Media Release –
April 3, 2023
Canadian Mathematical Society |

# 2023 CATHLEEN SYNGE MORAWETZ PRIZE AWARDED TO DR. STEFANOS ARETAKIS

OTTAWA, ON – The Canadian Mathematical Society (CMS) is pleased to announce that Dr. Stefanos Aretakis (University of Toronto) has been named the recipient of the 2023 Cathleen Synge Morawetz Prize. This prize was awarded for an outstanding research publication, or a series of closely related publications on the topic of Applied Mathematics for Dr. Aretakis’ groundbreaking work on instability in extremal black holes (what has come to be known as *Aretakis instability),* conservation laws for wave equations, and their long-term behaviour in asymptotically flat backgrounds. Highlights of this work include:

- Aretakis,
*Stability and Instability of Extreme Reissner-Nordstr**ö**m Black Hole Spacetimes for Linear Scalar Perturbations I.*Commun. Math. Phys. (2011) 307, 17–63. - Angelopoulos, S. Aretakis, and D. Gajic
*Horizon Hair of Extremal Black Holes and Measurements at Null Infinity*, Phys. Rev. Lett. 121, 131102 (2018). - Aretakis,
*The Characteristic Gluing Problem and Conservation Laws for the Wave Equation on Null Hypersurfaces*, Annals of PDE (2017), 3:3. - Angelopoulos, S. Aretakis & D. Gajic
*A Vector Field Approach to Almost-Sharp Decay for the Wave Equation on Spherically Symmetric, Stationary Spacetimes*, Annals of PDE 4: 15 (2018).

The first in this series of notable contributions is the influential, single-author publication in 2011 (and another in 2015) where Dr. Aretakis discovered a surprising instability mechanism in extremal black holes, which he established using conceptually and technically novel methods. This resolved a longstanding open question in General Relativity, and has had a major impact on research in the field. Coincidentally, Cathleen Synge Morawetz herself had studied an analogous mathematical question in R^{n}. Dr. Aretakis and his team subsequently used asymptotics of solutions of the wave equation to propose a new observational signature for extremal black holes, published as editor’s selection in Phys. Rev Lett (2018) and later in full mathematical detail in Adv. Math. This line of Dr. Aretakis’ work has continued to impact not only physics but also mathematics, identifying (2017) a novel set of conservation laws improving general understanding of wave equations in Lorentzian geometry, and, in a highly-cited Annals of PDE paper (2018), studying long-time behaviour of waves on very general classes of asymptotically flat backgrounds. A professor at the University of Toronto and Dr. Aretakis’ colleague Dr. Robert J. McCann, FRSC states;

“Stefanos Aretakis has made deep contributions to the mathematics of general relativity, Einstein’s theory of gravity. One of the holy grails in the area has been to conﬁrm the stability of the Kerr family of (non-extremal) rotating black holes. That this stability question might have a diﬀerent answer in the extremal case (which rotate as quickly as possible for their mass), seems to have been largely overlooked prior to his work. Aretakis showed they are unstable, but the instability manifests itself only in norms of suﬃcient smoothness: one sees the instability not at the level of zeroth or ﬁrst derivatives, but only at the level of second derivatives of the solution of a wave equation, representing a perturbation of the geometry of the black hole. Given its essentially mathematical nature, his work has proven unusually inﬂuential in the physics community, where the Aretakis instability is now widely discussed, and its consequences are helping to inspire the next generation of experiments in high-energy physics and gravitational wave observations.”

Dr. Stefanos Aretakis is an Associate Professor of Mathematics at the University of Toronto. He received his PhD in 2012 at the University of Cambridge, and held a Veblen Research Instructorship and Assistant Professorship at Princeton University prior to joining the University of Toronto. His main research interests are in Differential Geometry, Analysis of PDEs, and General Relativity.

Dr. Aretakis has contributed outstanding publications to his field, which have had a profound impact in his areas of research. The CMS is delighted to award him the well-deserved 2023 Cathleen Synge Morawetz Prize.

**About the Cathleen Synge Morawetz Prize**

The Cathleen Synge Morawetz Prize is for an author(s) of an outstanding research publication. A series of closely related publications can be considered if they are clearly connected and focused on the same topic. The recipient(s) shall be a member of or have close ties to the Canadian mathematical community.

For more information, visit the Cathleen Synge Morawetz Prize page.

**About the Canadian Mathematical Society (CMS)**

The CMS is the main national organization whose goal is to promote and advance the discovery, learning and application of mathematics. The Society’s activities cover the whole spectrum of mathematics including: scientific meetings, research publications, and the promotion of excellence in mathematics competitions that recognize outstanding student achievements.

**For more information, please contact**:

Dr. Susan Cooper (uManitoba) Chair, CMS Research Committee Canadian Mathematical Society chair-resc@cms.math.ca |
or | Dr. Termeh Kousha Executive Director Canadian Mathematical Society tkousha@cms.math.ca |