynamics originate from simi
lar geometrical conservation laws applicable to a broad class of fluid flo
ws. I will then show experiments and simulations in which the Hamiltonian
is perturbed\, leading to different and surprising steady-state configurat
ions.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/39/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tom Dean (Breakthrough Energy)
DTSTART:20240423T161500Z
DTEND:20240423T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/40
DESCRIPTION:Title: Contrail Climate Impacts: Modeling and Mitigation
Strategies\nby Tom Dean (Breakthrough Energy) as part of Northwestern
Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Eva
nston IL.\n\nAbstract\nAviation accounts for approximately 3.5% of global
anthropogenic climate forcing. Of this\, less than half is attributed to t
he CO2 output from fuel combustion. Nearly half of the total climate impac
t of aviation can be attributed to contrail cirrus – cirrus clouds that
have been seeded by the exhaust plumes of the aircraft – though with con
siderable uncertainty. Given that only around 2-3% of all flights were are
likely responsible for 80% of the global annual contrail climate forcing\
, a potential contrail mitigation strategy could involve re-routing this s
ubset of flights to minimize the formation of strongly warming contrails.
Studies have shown that such strategies would require as little as 0.2% ad
ditional fuel burn. Implementing such a strategy requires an accurate abi
lity to forecast contrail impacts\, which in turn requires accurate modeli
ng of microphysical atmospheric processes at flight levels. In this talk w
e will give an overview of contrail modeling and describe the grid-based C
ontrail Cirrus Prediction model (CoCiP)\, whose output is designed to be i
nput as a layer in flight planning tools.\n
LOCATION:https://stable.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:20260404T110656Z
UID:Modeling_and_Computation/41
DESCRIPTION:Title: Active Fractal Networks with Stochastic Force Mon
opoles and Force Dipoles Unravel Subdiffusion of Chromosomal Loci\nby
Rony Granek (Ben Gurion University of the Negev) as part of Northwestern A
pplied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evans
ton IL.\n\nAbstract\nMotivated by the well-known fractal packing of chroma
tin\, we study the Rouse-type dynamics of elastic fractal networks with em
bedded\, stochastically driven\, active force monopoles and force dipoles
that are temporally correlated. We compute\, analytically – using a gene
ral theoretical framework – and via Langevin dynamics simulations\, the
mean square displacement (MSD) of a network bead. Following a short time s
uperdiffusive behavior\, force monopoles yield anomalous subdiffusion with
an exponent identical to that of the thermal system. In contrast\, force
dipoles do not induce subdiffusion\, and the early superdiffusive MSD cros
ses over to a relatively small\, system-size-independent saturation value.
In addition\, we find that force dipoles may lead to ``crawling" rotation
al motion of the whole network\, reminiscent of that found for triangular
micro-swimmers and consistent with general theories of the rotation of def
ormable bodies. Moreover\, force dipoles lead to network collapse beyond a
critical force strength\, which persists with increasing system size\, si
gnifying a true first-order dynamical phase transition. We apply our resul
ts to the motion of chromosomal loci in bacteria and yeast cells' chromati
n\, where anomalous sub-diffusion\, MSD∼ t^ν with ν≃ 0.4\, were foun
d in both normal and ATP-depleted cells\, albeit with different apparent d
iffusion coefficients. We show that the combination of thermal\, monopolar
\, and dipolar forces in chromatin is typically dominated by the active mo
nopolar and thermal forces\, explaining the observed normal cells vs the A
TP-depleted cells behavior.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/41/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Krishna Shrinivas (Northwestern University)
DTSTART:20241008T161500Z
DTEND:20241008T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/42
DESCRIPTION:Title: The Many Phases of a Cell\nby Krishna Shriniv
as (Northwestern University) as part of Northwestern Applied Mathematics S
eminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\n\nAbstract\
nCells routinely orchestrate reactions\, interactions\, and transport amon
gst billions of biomolecules in a crowded environment to perform the diver
se tasks that underpin life. Rather than occurring in a well-mixed milieu\
, biomolecules self-organize into dozens of membrane-lacking compartments
called condensates that enable key biological functions and are aberrant i
n disease. I will introduce how phase transitions are emerging as a paradi
gm underlying condensate assembly and function in cells. During the talk\,
I will describe our efforts that bridge statistical physics\, applied mat
hematics\, and computation to predict emergent multiphase behavior in high
ly multicomponent soft materials and how such materials can be designed to
perform information processing or computational tasks.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/42/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Trevor GrandPre (Princeton University)
DTSTART:20241015T161500Z
DTEND:20241015T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/43
DESCRIPTION:Title: Model-free Inference from Time-series Data\nb
y Trevor GrandPre (Princeton University) as part of Northwestern Applied M
athematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\
n\nAbstract\nDrawing inferences from experimental data often involves impo
sing models\, which can lead to inaccurate conclusions. Theory sometimes p
oints to quantities that are significant independent of the underlying mec
hanisms\, but making accurate model-free estimates of these quantities can
be hard because finite data generates systematic errors. I present two ca
ses where we develop new methods to address and correct these errors: (1)
extracting long-term population growth from single-cell lineage data and (
2) estimating the evidence for the arrow of time in patterns of neural act
ivity. For population growth\, key observables are the number of divisions
and generation times along a lineage for a fixed time. Simple growth rate
estimators suffer from finite-time bias at short times\; this bias scales
inversely with time and can be corrected. At longer times\, rare events i
ntroduce a linearization bias\, causing an abrupt phase transition explain
ed by a simple model of disordered systems. Our approach yields accurate e
stimates provided the lineage counts and lengths stay below the critical p
oint\, allowing inference of how mutations and physiological variations im
pact fitness. In the case of neural activity\, the relevant observables ar
e the moments of activity and the waiting times between these moments. Est
imating the irreversibility—quantified by the Kullback-Leibler divergenc
e between the distribution of forward and backward trajectories—faces si
milar biases. Finding the systematic dependence of these biases on sample
size allows for accurate estimates\, including detecting systems that obey
detailed balance\, and opens a path to exploring how the brain represents
the arrow of time. Generally\, this new understanding of how model-free e
stimators rely on a complex order of limits of the amount of data and the
length of each sample may allow quantitative understanding of other releva
nt processes such as gene regulation\, cell-cycle dynamics\, and signal tr
ansduction.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/43/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pedram Hassanzadeh (The University of Chicago)
DTSTART:20241029T161500Z
DTEND:20241029T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/44
DESCRIPTION:Title: Integrating the Spectral Analyses of Neural Netwo
rks and Nonlinear Physics for Explainability\, Generalizability\, and Stab
ility\nby Pedram Hassanzadeh (The University of Chicago) as part of No
rthwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech Northw
estern Evanston IL.\n\nAbstract\nIn recent years\, there has been substant
ial interest in using deep neural networks (NNs) to improve the modeling a
nd prediction of complex\, multiscale\, nonlinear dynamical systems such a
s turbulent flows and Earth’s climate. In idealized settings\, there has
been some progress for a wide range of applications from data-driven spat
io-temporal forecasting to long-term emulation to subgrid-scale modeling.
However\, to make these approaches practical and operational\, i.e.\, scal
able to real-world problems\, a number of major questions and challenges n
eed to be addressed. These include 1) instabilities and the emergence of u
nphysical behavior\, e.g.\, due to how errors amplify through NNs\, 2) lea
rning in the small-data regime\, 3) interpretability based on physics\, an
d 4) out-of-distribution generalization (e.g.\, extrapolation to different
parameters\, forcings\, and regimes) which is essential for applications
to non-stationary systems such as a changing climate. While some progress
has been made in addressing (1)-(4)\, e.g.\, doing transfer learning for g
eneralization\, these approaches have been often ad-hoc\, as currently the
re is no rigorous framework to analyze deep NNs and develop systematic and
general solutions to (1)-(4). In this talk\, I will discuss some of the a
pproaches to address (1)-(4)\, for example\, once we identify spectral bia
s as the cause of instabilities in state-of-the-art weather models like Pa
ngu-weather\, GraphCast\, and FourCastNet. Then I will introduce a new fra
mework that combines the spectral (Fourier) analyses of NNs and nonlinear
physics\, and leverages recent advances in theory and applications of deep
learning\, to move toward rigorous analysis of deep NNs for applications
involving dynamical systems. For example\, this approach can guide and exp
lain transfer learning and pruning in such applications. I will use exampl
es from turbulence modeling and weather/climate prediction to discuss thes
e methods and ideas.\n
LOCATION:https://stable.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:20260404T110656Z
UID:Modeling_and_Computation/45
DESCRIPTION:Title: The Dynamics of Particles with Ligand-receptor Co
ntacts\nby Miranda Holmes-Cerfon (The University of British Columbia)
as part of Northwestern Applied Mathematics Seminar\n\nLecture held in M41
6 Tech Northwestern Evanston IL.\n\nAbstract\nOne way to glue objects toge
ther at the nanoscale or microscale is by ligand-receptor interactions\, w
here short sticky hair-like ligands stick to receptors on another surface\
, much like velcro on the nanoscale. Such interactions are common in biolo
gical systems\, such as white blood cells\, virus particles\, cargo in the
nuclear pore complex\, etc\, and they are also useful in materials scienc
e\, where coating colloids with single-stranded DNA creates particles with
programmable interactions. In these systems\, the ligand-receptor interac
tions not only hold particles together\, but also influence their dynamics
. How do such particles move? Do they “roll” on each others’ surface
s\, as is commonly thought? Or could they slide? And does it matter? In th
is talk I will introduce our modelling and experimental efforts aimed at u
nderstanding the coarse-grained dynamics of particles with ligand-receptor
interactions. Our models predict these interactions can change the partic
les' effective diffusion by orders of magnitude. Our experiments\, using D
NA-coated colloids\, verify this dramatic dynamical slowdown\, but also sh
ow other dynamical features not yet captured by our models\, which suggest
new avenues for exploration.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/45/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mariela Petkova (Harvard University)
DTSTART:20241112T171500Z
DTEND:20241112T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/46
DESCRIPTION:Title: Carving Circuits from Correlative Connectomics\nby Mariela Petkova (Harvard University) as part of Northwestern Applied
Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL
.\n\nAbstract\nTracing the wiring diagram of a neural circuit is a powerfu
l approach to test\ncomputational models of brain function. Connectomics
– the mapping of\nneurons and their connections in the brain – poses f
ormidable technical and\nconceptual challenges. The former entails the acq
uisition and reduction of\nvast amounts of electron microscopy image data
to connectivity matrices\,\nachieved through multi-year\, multi-team colla
borative efforts. The latter\nchallenge is the problem of coarse-graining
the connectivity matrices to\nneural circuits which exhibit neural activit
y and function. I will describe both\nchallenges in the context of mapping
the nervous system of a small\nvertebrate – the larval zebrafish. In th
e same animal\, we pair electron\nmicroscopy with functional information f
rom light microscopy to interrogate\nneural circuit models for animal beha
vior from sensory inputs to motor output.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/46/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ertugrul Ozbudak (Northwestern University)
DTSTART:20241119T171500Z
DTEND:20241119T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/47
DESCRIPTION:Title: Reengineering Somite Segmentation without the Ver
tebrate Segmentation Clock\nby Ertugrul Ozbudak (Northwestern Universi
ty) as part of Northwestern Applied Mathematics Seminar\n\nLecture held in
M416 Tech Northwestern Evanston IL.\n\nAbstract\nSomitogenesis establishe
s the segmental pattern of the vertebral column. A molecular segmentation
clock sets the pace of somite formation while a spatial gradient of ERK ac
tivity instructs segment boundary positions. However\, how cells are prime
d to form a segment boundary at discrete locations and how the clock and g
radient are mechanistically integrated were unclear. We developed transgen
ic reporters for the segmentation clock and the gradient in zebrafish embr
yos. We show that the segmentation clock periodically inhibits the gradien
t\, therefore projecting its oscillation onto the gradient. Pulsatile inhi
bition of the gradient can fully substitute for the role of the clock\, an
d other targets of the clock are dispensable for sequential segmentation.
We propose a “Clock-dependent Oscillatory Gradient (COG)” model in whi
ch the clock periodically triggers discrete jumps of the positional inform
ation. Computational simulations of the COG model explain all experimental
observations\; the new model effectively replaces a long-standing textboo
k model.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/47/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Evelyn Tang (Rice University)
DTSTART:20241203T171500Z
DTEND:20241203T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/48
DESCRIPTION:Title: Robust Dynamics and Function in Stochastic Topolo
gical Systems\nby Evelyn Tang (Rice University) as part of Northwester
n Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Ev
anston IL.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/48/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Luis Amaral (Northwestern University)
DTSTART:20250114T171500Z
DTEND:20250114T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/49
DESCRIPTION:Title: Science Is an All-You-Can-Eat Buffet and I Am Not
Dieting\nby Luis Amaral (Northwestern University) as part of Northwes
tern Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern
Evanston IL.\n\nAbstract\nIn the old days\, mathematicians were alchemist
s\, astronomers\, astrologers\, chemists\, demographers\, philosophers\, s
urveyors\, and so many other things. Even as recently as 1944\, Schrödin
ger could write about “how can the events in space and time which take p
lace within the spatial boundary of a living organism be accounted for by
physics and chemistry?" In modern times\, it seems that if you do not sti
ck with your discipline's scope then you are at risk of being dismissed as
an interloper or a hack. But beauty can be found in many different areas
of knowledge and rigor can be used to address phenomena from areas lackin
g rigorous abstractions. I will indulge in describing some examples from m
y lab’s recent research.\n
LOCATION:https://stable.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:20260404T110656Z
UID:Modeling_and_Computation/51
DESCRIPTION:Title: Walking Droplets & Galloping Bubbles\nby Pedr
o Saenz (University of North Carolina at Chapel Hill) as part of Northwest
ern Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern
Evanston IL.\n\nAbstract\n"Blending experiments\, simulations and theory\,
we will discuss two different problems that are moti-vated by fundamenta
l questions in physics and engineering.\nIn the first part\, we present a
classical wave-particle analog of Anderson localization using walking dro
plets\, or “walkers\,” which self-propel across a vibrating fluid bat
h via a resonant interaction with their guiding wave field. These droplet
s push the boundaries of classical mechanics by exhibiting behaviors previ
ously thought to be exclusive to the quantum realm. Investigating the erra
tic motion of walkers over submerged random topographies\, we demonstrate
the emergence of localized statistics analogous to those of quantum partic
les. Analysis of walker trajectories reveals a suppression of diffusion w
hen the guiding wave field extends over the disordered topography\, drive
n by a wave-mediated resonant coupling that generates an attractive wave p
otential. This hydrodynamic quantum analog illustrates how a classical par
ticle may localize like a wave. The second part introduces a new symmetry-
breaking mechanism that enables bubbles to “gallop” along horizontal s
urfaces in a vertically vibrated fluid chamber\, propelled by coupling be
tween shape oscillation modes. These active bubbles exhibit diverse trajec
tory regimes – rectilinear\, orbital\, and run-and-tumble – tunable by
external forcing. By leveraging periodic body deformations and inertial f
orces\, galloping bubbles achieve self-propulsion without external forcing
in their direction of motion. Proof-of-concept demonstrations illustrate
the potential of galloping locomotion for bubble manipulation\, transport
and sorting\, navigation through complex fluid networks\, and surface cle
aning."\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/51/
END:VEVENT
BEGIN:VEVENT
SUMMARY:James Stone (Institute for Advanced Study)
DTSTART:20250225T171500Z
DTEND:20250225T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/52
DESCRIPTION:Title: Astrophysical Fluid Dynamics at Exascale\nby
James Stone (Institute for Advanced Study) as part of Northwestern Applied
Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL
.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/52/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Vaseem Shaik (Northwestern University)
DTSTART:20250311T161500Z
DTEND:20250311T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/53
DESCRIPTION:Title: Active Particles in Inhomogeneous Environments\nby Vaseem Shaik (Northwestern University) as part of Northwestern Appli
ed Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston
IL.\n\nAbstract\n"Active particles are living or non-living entities that
convert stored energy to directed motion\, and a suspension of these parti
cles is termed active matter. Examples of active particles include nanorob
ots\, microorganisms\, birds\, fish\, and humans. These particles often na
vigate through inhomogeneous environments such as gradients in heat\, ligh
t\, nutrients\, fluid viscosity\, or density. They typically respond to th
ese inhomogeneities by displaying directed motion up or down the gradients
\, known as taxis. Some well-known types of taxis are chemotaxis in chemic
al/nutrient gradients\, phototaxis in light gradients\, and gravitaxis in
gravitational field.\n\nHere I focus on the μm - mm sized particles swimm
ing in the inhomogeneities in mechanical properties of fluid like fluid vi
scosity\, density or elasticity gradients. I discuss the recently understo
od taxis in viscosity gradients (viscotaxis). I also talk about how these
particles behave as light when interacting with sharp viscosity gradients\
, and how this behavior can be described by a Snell's like law. Additiona
lly\, I address taxis in elasticity or relaxation time gradients (durotaxi
s). I then discuss a new taxis in density gradients (densitaxis)\, that po
ssibly aids/hinders the diel vertical migration of planktonic organisms in
oceans. I also talk about the mixing by these particles and different way
s to quantify it. Lastly\, I discuss the effect of noise and how the afore
said inhomogeneities could be used to control active matter under confinem
ents."\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/53/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Brennan Sprinkle (Colorado School of Mines)
DTSTART:20250408T161500Z
DTEND:20250408T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/54
DESCRIPTION:Title: The Countoscope: Counting Particles to Measure Dy
namic Properties of Suspensions In and Out of Equilibrium\nby Brennan
Sprinkle (Colorado School of Mines) as part of Northwestern Applied Mathem
atics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\n\nAb
stract\nModern microscopy techniques can image complex\, microscopic syste
ms with an unprecedented resolution – but methods to analyze these image
s are much less robust. Available techniques to probe dynamics rely on rec
onstructing particle trajectories\, which can be difficult or impossible i
n some cases\, or some form of video analysis\, which can be unreliable an
d expensive. Inspired by the early work of Smoluchowski we introduce the `
Countoscope’\, a technique that near completely ameliorates these issues
by simply counting particle number fluctuations in observation boxes. By
varying properties like the size or aspect ratio of the boxes and taking d
ifferent measures of correlation between these observation boxes\, we can
`zoom’ in or out to measure individual or collective particle kinetics i
n both passive and active systems. Using colloidal suspensions as a test c
ase\, we employ a combination of experiments\, simulations\, and analytica
l theory to support our findings.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/54/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jane Kondev (Brandeis University)
DTSTART:20250128T171500Z
DTEND:20250128T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/55
DESCRIPTION:Title: The Scale-Invariant Cell\nby Jane Kondev (Bra
ndeis University) as part of Northwestern Applied Mathematics Seminar\n\nL
ecture held in M416 Tech Northwestern Evanston IL.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/55/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mark Hoefer (University of Colorado Boulder)
DTSTART:20250304T171500Z
DTEND:20250304T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/56
DESCRIPTION:Title: A Wave Theory of Waves\nby Mark Hoefer (Unive
rsity of Colorado Boulder) as part of Northwestern Applied Mathematics Sem
inar\n\nLecture held in M416 Tech Northwestern Evanston IL.\nAbstract: TBA
\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/56/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sasha Tchekhovskoy (Northwestern University)
DTSTART:20250211T171500Z
DTEND:20250211T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/57
DESCRIPTION:Title: Simulating Black Hole Feasts\, Burps\, and Firewo
rks\nby Sasha Tchekhovskoy (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://stable.researchseminars.org/talk/Modeling_and_Computation
/57/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dan Wilson (University of Tennessee Knoxville)
DTSTART:20250415T161500Z
DTEND:20250415T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/59
DESCRIPTION:Title: Phase-Amplitude-Based Techniques for Control and
Analysis of Strongly Perturbed Limit Cycle Oscillators\nby Dan Wilson
(University of Tennessee Knoxville) as part of Northwestern Applied Mathem
atics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\n\nAb
stract\nWhile phase-based reduction techniques have a rich history in the
analysis and control of oscillatory dynamical systems\, the overwhelming m
ajority of theoretical analysis in this field has been performed in the we
akly perturbed limit. Comparatively very little is understood about limit
cycle oscillators in response to strong and/or long-lasting perturbations
\, mostly due to the lack of viable reduction strategies that are valid wh
en considering strong perturbations.\n\nIn this presentation\, I will disc
uss the use of isostable coordinates\, which characterize level sets of th
e slowest decaying eigenmodes of the Koopman operator in conjunction with
phase-based techniques to yield analytically tractable reduced order model
s that are valid in the strongly perturbed regime. Applications involving
phase resetting of circadian rhythms following rapid travel across multip
le time zones illustrate the utility of these new methods in situations wh
ere standard\, phase-only techniques fail. \nI will also discuss related w
ork motivated by experimental and detailed computational studies finding t
hat coupled circadian oscillators with decreased levels of synchronization
are able to more rapidly adjust to changes in circadian time. Theoretic
al analysis reveals the dynamics of mean-field coupled oscillators can be
considered in the context of a supercritical Hopf bifurcation\, ultimately
providing an explanation for the fundamental relationship between synchro
nization and phase resetting efficiency. In the context of jet-lag recove
ry strategies\, further analysis reveals that transient desynchronization
facilitates phase resetting when the relaxation rate of the population lim
it cycle is sufficiently slow relative to the natural frequency of the pop
ulation oscillation.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/59/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Todd Murphey (Northwestern University)
DTSTART:20250422T161500Z
DTEND:20250422T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/60
DESCRIPTION:Title: Control for Embodied Learning\nby Todd Murphe
y (Northwestern University) as part of Northwestern Applied Mathematics Se
minar\n\nLecture held in M416 Tech Northwestern Evanston IL.\n\nAbstract\n
Embodied learning systems rely on motion synthesis to enable efficient and
flexible learning during continuous online deployment. Motion motivated b
y learning needs can be found throughout natural systems\, yet there is su
rprisingly little known about synthesizing motion to support learning for
robotic systems. Moreover\, robotic systems will need to collect data auto
nomously for learning\, for instance when isolated for long period of time
or when encountering novel environmental features. Learning goals create
a distinct set of control-oriented challenges\, including how to choose me
asures as objectives\, synthesize real-time control based on these objecti
ves\, impose physics-oriented constraints on learning\, and produce analys
es that certify performance and safety with limited knowledge. This talk w
ill discuss learning tasks that robots encounter\, abstractions that enabl
e regulating information content of observations\, and recent progress on
algorithms for generating action plans that facilitate learning.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/60/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chris Vogl (Lawrence Livermore National Laboratory)
DTSTART:20250506T161500Z
DTEND:20250506T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/61
DESCRIPTION:Title: Improving Global Atmosphere Simulation in Earth S
ystem Models with Multiphysics Time Integration Methods\nby Chris Vogl
(Lawrence Livermore National Laboratory) as part of Northwestern Applied
Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.
\n\nAbstract\nTo reliably predict the frequency and severity of hurricanes
\, floods\, droughts\, and other weather-driven disasters\, the efficient
simulation of Earth system models is crucial. Such an endeavor poses a com
plex\, multiphysics problem involving modeling\, temporal and spatial disc
retization\, and software implementation considerations. This work focuses
on the time integration of the global atmosphere component\, with an emph
asis on the bulk atmosphere flow and cloud microphysics models. The nonhyd
rostatic bulk atmosphere flow models include acoustic waves that make the
overall system numerically stiff. Our work has developed a model formulati
on that is amenable to an IMEX approach\, where the acoustic waves are tre
ated implicitly. The performance of both existing and customized additive
Runge-Kutta methods is evaluated\, with certain methods remaining stable a
t the hydrostatic timestep. Cloud microphysics models currently use first-
order operator splitting to address the multiple timescales in the modeled
physics\, with at-best-first-order limiters required to keep quantities p
hysical. Our work has shown that higher-order explicit\, implicit\, and IM
EX Runge-Kutta methods with error-based adaptive timestep control are more
efficient for the subset of cloud microphysics considered thus far.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/61/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yiping Lu (Northwestern University)
DTSTART:20250527T161500Z
DTEND:20250527T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/62
DESCRIPTION:Title: Two Tales\, One Resolution: Physics-Informed Test
Time Scaling and Precondition\nby Yiping Lu (Northwestern University)
as part of Northwestern Applied Mathematics Seminar\n\nLecture held in M4
16 Tech Northwestern Evanston IL.\n\nAbstract\nIn this talk\, I will intro
duce a novel framework for physics-informed debiasing of machine learning
estimators\, which we call Simulation-Calibrated Scientific Machine Learni
ng (SCaSML). This approach leverages the structure of physical models to a
chieve two key objectives:\n\nUnbiased Predictions: It produces unbiased p
redictions even when the underlying machine learning predictor is biased.\
nOvercoming Dimensionality Challenges: It mitigates the curse of dimension
ality that often affects high-dimensional estimators.\n\nThe SCaSML paradi
gm integrates a (potentially) biased machine learning algorithm with a de-
biasing procedure that is rigorously designed using numerical analysis and
stochastic simulation. Our methodology aligns with recent advances in inf
erence-time computation—similar to those seen in the large language mode
l literature—demonstrating that additional computation can enhance ML es
timates.Furthermore\, we establish a surprising equivalence between our fr
amework and another research direction that utilizes approximate (lineariz
ed) solvers to precondition iterative methods. This connection not only br
idges two distinct areas of study but also offers new insights into improv
ing estimation accuracy in complex\, high-dimensional (PDE) settings.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/62/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Adrienne Fairhall (Reiss Lecture) (University of Washington)
DTSTART:20250513T161500Z
DTEND:20250513T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/63
DESCRIPTION:Title: Decoding Neurons to Behavior in a Model Organism<
/a>\nby Adrienne Fairhall (Reiss Lecture) (University of Washington) as pa
rt of Northwestern Applied Mathematics Seminar\n\nLecture held in M416 Tec
h Northwestern Evanston IL.\n\nAbstract\nThe freshwater cnidarian Hydra is
a fascinating model organism for neuroscience. It is transparent\; new ge
netic lines allow one to image activity in both neurons and muscle cells\;
it exhibits 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 mu
scle activity open the possibility of a complete model of neural control o
f behavior. We have developed a biophysical and biomechanical model of Hyd
ra's muscles and body that allows us to transform measured neural activity
into behavior. We also propose a model for how the neural network rebuild
s as the animal regenerates itself following bisection.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/63/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Johannes Schmidt-Hieber (University of Twente)
DTSTART:20250429T161500Z
DTEND:20250429T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/64
DESCRIPTION:Title: Understanding the Effect of GCN Convolutions in R
egression Tasks - NITMB Lecture\nby Johannes Schmidt-Hieber (Universit
y of Twente) as part of Northwestern Applied Mathematics Seminar\n\nLectur
e held in M416 Tech Northwestern Evanston IL.\n\nAbstract\n"Graph Convolut
ional Networks (GCNs) have become a pivotal method in machine learning for
modeling functions over graphs. Despite their widespread success across v
arious applications\, their statistical properties (e.g. consistency\, con
vergence rates) remain ill-characterized. To begin addressing this knowled
ge gap\, in this paper\, we provide a formal analysis of the impact of con
volution operators on regression tasks over homophilic networks. Focusing
on estimators based solely on neighborhood aggregation\, we examine how tw
o common convolutions - the original GCN and GraphSage convolutions - affe
ct the learning error as a function of the neighborhood topology and the n
umber of convolutional layers. We explicitly characterize the bias-varianc
e trade-off incurred by GCNs as a function of the neighborhood size and id
entify specific graph topologies where convolution operators are less effe
ctive. Our theoretical findings are corroborated by synthetic experiments\
, and provide a start to a deeper quantitative understanding of convolutio
nal effects in GCNs for offering rigorous guidelines for practitioners.\n
\nJoint work with Juntong Chen (Twente)\, Claire Donnat (U Chicago)\, and
Olga Klopp (ESSEC Business School\, Paris)"\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/64/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Adrienne Fairhall (Reiss Lecture) (University of Washington)
DTSTART:20250512T210000Z
DTEND:20250512T220000Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/65
DESCRIPTION:Title: In Search of Internal Mental Models\nby Adrie
nne Fairhall (Reiss Lecture) (University of Washington) as part of Northwe
stern Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwester
n Evanston IL.\n\nAbstract\nHow do we build the mental models that we use
to perceive\, navigate and reason about the world? How might these models
be inferred from neural activity? I will describe experiments and analysis
in collaboration with Beth Buffalo's lab to explore these questions in ou
r closest relatives\, nonhuman primates. In one example\, we compare monke
y and human behavior in a decision task\, and analyze how subjects make us
e of visual information and feedback to infer a hidden rule\, where the ru
le switches in an uncued fashion. We fit a suite of behavioral models and
learn that while humans are close to optimal Bayesian agents\, monkey beha
vior is better fit as reinforcement learning. This allows us to seek neura
l implementations of this internal belief update. Further\, while rodent h
ippocampus famously encodes the animal's spatial location\, we find eviden
ce that hippocampus in the primate serves a more cognitive role.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/65/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Niall Mangan (Northwestern University)
DTSTART:20251002T161500Z
DTEND:20251002T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/66
DESCRIPTION:Title: Data-driven model discovery meets mechanistic mod
eling for dynamical systems\nby Niall Mangan (Northwestern University)
as part of Northwestern Applied Mathematics Seminar\n\nLecture held in M4
16 Tech Northwestern Evanston IL.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/66/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Todd Gingrich (Northwestern University)
DTSTART:20251016T161500Z
DTEND:20251016T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/67
DESCRIPTION:Title: Tensor Networks for Stochastic Chemical Kinetics<
/a>\nby Todd Gingrich (Northwestern University) as part of Northwestern Ap
plied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evanst
on IL.\n\nAbstract\nChemical processes exhibit chaotic\, high-dimensional
dynamics as molecules undergo reactions and diffusion. In the special case
of a closed\, isolated system\, the complex dynamical processes relax int
o a comparatively 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 answ
er is to sample trajectories. In this talk\, I will discuss how the tensor
network techniques (DMRG & TDVP) from quantum many-body problems are natu
rally repurposed to study many-body stochastic chemical kinetics.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/67/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Meridith Joyce (University of Wyoming)
DTSTART:20251023T161500Z
DTEND:20251023T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/68
DESCRIPTION:Title: How to Find a Star by Accident\, or How Not to So
lve the "Great Dimming" of Betelgeuse\nby Meridith Joyce (University o
f Wyoming) as part of Northwestern Applied Mathematics Seminar\n\nLecture
held in M416 Tech Northwestern Evanston IL.\n\nAbstract\nAlpha Orionis\, p
opularly known as Betelgeuse\, is a nearby red supergiant star visible to
the naked eye. In light of the star's "Great Dimming"—a sudden\, extreme
drop in brightness that occurred in early 2020—a recent controversy sur
rounding Betelgeuse concerned whether it would explode as a supernova with
in the next few years\, centuries\, or millennia. Using a series of numeri
cal techniques including one-dimensional stellar evolution models\, hydrod
ynamic simulations\, linear oscillation calculations\, Fourier analysis\,
and the methods of a subfield of stellar astrophysics known as asteroseism
ology\, my collaborators and I constrained the timeline for Betelgeuse's d
emise and revised many of the best estimates for its fundamental propertie
s. In doing so\, we discovered not only that Betelgeuse was not likely to
undergo an imminent detonation\, but that a pulsation signal unexplained b
y our models was\, in fact\, the signature of an as-yet-undiscovered binar
y companion. Its presence was confirmed earlier this year. What we never m
anaged to do was explain the Great Dimming.\n\nIn this talk\, I will use t
he story of the discovery of Betelgeuse’s hidden\, low-mass binary compa
nion\, Alpha Orionis B—affectionately nicknamed “Betelbuddy”—both
to highlight the computational and numerical techniques employed in modern
stellar astrophysics and to illustrate how the most meaningful discoverie
s often arise not from confirming what we set out to find\, but from ventu
ring down the rabbit holes of unexpected problems that emerge along the wa
y.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/68/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Leonid Berlyand (The Pennsylvania State University)
DTSTART:20251106T171500Z
DTEND:20251106T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/69
DESCRIPTION:Title: Introduction to Mathematics of Artificial Neural
Networks (ANNs)\nby Leonid Berlyand (The Pennsylvania State University
) as part of Northwestern Applied Mathematics Seminar\n\nLecture held in M
416 Tech Northwestern Evanston IL.\n\nAbstract\nWe begin by addressing the
image classification problem\, where the goal is to map images x to class
es α using an exact classifier Φ(x\,α). Since an exact classifier is of
ten unfeasible\, Artificial Neural Networks (ANNs) F(x\,α) are used to ap
proximate Φ(x\,α)\, with α representing tunable parameters. Unlike clas
sical methods that use coefficients in expansions\, ANN parameters are ins
pired by the structure of the human brain. The process of optimizing these
parameters is called training.\n\nWe highlight two advancements: First\,
a pruning technique using the Marchenko-Pastur spectral approach from Rand
om Matrix Theory (RMT)\, which reduces computational complexity without sa
crificing accuracy. Second\, we examine autoencoders\, a special type of A
NN used for image-to-image transformations. The focus is on the fixed poin
ts of the autoencoder function F(x\,α)\, crucial for distinguishing real
images from fakes. Using the Banach Fixed Point Theorem\, we show that wit
h light-tailed distributions (e.g. Gaussian)\, there is a unique stable fi
xed point\, while with heavy-tailed distributions (e.g. Cauchy)\, there ar
e multiple fixed points N. The number of fixed points N depends non-monoto
nically on the number of layers L\, suggesting an optimal number of layers
L_0 for best performance. These results are vital for improving autoencod
er design.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/69/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nick Moore (Colgate University)
DTSTART:20251113T171500Z
DTEND:20251113T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/70
DESCRIPTION:Title: Reversals of the Large-scale Circulation in Therm
al Convection\nby Nick Moore (Colgate University) as part of Northwest
ern Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern
Evanston IL.\n\nAbstract\nThermal convection\, or the tendency of heat to
rise and cool material to descend\, often gives rise to a large-scale circ
ulatory flow structure. It is known that the large-scale circulation (LSC)
can undergo spontaneous reversals. In the atmosphere\, reversals can resu
lt in a sudden change in wind direction\, while in Earth’s liquid core\,
reversals may play a role in magnetic dipole shifts. I will discuss LSC r
eversals in the context of 2D annular thermal convection. Through comparis
on with direct numerical simulations\, I’ll show that a low-dimensional
dynamical system derived systematically from Galerkin truncation of the go
verning equations accurately describes a sequence of parameter bifurcation
s\, including the onset of circulatory flow\, the appearance of chaotic LS
C reversals\, and finally a high-Rayleigh-number state of periodic LSC rev
ersals with small-scale turbulence. When cast in terms of the fluid’s an
gular momentum and center of mass\, the model reveals equivalence to a pen
dulum system with driving term that raises the center of mass above the fu
lcrum. It is the competition between driving\, restoring\, and damping tha
t leads to the range of convective states. This physical picture yields ac
curate predictions for the frequency of regular LSC reversals in the high
Rayleigh-number limit and offers a transparent mechanism for reversals. I
will briefly discuss extensions of the model\, including one that accurate
ly recovers the gross heat transport.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/70/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ed Lyman (University of Delaware)
DTSTART:20251120T171500Z
DTEND:20251120T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/71
DESCRIPTION:Title: Elastic and Dynamic Response of Membranes Across
Scales\nby Ed Lyman (University of Delaware) as part of Northwestern A
pplied Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evans
ton IL.\n\nAbstract\nCell membranes are quasi-2D soft materials\, about 5
nm thick but with hundreds of square microns of surface area. They are a b
ilayer structure\, assembled from amphiphilic molecules (lipids) and prote
ins. The function of membranes imposes challenging design constraints: imp
ermeable yet fluid\, mechanically robust yet deformable. Across the tree o
f life\, cells meet these challenges by synthesizing a diverse array of li
pids\, whose chemistry and interactions determine the key continuum proper
ties\, like stiffness against bending and the viscosity which controls dif
fusion and encounter of membrane bound signaling partners. In this talk I
will present our group's work using simulations to connect lipid chemistry
and membrane properties\, focusing on two applications. The first project
considers the membranes of a family of marine invertebrates called ctenop
hores\, which synthesize a specialized lipid chemistry to maintain membran
e deformability at high pressure. The second project focuses on how lipid
chemistry is used to control the viscosity of the membrane\, and the chall
enges that come with trying to measure the viscosity of soft\, thin\, not-
quite two dimensional fluids.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/71/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mike Shelley (Flatiron Institute)
DTSTART:20251027T161500Z
DTEND:20251027T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/72
DESCRIPTION:Title: Self-Organization\, Flows\, and Transport in (and
of) Living Cells\nby Mike Shelley (Flatiron Institute) as part of Nor
thwestern Applied Mathematics Seminar\n\nLecture held in M416 Tech Northwe
stern Evanston IL.\n\nAbstract\nOrganisms organize their internal contents
at the microscale through striking dynamical processes. In the early C. e
legans embryo\, pronuclei are positioned by the interplay of centrosomal a
rrays and molecular motors as the cell prepares for its first division. In
female Drosophila\, self-organized intracellular flows transport material
s across growing egg cells\, establishing functional asymmetries essential
for development. And in males\, ultralong sperm - as long as the organism
itself - are packed and stored in a remarkable state of ordered unrest.\n
\nI will describe our work at Flatiron in understanding these phenomena by
tightly interfacing multiscale modeling and simulation with quantitative
experiment. The theoretical frameworks draw on fluid and nonlinear dynamic
s\, coarse-graining\, and active matter\, and show how applied mathematics
can illuminate the biophysical mechanisms that enable living systems to b
uild\, move\, and organize themselves.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/72/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Roberto Zenit (Brown University)
DTSTART:20260212T171500Z
DTEND:20260212T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/73
DESCRIPTION:Title: The Fluid Mechanics of Splatter Painting\nby
Roberto Zenit (Brown University) as part of Northwestern Applied Mathemati
cs Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\n\nAbstr
act\nIn splat painting\, a collection of liquid droplets is projected onto
the substrate by imposing a controlled acceleration to a paint-loaded bru
sh.\n\nTo unravel the physical phenomena at play in this artistic techniqu
e\, we perform experiments where the amount of expelled liquid is characte
rized function of the liquid viscosity\, brush properties and imposed acce
leration. Experimental trends are rationalized by simple physical models\,
revealing the existence of an inertia-dominated flow in the anisotropic\,
porous tip of the brush. We argue that splat painting artists intuitively
tune their technique to work in this regime\, which may also play a role
in other pulsed flows\, like fabric drying\, violent expiratory events or
sudden geophysical processes.\n
LOCATION:https://stable.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:20260404T110656Z
UID:Modeling_and_Computation/74
DESCRIPTION:Title: Collective Social Dynamics Through the Lens of St
atistical Physics\nby Chaoming Song (University of Miami (sabbatical a
t Northwestern University)) as part of Northwestern Applied Mathematics Se
minar\n\nLecture held in M416 Tech Northwestern Evanston IL.\n\nAbstract\n
Social dynamics emerge from the complex interactions among large groups of
individuals. Despite their diversity\, many social systems exhibit compar
able collective behaviors\, ranging from sudden shifts in group states to
gradual diffusion and spreading processes\, analogous to those found in ph
ysical systems. These shared patterns provide unique opportunities to appl
y the tools and principles of statistical physics\, including phase transi
tions\, critical phenomena\, self-organization\, and non-equilibrium proce
sses\, to uncover the fundamental mechanisms driving large-scale social ph
enomena. In this talk\, I will present case studies illustrating complex h
uman behaviors across multiple social systems\, addressing topics such as
opinion polarization\, social unrest\, and the diffusion of scientific inn
ovation. We conclude with an exploration of social interactions among chil
dren in classroom environments\, revealing an analogy in which coexistence
phases\, similar to those observed in multiphase liquid systems\, can als
o emerge in social contexts.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/74/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Melanie Mitchell (Santa Fe Institute)
DTSTART:20260514T161500Z
DTEND:20260514T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/76
DESCRIPTION:Title: Reiss Lecture\nby Melanie Mitchell (Santa Fe
Institute) as part of Northwestern Applied Mathematics Seminar\n\nLecture
held in M416 Tech Northwestern Evanston IL.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/76/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ching-Yao Lai (Stanford University)
DTSTART:20260129T171500Z
DTEND:20260129T181500Z
DTSTAMP:20260404T110656Z
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://stable.researchseminars.org/talk/Modeling_and_Computation
/77/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rich Townsend (University of Wisconsin)
DTSTART:20260205T171500Z
DTEND:20260205T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/78
DESCRIPTION:Title: Numerical Asteroseismology with the GYRE Code
\nby Rich Townsend (University of Wisconsin) as part of Northwestern Appli
ed Mathematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston
IL.\n\nAbstract\nSome stars display periodic fluctuations in their brightn
ess\, arising from the excitation of their global oscillation modes. By mo
deling these fluctuations\, we can place remarkably narrow constraints on
the stars' global properties and detailed internal structure—a technique
known as "asteroseismology".\n\nIn this talk I'll review the theoretical
principles of asteroseismology\, and describe their implementation in GYRE
—an open-source code I've been developing for a little over a decade. De
spite committing a fair number of computational cardinal sins\, GYRE appea
rs to be accurate\, robust\, and fast\, and has been adopted by many group
s around the world as their workhorse for numerical asteroseismology. I'll
showcase a few GYRE-based projects that I've recently been involved in\,
and then discuss enhancements that enable GYRE to simulate tidal phenomena
in binary-star and star-planet systems.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/78/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Stefano Allesina (University of Chicago)
DTSTART:20260226T171500Z
DTEND:20260226T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/79
DESCRIPTION:Title: Global stability of ecological and evolutionary d
ynamics via equivalence\nby Stefano Allesina (University of Chicago) a
s part of Northwestern Applied Mathematics Seminar\n\nLecture held in M416
Tech Northwestern Evanston IL.\n\nAbstract\nThe replicator and the Genera
lized Lotka-Volterra equations are closely-related\, foundational models i
n evolutionary game theory and community ecology\, respectively. The conce
pt of evolutionary stability and its relationship with dynamic stability h
as received significant attention: in the replicator equation\, a mixed ev
olutionary stable strategy is also dynamically globally stable—i.e.\, wi
ll be reached by any trajectory originating from positive conditions. Intr
iguingly\, the converse is not true: there are replicator equations yieldi
ng dynamically stable mixed strategies that are not evolutionary stable. H
ere we consider two classes of equivalence (i.e.\, transformations that do
not alter the qualitative dynamics) for the replicator equation\, to dete
rmine whether a globally-stable\, but not evolutionary stable strategy map
s into an equivalent state that is evolutionary stable—and show that thi
s is the case for the examples that have been put forward so far. We deriv
e the same two classes of equivalence for the Generalized Lotka-Volterra m
odel\, obtaining the same conditions for stability as for the replicator e
quation\, and show that in this way we can characterize stability when oth
er methods fail. By unifying the approach to proving stability for the rep
licator equation and Lotka-Volterra models\, we bring these foundational e
quations even closer together.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/79/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Xiao Yu Wang (CRI Foundation)
DTSTART:20260312T161500Z
DTEND:20260312T171500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/80
DESCRIPTION:Title: What the proposed credit card regulation really m
eans for consumers\nby Xiao Yu Wang (CRI Foundation) as part of Northw
estern Applied Mathematics Seminar\n\nLecture held in M416 Tech Northweste
rn Evanston IL.\n\nAbstract\nMy work addresses the need for a theoretical
framework to evaluate proposed caps on credit card interest rates and swip
e fees by developing a dynamic model that produces usable insights into th
e patterns and interdependence of consumer spending\, credit use\, and rep
ayment choices\, merchant pricing and competition\, and the contract decis
ions of card issuers. There are several key innovations. First\, I derive
conditions under which credit cards increase total spending instead of sim
ply reallocating it (rather than assuming one or the other). This is criti
cal since credit cards are a special type of two-sided platform: the lendi
ng aspect 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 merch
ant pricing and entry\, rather than assuming fixed merchants or that deman
d and elasticities for goods purchased with credit cards are invariant in
consumer wealth. Third\, I study which consumers fall into repayment traps
and why. Preliminary results identify overlooked mechanisms and externali
ties which have important implications for the total and distributional im
pact of rate caps\, fee caps\, and increased competition\, and for optimal
regulation of credit cards in general.\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/80/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Xiangyi Meng (Rensselaer Polytechnic Institute)
DTSTART:20260305T171500Z
DTEND:20260305T181500Z
DTSTAMP:20260404T110656Z
UID:Modeling_and_Computation/82
DESCRIPTION:Title: The shape of physical networks\nby Xiangyi Me
ng (Rensselaer Polytechnic Institute) as part of Northwestern Applied Math
ematics Seminar\n\nLecture held in M416 Tech Northwestern Evanston IL.\n\n
Abstract\nThe brain’s connectome and the vascular system are examples of
physical networks—tangible\, web-like objects that exist in real space
(not just in our papers). This physical reality means these networks combi
ne a graph structure\, describing their topological connectivity\, with a
physical structure\, capturing the shape of all nodes and links. How do we
best describe this physical structure? Naturally\, we model it as a geome
tric object\, i.e.\, a manifold embedded in 3D space. To do this\, we turn
to an unexpected mathematical tool: the framework of covariant closed str
ing field theory\, developed in the 1980s. This framework provides an exac
t correspondence between network-like graphs and smooth surfaces. We show
that\, as interpreted by this string-theoretical framework\, geometric obj
ects acquire network shapes precisely because they tend to minimize their
surface areas. We developed both a Riemann surface formulation and a numer
ical algorithm to simulate this minimization process\, finding that it pre
dicts structural features challenging traditional explanations of network
formation. Specifically\, this minimization predicts the emergence of trif
urcations and branching angles that\, while defying conventional models su
ch as Steiner graphs\, are in excellent agreement with the local tree-like
organization of physical networks across diverse domains\, from human neu
rons to corals. We conclude by discussing potential applications of this f
undamental discovery\, from interpreting structural changes in neurologica
l disorders to designing novel metamaterials. \n\n(A popular summary of th
e work can be found at: Finally A Use for String Theory! https://www.youtu
be.com/watch?v=Hj5b0ieVWSo )\n
LOCATION:https://stable.researchseminars.org/talk/Modeling_and_Computation
/82/
END:VEVENT
END:VCALENDAR