Past Events

Hao Jia (University of Minnesota, Twin Cities)

In this sequence of lectures, we will introduce the classical stability problem for incompressible Euler and Navier Stokes equations. We will focus on the specific setting of the perturbative regime near a spectrally stable monotonic shear flow, and explain various dynamical phenomena, such as inviscid damping for the Euler equation and enhanced dissipation for the Navier Stokes equations in the high Reynolds number regime. Recent advances and further open problems will also be discussed if time permits.

Gong Chen (Georgia Institute of Technology)

In these lectures, I will introduce the spectral theory and the scattering theory associated with the 1d Schr\”odinger operator. Then I will illustrate how these tools can be used to understand and compute the large-time behaviors of nonlinear dispersive equations.

Jiajie Chen (California Institute of Technology)

Whether the 3D incompressible Euler equations can develop a finite-time singularity from smooth initial data is an outstanding open problem. In these lectures, we will describe some recent progress on singularity formation in incompressible fluids and related models. We will begin with some properties of the 3D Euler equations useful for studying singularity formation and the dynamic rescaling formulation of the 3D Euler equations. Then we will discuss some ideas to overcome some difficulties in singularity formation and study finite time blowup based on the stability of an approximate blowup profile. We will compare this stability and another notion of stability of blowup. Lastly, we will discuss some ideas for constructing finite time blowup from smooth initial data, particularly in 1D models of the Euler equations, which can be helpful in studying the singularity formation of 3D Euler with smooth data.

Dallas Albritton (Princeton University)

It is not yet known whether Navier-Stokes solutions develop singularities in finite time. If they do, then the solutions can be continued beyond the singularities as Leray-Hopf solutions. It is therefore a fundamental question, Are Leray-Hopf solutions unique? The goal of this course is to present very recent developments in our understanding of this question.

We will begin by quickly reviewing the Navier-Stokes basics: dimensional analysis, the energy balance, pressure, weak solutions, perturbation theory, and weak-strong uniqueness. To save time, we will not present the complete proofs.

Next, we will explain aspects of the Jia, Sverak, and Guillod program (Jia-Sverak, Inventiones 2014, JFA 2015; Guillod-Sverak, arXiv 2017) and, in particular, how instability in self-similarity variables can generate non-uniqueness. We will briefly discuss bifurcations, stable and unstable manifolds, and, time permitting, a short proof of the existence of large self-similar solutions.

Finally, we will present the recent work (A.-Brue-Colombo, Ann. Math. 2022) which rigorously established non-uniqueness of Leray-Hopf solutions with forcing. We will present the main idea but focus on the spectral perturbation arguments.

No prior knowledge of the Navier-Stokes equations is required, though it might be beneficial to preview background on weak and mild solutions in, for example, Chapters 4 and 11 in Robinson-Rodrigo-Sadowski or Chapters 3 and 5 in Tsai.

Hao Jia (University of Minnesota, Twin Cities)

In this sequence of lectures, we will introduce the classical stability problem for incompressible Euler and Navier Stokes equations. We will focus on the specific setting of the perturbative regime near a spectrally stable monotonic shear flow, and explain various dynamical phenomena, such as inviscid damping for the Euler equation and enhanced dissipation for the Navier Stokes equations in the high Reynolds number regime. Recent advances and further open problems will also be discussed if time permits.

Gong Chen (Georgia Institute of Technology)

In these lectures, I will introduce the spectral theory and the scattering theory associated with the 1d Schr\”odinger operator. Then I will illustrate how these tools can be used to understand and compute the large-time behaviors of nonlinear dispersive equations.

Jiajie Chen (California Institute of Technology)

Whether the 3D incompressible Euler equations can develop a finite-time singularity from smooth initial data is an outstanding open problem. In these lectures, we will describe some recent progress on singularity formation in incompressible fluids and related models. We will begin with some properties of the 3D Euler equations useful for studying singularity formation and the dynamic rescaling formulation of the 3D Euler equations. Then we will discuss some ideas to overcome some difficulties in singularity formation and study finite time blowup based on the stability of an approximate blowup profile. We will compare this stability and another notion of stability of blowup. Lastly, we will discuss some ideas for constructing finite time blowup from smooth initial data, particularly in 1D models of the Euler equations, which can be helpful in studying the singularity formation of 3D Euler with smooth data.

Dallas Albritton (Princeton University)

It is not yet known whether Navier-Stokes solutions develop singularities in finite time. If they do, then the solutions can be continued beyond the singularities as Leray-Hopf solutions. It is therefore a fundamental question, Are Leray-Hopf solutions unique? The goal of this course is to present very recent developments in our understanding of this question.

We will begin by quickly reviewing the Navier-Stokes basics: dimensional analysis, the energy balance, pressure, weak solutions, perturbation theory, and weak-strong uniqueness. To save time, we will not present the complete proofs.

Next, we will explain aspects of the Jia, Sverak, and Guillod program (Jia-Sverak, Inventiones 2014, JFA 2015; Guillod-Sverak, arXiv 2017) and, in particular, how instability in self-similarity variables can generate non-uniqueness. We will briefly discuss bifurcations, stable and unstable manifolds, and, time permitting, a short proof of the existence of large self-similar solutions.

Finally, we will present the recent work (A.-Brue-Colombo, Ann. Math. 2022) which rigorously established non-uniqueness of Leray-Hopf solutions with forcing. We will present the main idea but focus on the spectral perturbation arguments.

No prior knowledge of the Navier-Stokes equations is required, though it might be beneficial to preview background on weak and mild solutions in, for example, Chapters 4 and 11 in Robinson-Rodrigo-Sadowski or Chapters 3 and 5 in Tsai.

Advisory: 
Note that the workshop is intended for graduate students and advanced undergraduates.

Organizers: 

• Hao Jia, University of Minnesota, Twin Cities

In this five-day workshop for both graduate students and advanced undergraduate students, there will be a number of lectures given by active and leading experts in several important areas of analysis of partial differential equations, especially those arising from mathematical analysis of fluid dynamics and nonlinear waves. Participants will learn about the physical background, rigorous mathematical formulation, analytic tools, and latest developments in important PDE phenomena including singularity formation, uniqueness and non-uniqueness of weak solutions, stability mechanisms, and soliton resolution. Participants will also have many opportunities to interact with the lecturers in informal settings.

We will provide financial support to facilitate students' participation. To apply, please submit the following documents through the Workshop Application link at the top of the page:

1. A brief CV or resume.  (A list of publications is not necessary.);
2. A reference letter from your advisor or professor.

Supported by NSF CAREER 1945179

Schedule

Subscribe to this event's calendar

Monday, July 25, 2022

Tuesday, July 26, 2022

Wednesday, July 27, 2022

Thursday, July 28, 2022

Friday, July 29, 2022

Participants

Advisory: The deadline for application is March 18, 2022.

Organizers

• Ashlee Ford Versypt — University at Buffalo (SUNY)
• Rebecca Segal — Virginia Commonwealth University
• Blerta Shtylla — Pfizer
• Suzanne Sindi — University of California, Merced

This five-day workshop focuses on collaborative research, in small groups of women, each group working on an open problem in a particular area of mathematical biology. Each group will include women at different career stages, from early career mathematicians to leaders in the field, to bolster leadership among senior mathematical biologists and data scientists, and to provide mentoring for early career mathematicians. Complementing the research time there will be activities engaging all participants, including career panels, discussions and building community.

Women researchers from underrepresented groups, working at universities with a teaching focus and small colleges, and those isolated geographically from potential collaborators, are especially encouraged to apply. 

Schedule

Monday, June 20, 2022

• 8:30–9:30am — Workshop Check-in (UnitedHealth Group-Minnetonka)
• 9:30am–12:00pm — Intro and Project Overviews
• 12–12:30pm — Quick Group Meeting
• 12:30–1:30 pm — Lunch (on site)
• 1:30–5pm — Group Research
• 5–7pm — Group Research

Tuesday, June 21, 2022

• 9am–12pm — Research
• 12–1pm — Lunch
• 1–2:30pm — Career Panel
• 2:30–5:30pm — Research

Wednesday, June 22, 2022

• 9am–12pm — Research
• 12pm–1pm — Lunch
• 1–2pm — Pair and Share
• 2–5:30pm — Research

Thursday, June 23, 2022

• 9am–12pm — Research
• 12–1pm — Lunch
• 1–5:30pm — Research

Friday, June 24, 2022

• 8:30–11:30am — Project Presentations / Wrap-up

Participants

Projects and teams

Project 1: HIV, Pre-exposure prophylaxis, and drug resistance

• Katharine Gurski, Howard University
• Yeona Kang, Howard University

In December 2021, the FDA approved an injectable pre-exposure prophylaxis (PrEP) for use in at-risk adults and adolescents to reduce the risk of sexually acquired HIV.  The cabotegravir extended-release injectable suspension is given first as two initiation injections administered one month apart, and then every two months thereafter. In this project, we aim to study how dynamics of drug-sensitive and drug-resistant HIV strains within hosts affect the prevalence of drug-resistant strains in the population when injectable pre-exposure prophylaxis enters the picture.  This project will use methods from dynamical systems, statistics as it relates to sensitivity analysis, data, and parameter estimation and numerical simulation.

Project 2: Modeling the stability and effectiveness of dosing regimens of oral hormonal contraceptives

• Mentor Lisette de Pillis, Harvey Mudd College
• Heather Zinn Brooks, Harvey Mudd College

Oral contraceptives are a leading form of birth control in the United States, but consistent daily use and unwanted side effects can pose challenges for some users. Existing mathematical models of the effects of hormonal contraception on the menstrual cycle do not incorporate the dynamics of the on/off dosing regimens or the metabolism of the exogenous hormones, although methods from differential equations and dynamical systems are well-positioned to investigate these questions. We aim to explore the stability of the contraceptive state achieved by oral hormonal contraceptives using a mechanistic mathematical model of the menstrual cycle. Such a model could provide insight into when a contraceptive state is lost due to inconsistency or changes in hormonal birth control use, which may further inform the advisement of care providers and the choices of birth control users.

Project 3: Effects of exogenous-hormone induced perturbations on blood clotting

• Mentor Karin Leiderman, Colorado School of Mines
• Anna Nelson, Duke University

Exogenous hormones are used by hundreds of millions of people worldwide for contraceptives and hormonal replacement therapy (HRT). However, estrogen in combined oral contraceptives (OC) and HRT have been shown to significantly increase the risk of both arterial and venous thrombosis.The objectives for this project are to use a mechanistic mathematical model of flow-mediated coagulation to investigate the effects of exogenous-hormone induced perturbations that have been observed on blood clotting. We will use the model to simulate specified hormone induced perturbation profiles, i.e., percent changes in plasma levels of proteins and blood platelets caused by estrogen and progesterone, in varying doses, separately and together. The first objective will be to verify the observations from the literature showing increased clotting for specified profiles and doses. It is also well known that plasma levels of clotting factors vary among individuals. Variation that is considered normal and still healthy is a range between 50 and 150% of the mean value of the healthy population. Our second objective will be to identify individuals that may be more susceptible to thrombosis due to certain hormones and doses. We will accomplish this by performing global sensitivity analysis on model output metrics where variance is due to uncertainty in the input levels of clotting factors, platelets, and hormones. 

Project 4: Development of effective therapeutic schedules in breast and gynecological cancers

• Morgan Craig, University of Montreal
• Adrianne Jenner, Queensland University of Technology

After lung cancer, breast cancer continues to be projected as the second most commonly diagnosed cancer in Canada. Leveraging data cancer growth, pharmacokinetic and pharmacodynamic models of various cancer therapies, and models of therapeutic resistance, this project aims to identify responders/non-responders to treatments and establish effective therapeutic schedules in breast and gynecological cancers. For this, we will develop mathematical and pharmacokinetic/pharmacodynamic models, integrated with patient data, to construct and implement in silico clinical trials. Familiarity with MATLAB, Python, and/or R is recommended. Other data fitting software including Monolix may be introduced, but prior knowledge is not necessary.

Project 5: Modeling neonatal respiratory distress

• Laura Ellwein Fix, Virginia Commonwealth University
• Sharon Lubkin, North Carolina State University

Respiratory distress in the newborn, a condition characterized by difficulty breathing, occurs in about 7% of newborns. This team’s project will address a question related to modeling of respiratory mechanics in the neonatal population. We previously developed an ordinary differential equations (ODE) model describing dynamic breathing volumes and pressures in aggregate compartments depicting the airways, lungs, chest wall, and intrapleural space, in an ideal spontaneously breathing preterm infant. Current areas of inquiry include application to ventilated infants and parameter identification using clinical data from a neonatal intensive care unit or an animal model. Alternatively, a specific unsolved problem could arise that requires the incorporation of a different dynamic model type such as spatially dependent or stochastic, or connects the organ level respiratory system with different physiology. The team’s co-leaders have interests in physiology, biotransport, tissues, cardiovascular and respiratory systems, and the use of noninvasive data in modeling. Our expertise centers on physiological mechanistic modeling, spatiotemporal systems and dynamics, parameter identification, numerics, and model development starting from simple to complex. Ideal team members would have interest and knowledge in some of these areas and embrace the opportunity to learn in other areas.

Project 6: On stable estimation of disease parameters and forecasting in epidemiology

• Ruiyan Luo, Georgia State University
• Alexandra Smirnova, Georgia State University

Real-time reconstruction of disease parameters for an emerging outbreak helps to provide crucial information for the design of public health policies and control measures. The goal of our team project is to investigate and compare parameter estimation algorithms that do not require an explicit deterministic or stochastic trajectory of system evolution, and where the state variable(s) and the unknown disease parameters are reconstructed in a predictor-corrector manner in order to mitigate the excessive computational cost of a quasi-Newton step. We plan to look at uncertainty quantification and implications of parameter estimation on forecasting of future incidence cases. Theoretical study will be combined with numerical experiments using synthetic and real data for COVID-19 pandemic.