Whence do research collaborations (in TCS) arise?

About ten days ago, I gave a talk to my colleagues at the Department of Computer Science at Reykjavik University, introducing my personal (and admittedly very biased) view of the past, present and future of ICE-TCS. 

After my presenta­tion, a colleague asked me how she could engage mathematicians and theoretical computer scientists in joint research. I gave her an answer off the top of my head, but it was clear that she was unconvinc­ed and felt that I was avoid­ing answering her question. (For the record, I basically told her that she should knock on our door, discuss with us the problems she was interested in solving and hope that they are of interest to us. I feel that many research collaborations arise from serendipity and that there is no recipe that is guaranteed to work.) 

The thought that she felt that I might have dodged her question prompted me to look back at my own research collabo­rations and how they came about. The rest of this post is the result of that quick-and-dirty reflection. Let me state right away that my list isn't meant to be exhausti­ve and that I won't mention many of the collaborations in which I have been lucky to be involved and that I have played a crucial role in shaping my academic development. 

Reading papers. One of my long-term research collaborations arose from reading a paper written by a colleague. His paper prompted my companion and me to ask ourselves whether we could prove a similar result to the one our colleague had shown in a different setting. We succeeded and sent him our paper. Subsequently, we invited him to visit us in Aalborg. That visit marked the start of a collaboration and friendship that has lasted for over 20 years.

Approaching a colleague via email for help in solving a problem. At some point, my companion and I were thinking about a research problem that had frustrated us for a while. I remembered reading a number of papers by a colleague on related topics, so I wrote to him, describing the problem, our attempts at solving it and where we had hit a brick wall. I asked him whether he would be interested in working with us on solving it. He did and that was one of the lucky breaks I have had in my research career. Once more, that collaboration offer via email led to mutual visits, other joint papers and, IMHO even more importantly, a long-term friendship that extended beyond work.
 

Available funding and building on one's mistakes. One day in 2009, an email in my mailbox alerted me to the availability of substantial funding for research collabo­ration between universities in country X and those locat­ed in Norway, Iceland and Lichtenstein. This opportunity was enticing, as I had never visited country X, so I asked myself: "Is there anyone there we might conceivably work with?'' Mulling over that question, I recalled that a colleague from country X had spotted an imprecision in a paper I had coauthored. 

I wrote to him, we applied for that funding jointly and got it. That successful grant application provided the funds for many research visits involving several people in our research groups. Those visits resulted in joint papers, another successful grant application and a number of friendships.

Coffee breaks at conferences. I have at least two exhibits under this heading. The first belongs to a previous geologic­al era (1991). I was attend­ing a conference at CMU and asked a colleague what he was working on. He told me
about a problem he was tackling, which I knew was also on the radar of a fellow researcher and on which I had started working independently. Eventually, after some email exchanges, that chat over coffee turned into a three-way collaboration that, thanks to my coauthors, produced one of my best papers.

Fast forward to 2017 and I'm in Rome to deliver an invited talk at a small conference. During the coffee break follow­ing my presentation, I was approached by a young research­er, with whom I had a number of pleasant conversations during the conference. Some time later, she sent me a draft paper dealing with a topic related to the content of my invited talk. I invited her to visit our research group in Reykjavik and to join the team working on a research project for which we had funding at the time. Those coffee-break conversations led to a collaboration and friendship that I hope will last for a long time. Meeting that colleague has been another of my lucky breaks.
 

Reading groups. Last, but by no means least, let me mention that my first research collaboration that did not involve my thesis supervisors arose when I read Gordon Plotkin's famous "Pisa Notes (On Domain Theory)" with a fellow PhD student. Reading that work led to our first joint paper in 1991 and a companionship that has lasted to this day. I heard Orna Kupferman give the following, tongue-in-cheek advice to young researchers: "Write papers with your twin-sister!" Mine might be: "Write papers with your companion in life!" 

Let me conclude by saying that serendipity and an actual friendship that extends beyond the confines of scientific work were the key aspects in my most pleasant and enduring collaborations. I apologise to the colleagues from whom I have learnt much over the years (former students and postdocs, as well as others) who were the prime movers in research collaborations I did not mention in this post. 

 I guess that this note provides much more information than my colleague was intending to receive, but I thought I should put it out for the benefit of the young researchers at Reykjavik University and at the Gran Sasso Science Institute, and of any reader I might have. 

How did your research collaborations arise? If you have anything to add to what I wrote above, and I am sure you do, add your contributions as comments to this post.