My name is Sean Reiter. I am a Courant Instructor with the Courant Institute of Mathematical Sciences, New York University. There, I am working in the research group of Dr. Benjamin Peherstorfer.
Prior to moving to New York University, I obtained my doctoral degree in mathematics from Virginia Tech in Blacksburg, Virginia, under the supervision of Dr. Mark Embree and Dr. Serkan Gugercin.
I am an applied mathematician. My research focuses on theoretical and computational aspects of numerical method development for large-scale and structured dynamical systems. Dynamical systems are mathematical models of real-world phenomena that change their behavior over time. They are widely used as computational tools for understanding and making reliable predictions about physical systems.
To capture the underlying behavior accurately, such models are often large, requiring many degrees of freedom and becoming expensive to evaluate. Much of my work concerns system approximation, or model reduction: replacing a large-scale, expensive-to-evaluate system with a smaller, cheaper-to-evaluate surrogate that faithfully reproduces the behavior of the original. This is possible because such systems, despite their size, frequently evolve along low-dimensional structures that can be identified and exploited. Related threads of my work address data-driven modeling — the construction of surrogate models directly from measured data — and state estimation, the problem of reconstructing a system's internal state from limited observations. I am interested in classical approaches to these problems, grounded in systems and control theory, as well as those based on modern machine learning tools. The input-to-output frequency response of numerous types of dynamical systems can be understood through rational functions. To this end, I am interested in computational methods for rational function approximation, with a specific focus on algorithms for best $\mathcal{L}_{2}$ approximation.
The central themes of my research are systems and control theory, numerical linear algebra, approximation theory, and scientific machine learning.
I am also committed to reproducibility in the computational sciences. Each of my written works below is accompanied by a link to a supplementary software package containing the code and data that can be used to reproduce the results in the accompanying manuscript.
Professional Experience
| Courant Instructor Courant Institute of Mathematical Sciences, New York University | New York, NY August 2025 – Present |
| Graduate Research and Teaching Assistant Department of Mathematics, Virginia Tech | Blacksburg, VA January 2019 – May 2025 |
| Givens Associate MCS Division, Argonne National Laboratory | Lemont, IL June – August 2022, 2023 |
Education
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Ph.D. in Mathematics
Virginia Tech
Advised by Dr. Mark Embree and Dr. Serkan Gugercin Dissertation: Dimension Reduction in Structured Dynamical Systems: Optimal-$\mathcal{H}_{2}$ Approximation, Data-Driven Balancing, and Real-Time Monitoring. |
Blacksburg, VA May 2025 |
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M.S. in Mathematics
Virginia Tech
Advised by Dr. Mark Embree and Dr. Serkan Gugercin Thesis: On the Tightness of the Balanced Truncation Error Bound with an Application to Arrowhead Systems |
Blacksburg, VA December 2021 |
| B.S. in Mathematics Virginia Tech In Honors, Minor in Chemistry, Summa Cum Laude | Blacksburg, VA May 2018 |
I have a strong commitment to mathematics education at both the undergraduate and graduate levels. My teaching statement (as of August 2025) describes my philosophy and approach in detail.
| Instructor of Record MATH-UA 4424: Numerical Analysis | New York University, New York NY Spring 2026 |
| Instructor of Record MATH-UA 352: Numerical Analysis | New York University, New York NY Fall 2025 |
| Graduate Teaching Assistant MATH 4864: Computational Modeling and Data Analytics Capstone | Virginia Tech, Blacksburg VA Fall 2024 |
| Graduate Instructor of Record MATH 2534: Intro to Discrete Math | Virginia Tech, Blacksburg VA Fall 2023 |
| Graduate Instructor of Record CMDA 1634: Discovering Computational Modeling and Data Analytics | Virginia Tech, Blacksburg VA Fall 2022 |
| Graduate Instructor of Record MATH 1225: Calculus of a Single Variable | Virginia Tech, Blacksburg VA Fall 2021 |
| Graduate Teaching Assistant CMDA 1984: First-year Experience | Virginia Tech, Blacksburg VA Fall 2019, 2020 |
| Urban Teachers Resident Teacher College and Career Readiness Math | New Era Academy, Baltimore MD Fall 2018 |
Conference & Oral Presentations
| The Loewner Framework Beyond Linear Outputs 27th Conference of the International Linear Algebra Society, YMMOR 2026 | Blacksburg, VA May 26 – 29, 2026 |
| The Loewner Framework Beyond Linear Outputs Young Mathematicians in Model Order Reduction (YMMOR) Conference 2026 | Blacksburg, VA May 18 – 22, 2026 |
| Optimal-$\mathcal{H}_{2}$ approximation of linear quadratic output systems by multivariate rational interpolation Joint Mathematics Meeting 2026 | Washington, D.C. Jan 4 – 7, 2026 |
| $\mathcal{H}_{2}$-optimal model reduction by multivariate rational interpolation Challenges, Opportunities, and New Horizons in Rational Approximation | Banff, Canada Apr 6 – 11, 2025 |
| Interpolatory model reduction of dynamical systems with root mean squared error MATHMOD 2025, 11th Vienna International Conference on Mathematical Modeling | Vienna, Austria Feb 19 – 21, 2025 |
| Interpolatory $\mathcal{H}_{2}$ optimal model reduction of linear systems with quadratic outputs Model Reduction and Surrogate Modeling (MORe24) | La Jolla, CA Sep 9 – 13, 2024 |
| Generalizations of data-driven balancing: what to sample for different Riccati equation-based variants SIAM Conference on Applied Linear Algebra | Paris, France May 13 – 17, 2024 |
| $\mathcal{H}_{2}$-optimal model reduction of linear systems with quadratic outputs Young Mathematicians in Model Order Reduction (YMMOR) Conference 2024 | Stuttgart, Germany March 4 – 8, 2024 |
| Generalizations of data-driven balancing: What do you need to sample for different balancing-based reduced models? Mid-Atlantic Numerical Analysis Day | Philadelphia, PA November 10, 2023 |
| Interpolatory Matrix Approximations for Pilot Bus Selection and Disturbance Detection 2023 Algorithms for Threat Detection PI Workshop | Fairfax, VA October 10 – 12, 2023 |
| Interpolation-based $\mathcal{H}_{2}$-optimal model reduction of systems with quadratic outputs Nonlinear Model Reduction for Control | Blacksburg, VA May 22 – 26, 2023 |
| Structure-preserving Extensions of the QuadBT Framework SIAM Southeastern Atlantic Section Annual Meeting | Blacksburg, VA March 25 – 26, 2023 |
| Power System Event Localization via DEIM SIAM Conference on Computational Science and Engineering | Amsterdam, The Netherlands February 26 – March 3, 2023 |
Poster Presentations
| Interpolatory Approximations for PMU Data: Dimension Reduction, Pilot Bus Selection, and Event Detection 2024 AMPS/ATD PI Workshop | Alexandria, VA October 7 – 9, 2024 |
| On Balanced Truncation Error Bound and Sign Parameters Model Reduction and Surrogate Modeling (MORe22) 2022 | Berlin, Germany September 19 – 23, 2022 |
| On the Tightness of the Balanced Truncation Error Bound, with an Application to Arrowhead Systems Southeast Control Conference | Blacksburg, VA November 29 – 30, 2021 |
| A Tight Balanced Truncation Error Bound for a Certain Class of SISO Systems SIAM Conference on Computational Science and Engineering | Virtual March 1 – 5, 2021 |
| Minisymposium Organizer “Numerical Linear Algebra Tools for Model Order Reduction”, 27th Conference of the International Linear Algebra Society, ILAS 2026 Co-organizer: Mattia Mannuci (Karlsruhe Institute of Technology) | Blacksburg, VA May 2026 |
| Local Organizing Committee Member Young Mathematicians in Model Order Reduction (YMMOR) 2026 | Blacksburg, VA May 2026 |
| Minisymposium Organizer “Recent Advances in Model Order Reduction and Data-driven Modeling”, MATHMOD 2025, 11th Vienna International Conference on Mathematical Modeling Co-organizers: Hendrik Kleikamp (University of Münster), Steffen W. R. Werner (Virginia Tech), Jens Saak (MPI Magdeburg) | Vienna, Austria February 2025 |
| Organizing Committee Member Young Mathematicians in Model Order Reduction (YMMOR) |