Here are some memories about Dick Gross, who sadly just passed away very recently.
Nothing was quite as reassuring as having Dick Gross in your audience. Inevitably, when your talk was done, he would both compliment you on it and have something very interesting mathematical to say. The last time this happened to me was at the Tate 100 conference in March. Dick was a student of Tate, and although he wasn’t able to come in person, he gave some prerecorded reminiscences. (Many of the very nice things Dick says about Tate can also be said about Dick.) But after my own talk (broadcast on Zoom), I still got an email from Dick titled “great talk,” which led to an interesting conversation between the relationship between Serre’s Conjecture and Artin’s Conjecture, as well as some analogs of these questions for \(\mathrm{GSp}_4\). I’m guessing I am not the only speaker at that conference to get such an email!
It’s hard to know where to start. Dick was a great mathematician — his collaboration with Don produced surely one of the greatest theorems in modern number theory (and many more great theorems besides; the paper on difference of singular moduli, for example). He was a great expositor — his Duke paper is a masterly exposition of quite a lot of the arithmetic theory of modular forms (and also a wonderful theorem). He was a great mathematician to chat with at afternoon tea or in the corridor, when you could learn all sorts of clever ideas that weren’t written down anywhere else. He was a pioneer in the arithmetic theory of automorphic forms on higher ranked groups. As Dick himself used to say, you start with \(\mathrm{GL}_2\), then remove the \(\mathrm{L}\), and then the \(2\).
In contrast, the first time I interacted with Dick, a little shy of 25 years ago, he was at the beginning of a second career beyond mathematics in administration, having become math department chair before his tenure as Dean. It was his job to let me know that the department was offering me a BP position. One line from that email was as follows:
For now, let me say how delighted I would be if you would join us next year, as a colleague.
This certainly made me feel pretty good at the time, and it is a line I have come back to and reused myself as a junior hiring chair. (Another line in that email, “I hear you are now an uncle. Behave accordingly”, is less versatile.) More generally, Dick was charming in the best possible way — combining not only the polish that this word suggests, but with an underlying spirit of someone who was attentive, personable, and conscientiously kind.
My interactions with Dick at Harvard mostly continued through his capacity as chair. At one point, I realized that I had been slightly overpaid (I was getting a mix of money both from Harvard and from AIM). His remark at the time, which I can only paraphrase due to the passage of time — said entirely deadpan — was something like, “I have two pieces of advice in life: avoid paying your taxes as much as possible, and don’t tell anyone if you are overpaid.”
There was only one moment where I saw him anywhere approaching being exasperated (though presumably that must have happened quite often as Dean). DeBacker and I had been put in charge of the colloquium committee. The speakers had already been invited by the time it started, so the main task was simply organizing the dinners for the speakers. This was all done by DeBacker, who paid for everything himself and was later reimbursed. On one occasion, Richard Borcherds gave the colloquium, and we ended up going to a quite fancy restaurant (Harvest) in Harvard Square. I don’t think a single senior faculty member came, but lots of graduate students did. We were, I think, quite liberal with the purchase of some nice bottles of Chablis. As you can imagine, the price of the dinner (fully paid by the department) was on the higher side, and at some point it must have gone to Dick’s desk to be approved. I believe Dick’s remark to Stephen was along the lines of, “I don’t want to hear the words ‘colloquium dinner,’ ‘graduate students,’ and ‘$2000’ in the same sentence ever again.”
My best mathematical interactions with Dick mostly came through casual conversations and emails (or even comments on this blog!). I did once answer an actual mathematical question raised by Dick in a joint Inventiones paper with Lubin from 1986. They asked whether a certain Hecke algebra of level \(\Gamma_0(p^2)\) localized at an Eisenstein ideal above \(p\) was always a discrete valuation ring, and I found this could be answered in the positive using ideas of Chenevier and Bellaiche.
Of course, that particular question and answer are no more than mathematical ephemera. But Dick’s legacy — as a mathematician and as a person — will live on.
More from other sources:
An article on Dick in Celebratio Mathematica
Faculty Spotlight Harvard Interview