Media Release –
May 7, 2021
Canadian Mathematical Society |

# Dr. Christopher Liaw Named 2021 CMS Blair Spearman Doctoral Prize Recipient

OTTAWA, ON – The Canadian Mathematical Society is pleased to announce that Dr. Christopher Liaw (University of Toronto) is named the 2021 CMS Blair Spearman Doctoral Prize recipient. Dr. Liaw will receive his award at the CMS Winter meeting in Vancouver, BC.

Christopher Liaw is an outstanding researcher whose work has contributed fundamentally to mathematical foundations of machine learning. His dissertation addresses two important problems in theoretical machine learning.

The first problem is on identifying the sample complexity of learning mixtures of Gaussians — a long-standing open problem, with previous solutions requiring extra assumptions. Working together with several collaborators (Hassan Ashtiani, Shai Ben-David, Nick Harvey, Abbas Mehrabian, and Yaniv Plan), Dr. Liaw gave a precise characterization with minimal assumptions. Moreover, this work developed a new tool for distribution learning, which has since been applied to give the sample complexity for learning other classes of distributions. This resulted in a “best paper award” at NeurIPS 2018, an extraordinary distinction.

On another line focusing on online learning, Christopher Liaw considers online predictions with expert advice, which is a classic model in learning theory. The problem is to find an optimal algorithm to choose a probability distribution over experts where at each day each expert receives a reward and the algorithm receives the expected reward under the chosen distribution. The goal is that, at all times, the total reward earned by the algorithm so far must nearly equal the maximum total reward of any expert by that time. It has been known for decades that there is an algorithm whose reward is only 𝑂(√𝑡 ln 𝑛) smaller than the best expert’s reward and this is optimal up to constants. The open question of finding the optimal constant has been posed as early as 1997. Liaw’s work (joint with Nick Harvey, Ed Perkins, and Sikander Randhawa) resolved this question exactly for n = 2.

Liaw completed his PhD at the University of British Columbia in 2020 under the supervision of Nicholas Harvey. He has received several awards including a NeurIPS Best Paper Award as well as CGS-M, PGS-D and PDF fellowships from NSERC. He has an excellent publication record with three journal papers and ten papers in computer science conferences. He is currently a postdoctoral fellow at the University of Toronto.

**About the CMS Blair Spearman Doctoral Prize**

The CMS Blair Spearman Doctoral Prize recognizes outstanding performance by a doctoral student. The prize is awarded to one or two recipients of a Ph.D. from a Canadian university whose overall performance in graduate school is judged to be the most outstanding. Although the dissertation will be the most important criterion (the impact of the results, the creativity of the work, the quality of exposition, etc.) it will not be the only one. Other publications, activities in support of students and other accomplishments will also be considered.

**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:

Prof. Javad Mashreghi President Canadian Mathematical Society president@cms.math.ca |
or |
Prof. Kai Behrend (UBC) Chair, Doctoral Prize Selection Committee Canadian Mathematical Society Tel: (604) 822-1719 behrend@math.ubc.ca |