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Hong Kong has six universities. I was surprised to learn that all of them are English-language universities, since while most educated people here speak at least some English, the lingua franca is certainly Cantonese. I am working at City University, which is in Kowloon, a few kilometers north of the main commercial/tourist area (although, to be honest, all of urban Hong Kong is commercial). Last week I visited Chinese University (CUHK), which is located about four subway stops north-westish of City U. The physics department there has the reputation of being the best among those at the six local universities, and in fact it has two Nobel Prizewinners associated with it – 1957 Laureate C. N. Yang, of Yang-Mills theory, is a “Distinguished Professor-at-Large,” and Charles Kao, who won in 2009 for the development of fiber optics, was a professor at CUHK for a while, and later the president of the university. Leo Lau, who spent some time at Western, was Chair of the physics department there, and later Dean of Science.

I didn’t know anyone there, however, so I resorted to perusing their web pages. I was pleased to find a prof there named Lei Xu, whose research interests were very similar to mine. I emailed him and politely invited myself for a visit. I spent a morning talking to him, looking around his lab(s), learning about his research and telling him about mine. I learned some useful things, which I’ll get a grad student to think about when I get home! I then went for lunch with several members of the department and a rather overwhelmed-looking young fellow who, it turned out, was there for a job interview.

There are other people in the department that I should also talk too, but they were busy with the job candidate the day I visited. It’s easy for me to go there again before I come home, though.

As an aside, I was interested to see a large statue of the “Goddess of Democracy,” who was made famous at Tienanmin Square twenty-three years ago, standing outside the University subway station. A sign next to it documented the problems experienced by this poor statue. Apparently she was a bit too controversial, and no-one, including the current University president, wanted to upset the Beijing government by hosting the statue. Eventually – with large support from the CUHK students and faculty, if not the senior administration – she was placed at the train station, where she is an impressive sight. 

As a physics professor I write a lot, and I also spend a lot of time editing other people’s writing. In fact, I would say that writing is probably the most important part of my job. Of course I have to be good at physics, and I have to have good ideas, and I have to keep beating on my students – pardon me, I mean constructively encouraging my students – to get things done, but none of this would get me anywhere if I couldn’t write about it. I think it’s also true that writing is an extremely important part of many other jobs that our students could find themselves in after leaving school – almost everyone has to write a report to their boss at some point. 

On the way to getting this job, I had to write a couple of theses, which are essentially full-length books about the research I did as a student. I need money to pay my students and to run my research operation, and to get money I need to write grant proposals. While the ideas and so on are very important, if I can’t express those ideas clearly in the written proposal, I shouldn’t expect to get funded. Once the research is done, I have to tell the world about it, and I do this by writing papers. It is a lot easier to get a paper published if it is well-written, and, more importantly, it is a lot easier for other scientists to read and understand a paper that is well-written. Since my ultimate success as a physics researcher depends on how other people regard my research, I am not going to be successful if I am unable to get people to read about my work.

My students have to write, too, and since I want my students to succeed, I try very hard to ensure that what they write is of high quality. This is sometimes very hard. I have had students who write very well, but I have also had students whose writing was awful. Sometimes language is an issue – it is obviously very difficult for someone to write a 300-page PhD thesis in their second language – but often there are problems that go beyond language. I have had students who were native speakers but had essentially no idea how to string sentences together to tell a coherent story. I had a student from China whose English writing was grammatically and structurally fine, but completely disorganized. That student told me that she was a poor writer even in her own language.

There are several aspects to writing. The first has nothing to do with the actual words: it is the ability to get the content right. On a large scale, this involves deciding what you want to say, what ideas you want to convey, essentially what the story is that you want to tell. On a smaller scale, you need to figure out what level of detail is appropriate, and you have to organize what you want to say: you need to decide in what order to present things so as to produce a clear and logical storyline. These are hard things to do, especially for one who has not done a lot of serious technical writing. One you know what you want to say, you need to write it down. Here you have to worry about the mechanics of writing – sentences and paragraphs, spelling and punctuation. This seems to be hard for some people, too, despite that fact that in this case there are usually rules that can be learned and, one hopes, followed. A third aspect involves getting the right style – a physics journal paper would be written in a very different style from a letter to your mom. In my view, the first aspect is by far the most important. It is relatively easy to edit a well-organized draft for grammar, punctuation, and even style, but it’s a lot harder to deal with a piece of writing that is poorly organized, is missing important information, or wanders through the subject matter like the random walks I talked about in my last post. 

I think it’s essential that our students learn how to write properly. I’m less certain how to achieve this. Certainly practice is essential, and for that reason I always assign essays or written projects in my third- and fourth-year courses and grad courses. But students need to get feedback on their writing if they are going to become good at it, and they don’t really get that until they start working on their honors thesis. Western has courses on technical writing, but there really isn’t any space in our modules for them. I’ve thought about teaching students to write in our seminar course, but it’s hard to make students do much work in a zero-credit course.

I’ll have more to say about this subject in future posts.

While in Hong Kong, I have been working with Jonathan Wylie on the theory of diffusion with “traps”. This is related to some of my experiments, and what we are aiming for is a way to extract some new physical information from our experimental measurements. The experiments involve measuring the diffusion of little tracer particles suspended in a complex fluids. For simple Brownian motion, the mean squared displacement increases linearly with time. In many complex fluids, we see something rather different: At very short times, the mean squared displacement increases linearly. Then over some intermediate time range, the mean squared displacement flattens out into a plateau. At longer times, it grows linearly again, but with a lower diffusion constant than at short times. The plateau occurs because the tracers get trapped by the microstructure of the complex fluid. However over longer times, the microstructure evolves and the particles can escape from the traps and diffuse freely again. The calculations we are doing – actually it’s mostly Jonathan so far – involve using the formal theory of random walks to figure out the distribution of distances traveled by the tracers in the presence of traps. The particles diffuse freely until they hit a trap, then they are held in the trap for a time drawn from a particular distribution, then they diffuse again. Parts of the calculation are straightforward, if you know about random walk theory. But parts are what you might call interesting. I have had to refresh my memory about Green functions, which caused me nightmares when I was a student and played a significant role in my decision to become an experimentalist. We have also run across one of those pathological cases that mathematicians warn us about, but which never happen in real life – we get an expression involving an integral over an infinite sum, and it turns out that you cannot interchange the order of the sum and the integral. All good stuff. The idea is that this will model our experimental data, and the ratio of the diffusion constants we find at short and long times will depend on the time the particles spend in the traps.