Yunus Emre Demirci

Education

• 2026 Ph.D. in Mathematics Queen’s University, Kingston, ON, Canada

  Advisor: Prof. Serdar Yüksel. Thesis: Regularity of Non-Linear Filter Dynamics and Robustness and Approximations in Stochastic Control with Partial Information.

• 2021 M.Sc. in Mathematics Boğaziçi University, Istanbul, Turkey

  Advisor: Prof. Ümit Işlak. Thesis: Edge Flipping in Graphs.

• 2019 B.Sc. in Computer Engineering Boğaziçi University, Istanbul, Turkey

  Advisor: Prof. A. C. Cem Say. Thesis: Modeling and Simulating Cellular Automata.

Research Interests

My research interests lie broadly in stochastic control, nonlinear filtering, and partially observed Markov decision processes (POMDPs). I am particularly interested in the robustness, stability, and approximation of control and filtering systems under partial information.

In discrete-time settings, I have studied the impact of model mismatch and quantization on the stability and convergence of belief-state dynamics, deriving explicit bounds on value functions and identifying conditions for near-optimality. In particular, I have investigated the Wasserstein and total-variation continuity of filter kernels under model perturbations, robustness in the average-cost setting, and unique ergodicity results for control-free models.

More recently, I have been focusing on continuous-time stochastic systems under partial observation, especially diffusion processes — studying robustness to prior mismatch and how discrete-time approximations via time and observation quantization can be used to analyze and control such systems.

Publications

Preprints

1. Demirci, Y. E., Pradhan, S.., Yüksel, S. Near Optimal POMDP Approximation of Controlled Diffusions with Partial Information.
2. Demirci, Y. E., Kara, A. D., Yüksel, S. Sensitivity of Filter Kernels and Robustness to Incorrect Transition and Measurement Kernel Perturbations in Partially Observable Stochastic Control. arXiv:2508.10658v3.
3. Demirci, Y. E., Kara, A. D., Yüksel, S. Refined Bounds on Near Optimality Finite Window Policies in POMDPs and Their Reinforcement Learning. arXiv:2409.04351.

Publications

1. Demirci, Y. E., and Yüksel, S. (2025). Unique Ergodicity of Non-Linear Filters via Reachability and Uniform Weak Continuity. Electronic Communications in Probability, 30, 82, 1–15. https://doi.org/10.1214/25-ECP732
2. Demirci, Y. E., Kara, A. D., and Yüksel, S. (2024). Average Cost Optimality of Partially Observed MDPs: Contraction of Non-Linear Filters and Existence of Optimal Solutions and Approximations. SIAM Journal on Control and Optimization, 62(6), 2859–2883. https://doi.org/10.1137/24M1643736
3. Demirci, Y., Işlak, Ü., Özdemir, A. (2023). Mixing time bounds for edge flipping on regular graphs. Journal of Applied Probability, 1–16. https://doi.org/10.1017/jpr.2023.3
4. Çiçeksiz, A., Demirci, Y. E., Işlak, Ü. (2023). The Variance and the Asymptotic Distribution of the Length of Longest k-alternating Subsequences. Discrete Mathematics and Theoretical Computer Science, 25(1). https://doi.org/10.46298/dmtcs.10296
5. Demirci, Y. E., Ekim, T., Yıldız, M. A. (2023). Defective Ramsey Numbers and Defective Cocolorings in Some Subclasses of Perfect Graphs. Graphs and Combinatorics, 39(1), 18. https://doi.org/10.1007/s00373-023-02612-4
6. Demirci, Y. E., Işlak, Ü., Yıldız, M. A. (2023). On a cover time problem on a dynamic graph with steps at random times. Statistics and Probability Letters, 197, 109821. https://doi.org/10.1016/j.spl.2023.109821
7. Demirci, Y. E., Ekim, T., Gimbel, J., Yıldız, M. A. (2021). Exact values of defective Ramsey numbers in graph classes. Discrete Optimization, 42, 100673. https://doi.org/10.1016/j.disopt.2021.100673

Conference Proceedings

1. Demirci, Y. E., Kara, A. D., & Yüksel, S. (2025). Sensitivity of Filter Kernels and Robustness to Incorrect Transition and Measurement Kernel Perturbations in Partially Observable Stochastic Control. In Proceedings of the 2025 IEEE 64th Conference on Decision and Control (CDC 2025), Rio de Janeiro, Brazil, December 10-12, 2025.
2. Demirci, Y. E., Kara, A. D., & Yüksel, S. (2025). Wasserstein Regularity of Nonlinear Filters As Belief-MDPs, and Implications on Ergodicity, Optimality and Learning for POMDPs. In Proceedings of the 2025 American Control Conference (ACC 2025), Denver, Colorado, USA, July 8-10, 2025.
3. Demirci, Y. E., Kara, A. D., & Yüksel, S. (2024). Average Cost Optimality of Partially Observed MDPs: Contraction of Non-Linear Filters and Existence of Optimal Solutions and Approximations. In Proceedings of the 2024 American Control Conference (ACC 2024), Toronto, Canada, July 8-12, 2024.

Honors & Awards

• 2019 – 2021 Graduate Fellowship The Scientific and Technological Research Council of Turkey (TÜBİTAK)
• 2012, 2011 International Mathematical Olympiad — Silver Medal (IMO 2012 · IMO 2011)
• 2012, 2011, 2010 National Mathematical Olympiads of Turkey — Gold Medal (2010, 2012) — Silver Medal (2011)

Scholarships

• 2025 – 2026 Queen Elizabeth II Scholarship in Science and Technology Queen’s University · $15,000
• 2024 – 2025 Ontario Graduate Scholarship (OGS) Queen’s University · $15,000
• 2023 – 2024 Ontario Graduate Scholarship (OGS) Queen’s University · $15,000

Teaching Experience

• 2026 Teaching Fellow — Engineering Math Project Queen’s University
• 2025 Teaching Fellow — Introduction to Operations Research Queen’s University
• 2024 Teaching Fellow — Introduction to Linear Algebra Queen’s University
• 2023 Teaching Assistant Queen’s University

  Differential and Integral Calculus · Complex Analysis · Graph Theory · Control of Stochastic Systems

• 2022 Teaching Assistant Queen’s University

  Calculus I · Vector Calculus · Advanced Calculus · Linear Algebra · Introduction to Linear Algebra

• 2021 Teaching Assistant Queen’s University · Boğaziçi University

  Queen’s: Vector Calculus, Advanced Calculus.  Boğaziçi: Differential Equations, Introduction to Probability and Statistics.

More on the teaching page.

Talks

• Nov 2025 Stability, Approximation, and Robustness of Optimal Policies in POMDPs. ISS Informal Systems Seminar, McGill University, Montréal, QC, Canada.
• Sep 2025 Unique Ergodicity of Non-Linear Filters via Reachability and Uniform Weak Continuity. Weekly Seminar on Stochastic Control, Queen’s University, Kingston, ON, Canada.
• Jul 2025 Wasserstein Regularity of Nonlinear Filters As Belief-MDPs, and Implications on Ergodicity, Optimality and Learning for POMDPs. ACC 2025, Denver, Colorado, USA.
• May 2025 Stability, Ergodicity, and Optimal Control in Partially Observed Markov Processes: Wasserstein Contraction Approach. 10th Meeting on System and Control Theory, HEC Montréal, QC, Canada.
• May 2025 Wasserstein Perturbation Bounds on Filter Kernels in State Transition and Measurement Kernel Uncertainty. Weekly Seminar on Stochastic Control, Queen’s University, Kingston, ON, Canada.
• Mar 2025 Robustness to Incorrect Models in Partially Observable Markov Decision Processes via Wasserstein Regularity of Filter Dynamics. Weekly Seminar on Stochastic Control, Queen’s University, Kingston, ON, Canada.
• Oct 2024 Application of the Birkhoff–Hopf Contraction Theorem: Stability of Nonlinear Filters. Weekly Seminar on Stochastic Control, Queen’s University, Kingston, ON, Canada.
• Sep 2024 Refined bounds on near optimality of finite window policies in POMDPs. Weekly Seminar on Stochastic Control, Queen’s University, Kingston, ON, Canada.
• Jul 2024 Average Cost Optimality of Partially Observed MDPs: Contraction of Non-Linear Filters and Existence of Optimal Solutions and Approximations. ACC 2024, Toronto, ON, Canada.
• Feb 2024 Average Cost Optimality in Partially Observable Markov Decision Processes: Implications for Robustness and Optimal Policy Approximation. Weekly Seminar on Stochastic Control, Queen’s University, Kingston, ON, Canada.
• Dec 2023 On Regularity and Ergodicity of Partially Observable Markov Decision Processes. CMS Winter Meeting, Stochastic Control Theory and Applications, Montréal, QC, Canada.
• May 2023 Unique Ergodicity of Non-Linear Filters. 9th Meeting on System and Control Theory, University of Waterloo, ON, Canada.
• Mar 2023 On Unique Ergodicity of Non-Linear Filters. Weekly Seminar on Stochastic Control, Queen’s University, Kingston, ON, Canada.
• Nov 2022 Average Cost Dynamic Programming Equations for POMDP. Weekly Seminar on Stochastic Control, Queen’s University, Kingston, ON, Canada.
• Nov 2020 Edge Flipping in Graphs. Student Probability Seminar Series, Boğaziçi University, İstanbul, Türkiye.
• Jul 2020 Generating Random Graphs. Discrete Mathematics Days, Boğaziçi University, İstanbul, Türkiye.
• Mar 2020 Alternating Subsequences. Student Probability Seminar Series, Boğaziçi University, İstanbul, Türkiye.
• Nov 2019 Defective Ramsey Numbers in Graph Classes. Graph Theory Workshop IX, Istanbul Center for Mathematical Science, İstanbul, Türkiye.

Languages & Technical Skills

• Languages Turkish (native), English (fluent).