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• Apr

  1

  Appl Math: Yiping Lu on "Two Tales, One Resolution: Physics-Informed Test Time Scaling and Precondition"

  McCormick-Engineering Sciences and Applied Mathematics (ESAM)

  11:15 AM M416, Technological Institute

  EVENT DETAILS

  Title: Two Tales, One Resolution: Physics-Informed Test Time Scaling and Precondition

  Speaker: Yiping Lu, Northwestern University

  Abstract: In this talk, I will introduce a novel framework for physics-informed debiasing of machine learning estimators, which we call Simulation-Calibrated Scientific Machine Learning (SCaSML). This approach leverages the structure of physical models to achieve two key objectives:

  Unbiased Predictions: It produces unbiased predictions even when the underlying machine learning predictor is biased.
  Overcoming Dimensionality Challenges: It mitigates the curse of dimensionality that often affects high-dimensional estimators.

  The SCaSML paradigm 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 inference-time computation—similar to those seen in the large language model literature—demonstrating that additional computation can enhance ML estimates. Furthermore, we establish a surprising equivalence between our framework and another research direction that utilizes approximate (linearized) solvers to precondition iterative methods. This connection not only bridges two distinct areas of study but also offers new insights into improving estimation accuracy in complex, high-dimensional (PDE) settings.

  Zoom: https://northwestern.zoom.us/j/94570889326

  -----

  To subscribe to the Applied Mathematics Colloquia List send a message to LISTSERV@LISTSERV.IT.NORTHWESTERN.EDU with the command:

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  more less

  TIME Tuesday, April 1, 2025 at 11:15 AM - 12:15 PM

  LOCATION M416, Technological Institute    map it

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  CONTACT Ted Shaeffer    ted.shaeffer@northwestern.edu EMAIL

  CALENDAR McCormick-Engineering Sciences and Applied Mathematics (ESAM)

• Mar

  17

  Winter exams begin

  University Academic Calendar

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  Winter exams begin

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  TIME Monday, March 17, 2025

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  CONTACT Office of the Registrar    nu-registrar@northwestern.edu EMAIL

  CALENDAR University Academic Calendar

• Mar

  22

  Spring Break Begins

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  Spring Break Begins

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  TIME Saturday, March 22, 2025

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  CONTACT Office of the Registrar    nu-registrar@northwestern.edu EMAIL

  CALENDAR University Academic Calendar

• Mar

  31

  Spring Break Ends

  University Academic Calendar

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  Spring Break Ends

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  TIME Monday, March 31, 2025

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  CONTACT Office of the Registrar    nu-registrar@northwestern.edu EMAIL

  CALENDAR University Academic Calendar

• Apr

  1

  Spring Classes Begin - Northwestern Monday: Classes scheduled to meet on Mondays meet on this day.

  University Academic Calendar

  All Day

  EVENT DETAILS

  Spring Classes Begin - Northwestern Monday: Classes scheduled to meet on Mondays meet on this day.

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  TIME Tuesday, April 1, 2025

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  CONTACT Office of the Registrar    nu-registrar@northwestern.edu EMAIL

  CALENDAR University Academic Calendar

• Apr

  8

  Appl Math: Brennan Sprinkle on "The Countoscope: Counting Particles to Measure Dynamic Properties of Suspensions In and Out of Equilibrium"

  McCormick-Engineering Sciences and Applied Mathematics (ESAM)

  11:15 AM M416, Technological Institute

  EVENT DETAILS

  Title: The Countoscope: Counting Particles to Measure Dynamic Properties of Suspensions In and Out of Equilibrium

  Speaker: Brennan Sprinkle, Colorado School of Mines

  Abstract: Modern microscopy techniques can image complex, microscopic systems with an unprecedented resolution – but methods to analyze these images are much less robust. Available techniques to probe dynamics rely on reconstructing particle trajectories, which can be difficult or impossible in some cases, or some form of video analysis, which can be unreliable and 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 different measures of correlation between these observation boxes, we can `zoom’ in or out to measure individual or collective particle kinetics in both passive and active systems. Using colloidal suspensions as a test case, we employ a combination of experiments, simulations, and analytical theory to support our findings.

  Zoom: https://northwestern.zoom.us/j/97359869177

  -----

  To subscribe to the Applied Mathematics Colloquia List send a message to LISTSERV@LISTSERV.IT.NORTHWESTERN.EDU with the command:

  add esam-seminar Youremail Firstname Lastname

  more less

  TIME Tuesday, April 8, 2025 at 11:15 AM - 12:15 PM

  LOCATION M416, Technological Institute    map it

  ADD TO CALENDAR

  CONTACT Ted Shaeffer    ted.shaeffer@northwestern.edu EMAIL

  CALENDAR McCormick-Engineering Sciences and Applied Mathematics (ESAM)

• Apr

  15

  Appl Math: Dan Wilson on "Phase-Amplitude-Based Techniques for Control and Analysis of Strongly Perturbed Limit Cycle Oscillators"

  McCormick-Engineering Sciences and Applied Mathematics (ESAM)

  11:15 AM M416, Technological Institute

  EVENT DETAILS

  Title: Phase-Amplitude-Based Techniques for Control and Analysis of Strongly Perturbed Limit Cycle Oscillators

  Speaker: Dan Wilson, University of Tennessee, Knoxville

  Abstract: While phase-based reduction techniques have a rich history in the analysis and control of oscillatory dynamical systems, the overwhelming majority of theoretical analysis in this field has been performed in the weakly 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 when considering strong perturbations. In this presentation, I will discuss the use of isostable coordinates, which characterize level sets of the slowest decaying eigenmodes of the Koopman operator in conjunction with phase-based techniques to yield analytically tractable reduced order models that are valid in the strongly perturbed regime. Applications involving phase resetting of circadian rhythms following rapid travel across multiple time zones illustrate the utility of these new methods in situations where standard, phase-only techniques fail. I will also discuss related work motivated by experimental and detailed computational studies finding that coupled circadian oscillators with decreased levels of synchronization are able to more rapidly adjust to changes in circadian time. Theoretical 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 synchronization and phase resetting efficiency. In the context of jet-lag recovery strategies, further analysis reveals that transient desynchronization facilitates phase resetting when the relaxation rate of the population limit cycle is sufficiently slow relative to the natural frequency of the population oscillation.

  Zoom: https://northwestern.zoom.us/j/91324444590

  -----

  To subscribe to the Applied Mathematics Colloquia List send a message to LISTSERV@LISTSERV.IT.NORTHWESTERN.EDU with the command:

  add esam-seminar Youremail Firstname Lastname

  more less

  TIME Tuesday, April 15, 2025 at 11:15 AM - 12:15 PM

  LOCATION M416, Technological Institute    map it

  ADD TO CALENDAR

  CONTACT Ted Shaeffer    ted.shaeffer@northwestern.edu EMAIL

  CALENDAR McCormick-Engineering Sciences and Applied Mathematics (ESAM)