Interacting Particle Systems, Statistical Mechanics and Related Topics, A Conference to Honor the Contributions of Thomas M. Liggett on the Occasion of his 75th Birthday (conference website) took place at the Institute for Pure and Applied Mathematics (IPAM) on the campus of the University of California, Los Angeles (UCLA), from March 7–9, 2019. Amber Puha, one of the meeting’s organizers, writes:

Throughout his career, Tom Liggett has played an integral role in the development and proliferation of work in this area. It began in the early 1970s, when Chuck Stone, his then UCLA colleague, showed him a copy of Frank Spitzer’s 1970 article, “Interaction of Markov Processes,” (Advances in Mathematics 5, 246–290), saying, “I think you’ll find something interesting in this.” He did: it sparked a line of work that continued through his eventual induction into the National Academy of Sciences in 2008.

The list of speakers at the conference in Tom’s honor consisted of David Aldous, Maury Bramson, Pietro Caputo, Michael Damron, Pablo Ferrari, Alexander Holroyd, Matthew Junge, Kay Kirkpatrick, Oren Louidor, Hanbaek Lyu, Chuck Newman, Robin Pemantle, Eviatar Procaccia, Insuk Seo, Timo Seppäläinen, S.R.S. Varadhan, Maria Eulalia Vares and Ruth Williams. Almost 80 researchers registered for the event. It was a productive environment.

IPAM–UCLA proved to be an ideal location for the conference. Tom Liggett spent his entire academic career at UCLA, having arrived in 1969 and staying until his retirement in 2011. He was active in the department throughout his career, including serving as department chair from 1991–1994. He also met his wife, Christina, at UCLA: she worked in administrative support in the Department of Mathematics. The two fell in love and married in 1972. Outside of his academic career, Tom is a family man. He was thrilled that his wife Chris and their two children, Timothy and Amy, were able to attend social functions associated with this conference: they were all present at the dinner, with their own families in tow [although without Tom himself—see below]. His son Timothy gave an inspiring speech about growing up in the Liggett household. He also explained the challenges of convincing his children of their grandfather’s greatness, until he realized he could simply point out that grandpa was on Wikipedia.

I was his student in the mid-to-late 1990s. Being a Liggett student is a rarity. In his lengthy 42 years at UCLA, Tom only had nine students total: Norman Matloff, 1974 (UC Davis); Diane Schwartz, 1974 (CSU Northridge); Enrique Andjel, 1981 (U. Provence, Marseille, France); Dayue Chen, 1989 (Peking University); Xijian Liu, 1991 (US Census Bureau); Shirin Handjani, 1993 (San Diego); Amber Puha, 1998 (CSU San Marcos); Paul Jung, 2003 (KAIST); Alexander Vandenberg-Rodes, 2011. I consider myself fortunate to be among them. I am told that Tom found it tricky to mentor students. I didn’t notice that. He was a perfect advisor for me. He gave me an ideal problem that he didn’t know how to solve, but he suspected that some available tools might be applied to give headway. He held me accountable, and supported me when I needed a push, but without stealing my chance to develop as a researcher. I am forever grateful for his investment—and I am certain that I am not alone. Over his career, he mentored numerous postdoctoral scholars in the same fashion. In the spirit of fostering the development of the next generation of mathematical researchers, the conference included a poster session where many early career researchers presented: Erik Bates (Stanford); Bounghun Bock (Georgia Tech); Wai-Kit Lam (U. Minnesota); Jiho Lee (KAIST); Marcus Michelen (U. Pennsylvania); Carlos Pachecho (CINVESTAV); Joseph Stover (Gonzaga); Nantawat Udomchatpitak (UCSD); Jianfei Xue (U. Arizona); Fan Yang (UCLA); Jiayan Ye (Texas A&M); Mei Yin (U. Denver).

Unfortunately, Tom was unable to attend this conference in his honor. He managed to get bronchitis, which morphed into pneumonia and landed him a ten-day, all-inclusive stay at Santa Monica Hospital. Many from the conference made a trip to visit him there.

Tom’s son-in-law Darren filmed the after-dinner remarks, which featured Higgledy Piggledy tributes. Here is Holroyd’s offering:

Carefully, logic’ly,
Hypermethodic’ly
Scribb’ling away in Los
Angeles sun,

[He] opened the eyes of a
Whole generation: un-
countable state Markov
Chains can be fun!

Upon Tom’s return home, he got a private viewing of the entire affair. At home for just over two months, now, his recovery is slow, but steady. We encourage everyone to keep Tom in their warmest thoughts as he continues to recover.

Photos from the conference, by Matt Junge:

Conference photo outside of IPAM:

Between talks:

Marek Biskup making a post-banquet speech:

Amber Puha providing a proxy speech from Rick Durrett:

Tom’s family at the banquet:

Tom’s academic children and grandchild: