Homepage of Philip A. Ernst

Philip A. Ernst, Ph.D.


Chair in Statistics and
Royal Society Wolfson Fellow
Department of Mathematics
Imperial College London
p.ernst at imperial.ac.uk

2025 IMS Fellow


I am currently Chair (and Full Professor) in Statistics and Royal Society Wolfson Fellow at Imperial College London's Department of Mathematics. I was previously an Assistant Professor (2014–2018), Associate Professor (2019–2022), and Full Professor (2022–2023), all at Rice University's Department of Statistics.

My research has been recognized by an Institute of Mathematical Statistics (IMS) Medallion Award & Lecture, the title of IMS Fellow, an IMS Tweedie New Researcher Award, the inaugural INFORMS Donald P. Gaver, Jr. Early Career Award for Excellence in Operations Research, a Royal Society Wolfson Fellowship, a British Academy/Wolfson Fellowship, a COPSS Leadership Academy award, a Lebesgue Chair, and a U.S. Army Research Office (ARO) Young Investigator Award .

I gratefully acknowledge funding from the U.S. Army Research Office (ARO), the U.S. Office of Naval Research (ONR), the National Science Foundation (NSF), The British Academy and The Royal Society.

My research interests include:

Theory and Methodology: Applied probability, computational finance, exact distribution theory, mathematical finance, mathematical statistics, operations research, optimal stopping, queueing systems, statistical inference for stochastic processes, stochastic control, and time series analysis.

To get a taste of some of my research interests, see:

1) Brownian spider process (2025)
2) Yule's "nonsense correlation" solved! (2021)
3) The value of foresight (2018)

Applications: Actuarial science, agricultural economics, climate science, data science, quantitative economics, and portfolio management. Many of these applications are strongly related to my present work in the Lake Chad Basin. See this Abstract and Summary of Research Proposal describing my current efforts.

I am also strongly invested in teaching and mentoring. See:

a) George R. Brown Teaching Address at Rice University (2023)
b) An article about some of my efforts (2022)

I currently serve as Deputy Editor for Stochastics (2025–present). I am also an Associate Editor for the following five journals: Journal of the American Statistical Association: Theory & Methods (2023–present), Journal of Stochastic Analysis (2018–present), Mathematics of Operations Research (2021–present), Statistics & Probability Letters (2018–present), and The American Statistician (2024–present). Beginning January 2026, I will also be an Associate Editor for Journal of Theoretical Probability. I was previously Guest Editor-in-Chief for "In Memoriam: Larry Shepp," a special issue of Stochastic Processes and their Applications, which appeared in August 2022.

In August 2024, I began a three year term as an elected member of the Institute of Mathematical Statistics (IMS) Council.

Employment at Imperial College London, Department of Mathematics

(2022–present): Chair in Statistics and Royal Society Wolfson Fellow

Employment at Rice University, Department of Statistics

(2022–2023): Full Professor of Statistics (with tenure)
(2019–2022): Associate Professor of Statistics (with tenure)
(2018–2018): Assistant Professor of Statistics and Dobelman Family Junior Chair of Statistics
(2014–2018): Assistant Professor of Statistics

Education

Ph.D. in Statistics, The Wharton School of the University of Pennsylvania (2014)
M.A. in Statistics, The Wharton School of the University of Pennsylvania (2010)
B.A. cum laude in Statistics, Harvard University (2007)

Research In The News

A 90 Year Old Problem Solved

News


National and International Research Honors

Grant Support as PI

University Research Honors

  • 2022: Appointed Chair in Statistics at Imperial College London
  • 2022: Awarded Noah G. Harding Professorship in Statistics at Rice University (declined)
  • 2022: Awarded promotion to Full Professor at Rice University Press Release
  • 2019: Awarded early tenure at Rice University (Two Years Early) Press Release
  • 2019 Rice University School of Engineering Teaching and Research Excellence Award Press Release
  • (July 2018–Dec 2018) Rice University Dobelman Family Junior Chair of Statistics Press Release

University Teaching Honors

  • 2023 Rice University George R. Brown Award for Superior Teaching Press Release Rice News
  • 2022 Rice University George R. Brown Award for Excellence in Teaching (Rice University's most prestigious teaching award) Rice University Anouncement
  • 2021 Rice University George R. Brown Award for Superior Teaching Press Release Rice News
  • 2017 Rice University Nicolas Salgo Outstanding Teaching Award Press Release Rice News
  • 2016 Rice University Sophia Meyer Farb Prize for Teaching (Phi Beta Kappa Teaching Award) Press Release
  • 2015 Rice University Graduate Student Association Faculty Teaching and Mentoring Award Link
  • 2014 University of Pennsylvania Department of Statistics Donald S. Murray Prize for Excellence in Teaching
  • 2009 University of Pennsylvania Prize for Excellence in Teaching by Graduate Students Link

Federal Conference Funding for A symposium on optimal stopping as PI

Local and Private Conference Funding for A symposium on optimal stopping as PI

Representative Publications

  • Ernst, P.A. and Peskir, G. (2022) Quickest real-time detection of a Brownian coordinate drift. The Annals of Applied Probability, 32(4): 2652-2670. PDF Link to Journal
  • Ernst, P.A. and Franceschi, S. (2021) Asymptotic behavior of the occupancy density for obliquely reflected Brownian motion in a half-plane and Martin boundary. The Annals of Applied Probability, 31(6): 2991-3016. PDF Link to Journal
  • Ernst, P.A., Rogers, L.C.G., and Zhou, Q. (2020) When is it best to follow the leader? Stochastic Processes and their Applications, 130(6): 3394-3407. PDF Link to Journal
  • Ernst, P.A., Shepp, L.A., and Wyner, A.J. (2017) Yule's "nonsense correlation" solved! The Annals of Statistics 45(4): 1789-1809. PDF Link to Journal Video Talk

Papers Under Review or Invited Revision

  1. Ernst, P.A., Viens, F.G., and Yan, S.* (2025) Tests of independence for pairs of paths of non-stationary Gaussian processes. PDF
  2. Smyth, W., Ernst, P.A. and Miao, Y. (2025) Markowitz-informed neural networks (MINNs): An interpretable deep learning approach to portfolio optimization. PDF
  3. Ernst, P.A. and Mostovyi, O. (2025) The value of partial information. PDF
  4. Douissi, S., Ernst, P.A. and Viens, F.G. (2025) Asymptotics of Yule's nonsense correlation for Ornstein-Uhlenbeck paths: The correlated case. PDF
  5. Gerber, S., Smyth, W., Markowitz, H.***, Miao, Y., Ernst, P.A., and Sargen. P. (2024). Squeezing financial noise: A novel approach to covariance matrix estimation. PDF
  6. Ernst, P.A. and Stolyar, A.L. (2024) Asymptotic optimality of dynamic first-fit packing on the half-axis. PDF
  7. Berend, D., Ernst, P.A., Kontorovich, A., and Kumar, R. (2024) Exact expressions for the maximal probability that all k-wise independent bits are 1. PDF
  8. Ernst, P.A. and Huang, D.** (2024) Exact and asymptotic distribution theory for the empirical correlation of two AR(1) processes. PDF

Published Papers and Papers in Press

  1. Ernst, P.A. and Peskir, G. (2026+) The Gapeev-Shiryaev Conjecture. To appear in The Annals of Applied Probability. PDF
  2. Ernst, P.A. (2026+) Shepp and Shiryaev: The Russian Option. To appear in Statistics of Random Processes and Optimal Control: A Festschrift for Professor A.N. Shiryaev.
  3. Ernst, P.A. (2025) Exercising control when confronted by a (Brownian) spider: Part II. Queueing Systems, 109(2): 1–20. Link to Journal Video Talk
  4. Ernst, P.A. and Mei, H.* (2025) The minimax Wiener sequential testing problem. SIAM Journal on Control and Optimization, 63(1): 206–226. PDF Link to Journal
  5. Ernst, P.A., Rogers, L.C.G., and Zhou, Q.* (2025) Yule's "nonsense correlation": moments and density. Bernoulli, 31(1): 412–431. PDF Link to Journal
  6. Ernst, P.A., Mei, H*, and Peskir, G. (2024) Quickest real-time detection of multiple Brownian drifts. SIAM Journal on Control and Optimization, 62(3): 1832–1856. PDF Link to Journal
  7. Bednarz, E., Ernst, P.A., and Osekowski, A. (2024) On the diameter of the stopped spider process. Mathematics of Operations Research, 49(1): 346–365. PDF Link to Journal
  8. Ernst, P.A., Ma, X., Nazari, M.H., Qian, H., Wang, L.Y., and Yin, G. (2024) Numerical solutions of optimal stopping problems for a class of hybrid stochastic systems. Nonlinear Analysis: Hybrid Systems, 53: 101507. Link to Journal
  9. Ernst, P.A., Huang, D.** and Viens, F.G. (2023) Yule’s “nonsense correlation” for Gaussian random walks. Stochastic Processes and their Applications, 162: 423–455. PDF Link to Journal
  10. Ernst, P.A. and Mei, H.* (2023) Exact optimal stopping for multidimensional linear switching diffusions. Mathematics of Operations Research, 48(3): 1589–1606. PDF Link to Journal
  11. Ernst, P.A. and Peskir, G. (2022) Quickest real-time detection of a Brownian coordinate drift. The Annals of Applied Probability, 32(4): 2652–2670. PDF Link to Journal
  12. Ernst, P.A., Imerman, M.B., Shepp, L.A., and Zhou, Q.* (2022). Fiscal stimulus as an optimal control problem. Stochastic Processes and their Applications, 150: 1091–1108. PDF Link to Journal
  13. Bruss, F.T., Ernst, P.A., and Huang, D.** (2022) The rencontre problem. Stochastic Processes and their Applications, 150: 938–971. PDF Link to Journal
  14. Ernst, P.A., Kagan, A.M., and Rogers, L.C.G. (2022) The least favorable noise. Electronic Communications in Probability, 27: 1–11. Link to Journal (with PDF)
  15. Gerber, S., Markowitz, H.M.***, Ernst, P.A., Miao, Y.**, Javid, B., and Sargen, P. (2022) The Gerber statistic: a robust co-movement measure for portfolio optimization. The Journal of Portfolio Management, 48(3): 87–102. PDF Link to Journal
  16. Ernst, P.A. and Franceschi, S. (2021) Asymptotic behavior of the occupancy density for obliquely reflected Brownian motion in a half-plane and Martin boundary. The Annals of Applied Probability, 31(6): 2991–3016. PDF Link to Journal
  17. Ernst, P.A., Franceschi, S., and Huang, D.** (2021) Escape and absorption probabilities for obliquely reflected Brownian motion in a quadrant. Stochastic Processes and their Applications, 142: 634–670. Link to Journal (with PDF)
  18. Ernst, P.A. and Rogers, L.C.G. (2020) The value of insight. Mathematics of Operations Research, 45(4): 1193–1209. PDF Link to Journal
  19. Ernst, P.A., Peskir, G., and Zhou, Q.* (2020) Optimal real-time detection of a drifting Brownian coordinate. The Annals of Applied Probability 30(3): 1032–1065. PDF Link to Journal
  20. Ernst, P.A., Rogers, L.C.G., and Zhou, Q.* (2020) When is it best to follow the leader? Stochastic Processes and their Applications, 130(6): 3394–3407. PDF Link to Journal
  21. Ernst, P.A. and Shaman, P. (2019) The bias mapping of the Yule-Walker estimator is a contraction. Statistica Sinica, 29(4):1831–1849. Link to Journal
  22. Ernst, P.A. and Viens, F.G. (2019) In memory of Larry Shepp: An editorial. High Frequency, 2(2): 74–75. Link to Journal
  23. Ernst, P.A., Kendall, W.S., Roberts, G.O, and Rosenthal, J.S. (2019) MEXIT: Maximal un-coupling times for stochastic processes. Stochastic Processes and their Applications, 129(2): 355–380. PDF Link to Journal
  24. Ernst, P.A. and Soleymani, F. (2019) A Legendre-based computational method for solving a class of Ito stochastic delay differential equations. Numerical Algorithms, 80(4): 1267–1282. PDF Link to Journal
  25. Ernst, P.A., Kimmel, M., Kurpas, M., and Zhou, Q.* (2018) Heavy-tailed distributions in branching process models of secondary cancerous tumors. Advances in Applied Probability, 50(A): 99–114. PDF Link to Journal
  26. Ernst, P.A., Asmussen, S., and Hasenbein, J.J. (2018) Stability and busy periods in a multiclass queue with state-dependent arrival rates. Queueing Systems, 90: 207–224. PDF Link to Journal
  27. Zhou, Q.*, Ernst, P.A., Morgan, K.L, Rubin, D.B., and Zhang, A. (2018) Sequential rerandomization. Biometrika, 105(3): 745–752. PDF Link to Journal
  28. Ernst, P.A., Rogers, L.C.G, and Zhou, Q.* (2017) The value of foresight. Stochastic Processes and their Applications, 127(12): 3913–3927. PDF Link to Journal
  29. Ernst, P.A., Shepp, L.A., and Wyner, A.J. (2017) Yule's "nonsense correlation" solved! The Annals of Statistics 45(4): 1789–1809. PDF Link to Journal Video Talk
  30. Ernst, P.A. (2017) Minimizing Fisher information with absolute moment constraints. Statistics and Probability Letters 129: 167–170. Link to Journal
  31. Ernst, P.A. and Grigorescu, I. (2017) Asymptotics for the time of ruin in the war of attrition. Advances in Applied Probability 49(2): 388–410. PDF Link to Journal
  32. Ernst, P.A., Thompson, J.R., and Miao, Y.** (2017). Portfolio selection: the power of equal weight. In Models and Reality: A Festschrift for James R. Thompson , pp. 225–236. PDF
  33. Ernst, P.A., Thompson, J.R., and Miao, Y.** (2017) Tukey's transformational ladder for portfolio management. Financial Markets and Portfolio Management 31(3): 317–355. PDF Link to Journal
  34. Ernst, P.A. and Shepp, L.A. (2017) On occupation times of the first and third quadrants for planar Brownian motion. Journal of Applied Probability 54(1): 337–342. PDF Link to Journal
  35. Ernst, P.A., Brown, L.D., Shepp, L.A., and Wolpert, R.L. (2017) Stationary Gaussian Markov processes as limits of stationary autoregressive time series. Journal of Multivariate Analysis 155: 180–186. Link to Journal
  36. Ernst, P.A. (2017) On the arbitrage price of European call options. Stochastic Models 33(1): 48–58. Link to Journal
  37. Ernst, P.A. and Shepp, L.A. (2016) Eliminating a loophole in the national flood insurance program. Law, Probability and Risk 15(4): 251–258. Link to Journal
  38. Ernst, P.A., Pemantle, R., Satopaa, V., and Ungar, L. (2016) Bayesian aggregation of two forecasts in the partial information framework. Statistics and Probability Letters 119: 170–180.
  39. Ernst, P.A. (2016) Exercising control when confronted by the (Brownian) spider. Operations Research Letters 44: 487–490. PDF Link to Journal
  40. Ernst, P.A. and Shepp, L.A. (2016) On the time for Brownian motion to visit every point on a circle. Journal of Statistical Planning and Inference 171: 130–134. PDF Link to Journal
  41. Ernst, P.A. and Shepp, L.A. (2015) Revisiting a theorem of L.A. Shepp on optimal stopping. Communications on Stochastic Analysis 9(3): 419–423. PDF Link to Journal
  42. Ernst, P.A., Foster, D.P., and Shepp, L.A. (2014). On optimal retirement. Journal of Applied Probability 51(2): 333–345. Link to Journal


Current Ph.D. students (sole advisor)

Current Postdoctoral Fellows (sole advisor)

Former Ph.D. Students (sole advisor)

  • Dongzhou Huang (graduated May 2022)
    • First Job: Assistant Professor of Statistics (tenure-track), Colorado State University.
  • Yizhou Xia (graduated December 2019)
    • First Job: Data Strategist at BP

Former Postdoctoral Fellows (sole advisor)

  • Hongwei Mei (May 2020–August 2022)
    First Job: Assistant Professor of Mathematics and Statistics (tenure-track), Texas Tech University.
  • Richard Chen (September 2020–August 2021)
    First Job: Research scientist, Amazon.
  • Quan Zhou (April 2017–August 2019)
    First Job: Assistant Professor of Statistics (tenure-track), Texas A&M University

Public Outreach

Course Reviews

At Rice University, I taught STAT 310 (undergraduate probability and statistics), STAT 581 (A Ph.D. course in measure-theoretic probability), and STAT 650 (A Ph.D. course in stochastic differential equations). Course reviews may be found below.

As a Ph.D. candidate at Wharton Statistics, I taught STAT 101 (undergraduate business statistics). The course review is below.

STAT 101 Instructor Review