RODICA SIMION (1955-2000): An (almost) Perfect Enumerator and Human Being

By Doron Zeilberger

Department of Mathematics, Temple University, Philadelphia, PA 19122, USA.

Tuesday, Jan 11, 2000: I just found out the terrible news that Rodica Simion died last Friday. Like many of my fellow enumerators, I was looking forward to seeing her next week at the Special Session in Memory of Gian-Carlo Rota, that she organized (with Richard Stanley). The obvious and trite, yet undecidable, question is: Why Rodica?. She was not only one of the world's greatest leaders in Enumerative and Algebraic Combinatorics, and a very talented poet (read Rodica Simion's poem ) and painter, but one of the nicest, kindest, warmest, and most compassionate persons that I have ever known.

Writing about Rodica faces the same difficulty that she wrote about in her lovely poem. Any words are doomed to be very coarse polygonal approximations to such a C-infinity person like Rodica. But I'll do my best. First I have a confession to make. Writing these lines do not constitute any sacrifice of "research time". There is no way that I can concentrate on doing my regular "research" with such sad news on my mind, so I might just as well jot down my stream-of-consciousness recollections of Rodica.

First, let me explain the title. Why only almost perfect? During the break in one of the many conferences that Rodica organized (I think it was Richmond 1994), I saw her smoking a cigarette, outside, of course, and I teased her and told her: "Well, Rodica, I am relieved, I thought that you were perfect, but now I know that you have a vice". I am sure that this was her only imperfection.

Rodica was one of the few people in the world who are equally comfortable with "classical" (Wilf- and Foata- style) and "modern" (Rota- and Stanley- style) combinatorics. She combined her deep knowledge so well by finding beautiful and insightful connections between the two approaches that enriched each other. To get a very incomplete idea of her accomplishment, see my letter of recommendation on Rodica's behalf . To get a much better, and deeper, idea, you should read her publications.

Of her earlier work, I especially admired her seminal contributions (with Frank Schmidt) to the enumeration of what later got to be known as Wilf classes. In particular the gorgeous bijection between 123-avoiding and 132-avoiding permutations is one of my all-time-favorites. Of her later work, I found her studies of the poset of non-crossing partitions very insightful. Her invited talk at the SIAM meeting on Discrete Algorithms (1996), was one of the most stimulating talks that I have ever attended, as was her great talk at the May, 1993 "Jerusalem Combinatorics" conference, organized by Gil Kalai. In that talk she included quite a few Hebrew phrases, which made it obvious that Hebrew is yet another of the numerous languages that she knows well. Her talk aroused lots of interest, and lead to several questions, but she apologized that she was "too hyper" to answer them on the spot, and requested to be asked again later.

Rodica has at least one concept co-named after her: simsun permutations, discovered by her and Sheila Sundaram. Richard Stanley first called them SS-permutations, but Rodica objected to this unpleasant connotation, and suggested instead "simsun", and the name stuck. I am sure that the concept will find future applications.

Thanks to Rodica I got rid of at least one of my many prejudices. I always assumed that people who "organize conferences" are bossy and egocentric, people who enjoy "running the show". At least in Rodica's case, her motivation was purely altruistic: the exchange of knowledge and ideas. She always did a great job, and her conferences were always run so smoothly, and with great tact.

Luckily, with E-mail, I can have a rigorous proof of my theorem that Rodica was a wonderful Mensch.

I am sure that many others have numerous more proofs!

RODICA SIMION (or as she preferred to write her name: rodica simion) may be dead, but her memory will live for ever!

Added Jan. 16, 2000: Read Rodica Simion's short description of her research from her department's website, Math reviews of Rodica Simion's articles, and Abstracts from some of her NSF grants.,
Personal journal of Ekhad and Zeilberger

Home page of Doron Zeilberger