Fragment of Memory with Fred Cohen

Fred was my academic grandfather. 

My first paper during Phd career was handled by him at AGT in 2016.

In 2017-18 and 2020, we discussed my possible visit to Rochester several times, but unfortunately did not make it happen. He also helped me to apply his postdoc position, but I took the tenure-track position at AMSS in the end. 

I met him personally once at Fields Institute in Jan. 2020. We shared a lot of happy time during those days. He was very strong. Though in a wheelchair he insisted to do things by himself as far as he can. I brought him some coffee from lobby. First time, he took it; but second time he said he had to do more exercises to keep the strength of his muscle. Then suddenly I realized this is the way he survived with his illness. He was also a cute old man. In the lecture room, I sat next to him. From time to time, he fell sleep in his wheelchair during other speakers’ talks. It reminded me of some similar funny moments of my grandfather. During the break, Fred waked up and moved to the lobby, and was usually surrounded by young topologists. He was obviously the most popular man in the conference.    

Fred’s Phd student Yuxin Luo was also there at that time. We found a good Hongkong traditional restaurant nearby. And Fred suggested to have lunch there with his wife Kathleen and his post-doc Steven Amelotte. Prof. Paul Selick also joined us. He was working on Stephen’s exponent paper on 2-primary Moore spaces, and discussed with Fred about it from time to time. He even took Stephen’s paper to lunch. I am glad that he and Fred both enjoyed the food as they enjoyed math. 

In 2020-21, Fred and I worked together on a problem about configurations on graphs. He already guessed the right answer and we tried to work out the proof. During the collaboration, he wanted to use an old result of Wen-Tsun Wu, and accordingly recalled his visit to China in 1991-92. I quote several fragments of his words:

“A non-mathematical aside: In 1991-1992, I met Professor Wu at the Academia Sinca. I mentioned that I tried to find a copy of his book when I was a postdoc. One day later, I came to give a second lecture. Then Professor Wu gave me a signed copy of his book which I still have...”     

“... My father and I visited China in 1992. We went out to dinner with Professor Wu who wanted to try a Muslim restaurant.

My father also had a good friend named Ruth Chang. Her great great uncle was Chang Po-Ling the Founder of Nankai University. Ruth Chang's father had taught theatre arts at Nankai University. He had a secretary who was a young boy named Zhou En Lai. Ruth's sister married Shing Shen Chern. They had an interesting family.

One night we visited the home of Professor Chern on the campus of Nankai University. His home had a sign "The House of Geometry".

Unfortunately, we lost touch with Ruth Chang when my father became ill...”

We finished the project in early 2021. Fred suggested to think about further questions, and mentioned his book plan with his old friend Larry Taylor on cohomology computation of configurations. In Sep. 17, 2021, our only joint paper was accepted by Pacific Journal of Mathematics. During the publication process, I sent two emails to him for signing the copyright form, but got no response forever. In a homotopy conference held at that time, I learned from Jie Wu that Fred was in hospital. We thought he can get better as he did before. However, this time it is much worse... Since then, I got no news of Fred until he passed way in the morning of Jan. 16, 2022.     

Our last contact was at July 21, 2021. Fred asked me to suggest some referees for a paper he handled at AGT. He was still working at that time!

For me, Fred was a great example on math, life, friendship, and many other aspects. 

I kind of feel that...I lost grandfather once again.