I met Tom Liggett in the academic year 2015–2016, when I was an adjunct assistant professor at UCLA. But before that I was fortunate enough to have written a paper with him and my Ph.D. advisor,, on the contact process with fast voting. I can still remember how I was totally amazed by his mastery and magic in discrete harmonic analysis. Tom had officially retired before I went to UCLA, but still he was the first person who took me to the beautiful faculty club (and showed me how to register there)! We met roughly every one or two weeks when I was at UCLA, and I was deeply touched by his lifelong focus and devotion to discrete probability.
In addition to his reputation as a world-class mathematician, Tom was also known as a wonderful mathematical educator. Early in 2016, I brought him my undergraduate probability teaching evaluations for his feedback. Tom told me the magic formula he used to help people improve their teaching when he served as Director of Undergraduate Studies at the math department of UCLA. He advised me to take a closer look at the comments and find out what the complaints have in common. With this focus we quickly found that I needed a more careful design to my blackboard-writing, and that I needed to avoid constant erasing of recent material. I still find his recommendation to be the most practical guideline for improving my teaching.
After leaving UCLA, I frequently sent him updates about my research and career. Tom’s replies were always warm, encouraging, and full of wisdom. Towards the beginning of 2019, I still received remarks from him with great insight regarding the threshold-one contact process/voter models. At some point, I began (wrongly) to recall that our talks were just on mathematics. But when I started preparing this tribute, all the stories he shared with me about his life reemerged miraculously: those of his early life in the Midwest and Argentina, those of LA air pollution in the old days, and those of his evacuation in a wildfire by the National Park Rangers.
I am so deeply sorrowed by Tom’s passing away. It is an honor to have received his precious help and advice in research, teaching, and life.
Yuan Zhang is Assistant Professor at Peking University's School of Mathematical Sciences in Peking, China.