(Photo from facebook.com)

Michael Cohen, one the most brilliant young minds of our field, recently passed away in Berkeley.

After going to MIT for college, Michael worked for Facebook and was a graduate student at MIT. This semester, he was at Berkeley as Simons Fellow in connection with the program on optimization at the Simons Institute.

In a few short years, Michael left his mark on a number of problems that are close to the heart of in theory‘s readers.

He was part of the team that developed the fastest algorithm for solving systems of linear equations in which the matrix of constraints is a graph Laplacian (or, more generally, is symmetric and diagonally dominated), running in time $O(m \sqrt {\log n})$ where $m$ is the number of non-zero entries of the matrix and $n$ is the number of variables.

He also worked on matrix approximation via subsampling, on algorithms that approximate random walk properties, on algorithms for flow and shortest paths, and on geometric algorithms.

My favorite result is his single-author paper giving a polynomial time construction of bipartite Ramanujan graphs of all degree and all sizes, making the approach of Marcus, Spielman and Srivastava constructive.

Michael was a unique person, who gave a lot to our community and had touched several lives. His loss is an unspeakable tragedy that I still find very hard to process.

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## 8 thoughts on “”

1. This is truly a great loss for both the field and the theory community. Michael really was a unique, thoughtful person who had a non-standard approach to science (and the world at large). His mind was always going 100mph, so it was remarkable that he didn’t miss a beat in calibrating (i.e., slowing down) for an audience (for those who didn’t know him, here is a talk he gave in Banff last summer that exhibits this clarity: https://www.birs.ca/events/2016/5-day-workshops/16w5111/videos/watch/201608011534-Cohen.html).

Despite the impressive achievements that Luca describes, one got the sense that this was all a warmup for Michael. It’s really disheartening that we won’t get to see what comes next.

2. Anyone who has spent time on the 5th and 6th floors of the Stata center at MIT (where the theory group sits) knows Michael. It was impossible to ignore his energy, wonder, and excitement for research, current events, and everything in between. Michael always seemed surrounded by a group of friends happy to banter or simply to listen. He was a natural teacher — truly kind, humble, welcoming, positive, and always willing to slow his thoughts for a moment to share his brilliance.

We all learned so much from Michael and sadly had so much more to learn. I wish we had more time to simply absorb the pure positivity and curiosity of his world view. It was unmatched in anyone else I’ve known.

Its hard to accept that we won’t be hearing Michael wandering around Stata anymore. We lost a truly unique person. Michael was a light that will shine in my memory for the rest of my life and he will be profoundly missed.

3. Pingback: Tragic Losses | A bunch of data

4. Michael was brilliant in so many ways — from the clarity he brought to research to the immense energy and excitement he emanated every day. Like many who knew him I admired Michael greatly. He was unusually humble and giving because, if there was one thing he prioritized over understanding his world, it was helping others understand. We have lost an incredible and unique spirit. I’m deeply saddened for his family, his friends, and our community, but I also feel incredibly lucky for the time we had with Michael.

5. This is Michael’s mother. Thank you for this beautiful post. Is there any way I can get a copy of the picture? . Thanks so much.