A year ago, I happened to be at the right place at the right time. I was a student in Boston, finishing up my Phd, and lived close to Harvard Square. Though I wasn't a student at Harvard, I'd gone regularly to their seminars for almost 5 years. Last year, I was lucky enough to attend a once-in-a-lifetime semester EV organized by BM, who in my opinion is one of the most influential mathematicians of the last 50 years.
BM felt there was a connection between 2 seemingly different areas of mathematics and called every expert in the two areas. They flew in from Europe, Asia and North America and it was quite mindblowing to see them all for a whole semester, giving lectures and working intensely in follow-up seminars. Some gave courses, some gave a lecture series and some just a short talk. It was like a 4 month conference and the intensity didn't slip throughout.
There was a small group in that very distinguished gathering which had a very significant presence. The whole semester had been split up into two to explore the connections. One of the two areas, (p-adic Langlands if you're curious) has been influenced heavily by a bunch of number theorists from Paris. They all came in April (apart from a few who came earlier) and there was intense curiousity about what they did.
What I found very amusing about them was how they all stuck together. In every lecture, they sat together at the back, talking and whispering in spite of other eminent mathematicians giving lectures. A few times I ended up sitting close to them, and couldn't understand their behaviour. It had nothing to do with lack of respect for the speaker, insecurity about their English (they're all fluent) or arrogance.
I've now spent almost 3 months in one of the many maths departments in Paris and observed them pretty closely. I've attended a few seminars outside the campus I'm in and in almost everyone I've gone to I've found the behaviour similar. I gave a talk in one of the seminars 2 weeks ago and didn't find the constant whispers annoying. It's something I've gotten used to now. There's a word for it in India (or at least in the north).
Adda (to me) means a bunch of friends who've known each other for a long time and feel comfortable only in each other's presence. They could be anywhere but the moment they see each other, they congregate together and tend to ignore the whole world. They tend to have a common meeting place (which is generally called the Adda or hangout) which is the centre of the world for them.
In my time in the US, I rarely came across such a place or group of friends. It was common for grad students to hang out in someone's office or meet at a particular cafe or bar, but it was fairly temporary. A few years at most, and then everyone moved on and once in a while one sees a few of them. But it's never the same as the original hangout which for an outsider can be a very boring place.
I guess I had an adda when I was an undergraduate in Delhi, but that was in a different decade and everyone's moved on to different places. My office in Brandeis had the feel of an adda, especially as I had a small fridge, a couch and a coffee-machine. But again, that was for a few years and when I went back for a few days in September, the whole character of that small office had changed.
My twin, on the other hand, has the quintessential adda. His entire clique moved from their undergrad institute in Ahmedabad to Delhi, and they all congregate in his studio almost everyday. I've known them for almost as long as he has, and each I'm back in Delhi I feel more comfortable with them than the few remaining friends I have from high school or college in Delhi. I know their background, the kind of work they do and also all the gossip. It's a comfortable place and group of people and though I'm the only non-designer in the group I don't feel like an outsider.
Paris is a place where an adda mentality seems quite common. I'd remarked to my host JT in the University about this, and he agreed. He has his own clique in the maths dept, though they're much younger and it's more work related. He said it's a common Parisian thing especially as almost all of them studied in Paris and have spent most of their academic life based in Paris.
I realised yesterday how the maths dept I'm in has its own adda. Almost all the young CNRS number theorists in the recent past have chosen this particular dept to be attached to (that's why I wrongly thought getting CNRS wasn't hard). JT teaches a course every Wednesday for 4 hours with a break in between for lunch. It's meant for his Phd students but I go for it along with a couple of other younger postdocs. It's an intense day as the class continues informally through lunch and the coffee/tea we get right after the marathon 4 hr class is over. But strangely, I don't feel too exhausted at the end of it as I feel familiar with most of the people in that group. The number theory seminar is on Fridays and each week a few of JT's former students show up from the other campuses for the talk, stay on for lunch and then continue talking well after lunch in the corridor or common room. Since they all have permanent positions in Paris and feel no need to move, it's unlikely to change. I can picture these guys in about 10-15 years time, still meeting every week and talking.
Addas exist everywhere I'm sure but in India and the US, most people I knew hardly ever stayed on in the same city throughout. Work, education and other factors contribute to people moving a lot. Since Paris is pretty much the centre of everything in France, there's no real need to move out as is the insecurity of the French of not speaking French. And with the amazing public transport and reasonable cost of living, people don't commute or drive too far everyday. Sitting in a cafe and hanging out with friends, taking the same train to work or the University or living fairly close to each makes it easier.
A month before I came to Paris, I didn't know a single person I could hope to stay with while looking for a flat. I thought of staying in a hostel while looking for a place and thought that since I was going to be here for just 3 months, I'd probably only hang out with people from the maths dept. It turned out to be completely different.
I'd met B in Toronto 3 years ago at a summer school and he was a student in Strasbourg at that point. I sent him a random email in September thinking I'd go there at some point for a few days to meet him. Turned out he's now a school-teacher in Paris and offered to let me stay with him and his girlfriend while I looked for a place. Since they moved from Strasbourg less than a year ago some of their friends have come as well and live not too far away. For the ones in Strasbourg, B&M's flat is the adda for all of them when they're in Paris. The first few days that I was staying with them there were about 6 of us sleeping at their flat one weekend but it felt fine. Very quickly, I became part of that clique and I've felt incredibly comfortable with all of them. Language is a bit of a barrier but when both sides are willing to make an effort, it's not too bad. Every time we all got out for dinner or someone cooks at their flat, it stretches on for at least 2-3 hours and nobody seems to be in a rush to leave.
I guess I've been lucky to become an outside member of a couple of small cliques so soon, but that's probably the biggest reason I've felt so comfortable here.