Congratulations to Sean Monahan, Sepehr Hajebi, and Alexandra Buhler, all of whom have won Faculty of Mathematics Graduate Research Excellence Awards.
Sean Monahan
Monahan graduated in 2024 with his PhD in Pure Mathematics, and is now working on a postdoc at the Technical University of Munich in Germany. He won a Graduate Research Excellence Award ($5000) for his paper “Horospherical Stacks and Stacky Coloured Fans.”
“I was absolutely thrilled when I got the news about receiving this award,” Monahan says. “It’s very encouraging to me to see that my research has this level of recognition early on in my career. I am extremely grateful to my PhD supervisor Matt Satriano for all of his guidance and support throughout my time at Waterloo…from start to finish, I really would not have received this award without him.”
Monahan explains that his paper works to develop a simplify working with complicated, abstract objects called “horospherical stacks.” He compares the process to consulting a German-English dictionary to help him speak and understand German. “The idea of my paper is to create a ‘complicated to simple’ dictionary between these ‘horospherical stacks’ and some new, fairly simple objects I called ‘stacky coloured fans.’ This dictionary makes it much easier to do explicit calculations and build intuition on the complicated objects.”
Alexandra Buhler
Alexandra Buhler graduated in 2024 with a PhD in Biostatistics. She co-won a Graduate Research Excellence Award ($2500) for her paper “Multistate models as a framework for estimand specification in clinical trials of complex processes.”
“It has been a wonderful surprise to receive recognition for the work I’m so passionate about!” Buhler says. “It makes me feel happy, proud and – most importantly – grateful, as this achievement would not have been possible without the guidance of my PhD supervisors Richard J. Cook and Jerry F. Lawless. They showed me continuous support throughout my entire journey and kept pushing me to grow as an independent researcher. I would also like to thank the SAS department for providing a great research environment. I am eager to continue my research and to build upon the expertise that I have acquired at Waterloo.”
The paper is the first in a series of four papers resulting from Buhler’s PhD research into statistical challenges in late-phase clinical drug development. The awarded paper “contributes to the important question of how randomized phase III trials of complex disease processes should be designed and analyzed to make causal, informed statements about the effects of an experimental treatment.”
Hajebi with his advisor Sophie Spirkl
Sepehr Hajebi
Sepehr Hajebi graduated in 2024 with his PhD in Combinatorics and Optimization. He is currently doing postdoctoral research at Waterloo, and will soon begin an appointment as junior faculty in the Department of Mathematics at Princeton University in the United States. He co-won a Graduate Research Excellence Award ($2500) for his paper “Induced subgraphs and tree decompositions XIII. Basic Obstructions in ℋ-free graphs for finite ℋ.”
“I am truly honored to receive this award,” Hajebi says. “This paper is part of a larger ongoing project that we’ve been working on for nearly four years now. It’s already been a long way, but there is still much to be done, and having my work recognized is surely motivating to continue pushing forward.” He is particularly grateful to his PhD supervisor Sophie Spirkl as well as his other coauthors on the paper: Bogdan Alecu and Maria Chudnovsky. “All my work on this project is in collaboration with Maria and Sophie, and many of the papers are also joint with varying sets of other collaborators. I am grateful for the countless insightful discussions I’ve had with all of them.”
Hajebi’s paper is the 13th in a series of 18 papers (and counting) exploring the induced subgraph version(s) of the grid theorem. “In this paper, specifically, we ask: ‘Suppose we choose only a finite number of graphs. Then what should those graphs be so that together they ‘represent’ the local structure of all non-basic induced subgraph obstructions to bounded treewidth?’” he explains. “Our main result answers this question completely.”