Friday, July 10, 2020

The discipline of scientific writing

Writing a paper is hard work. Writing a paper that is clear, engaging, and accurate is even harder. After you have written a draft or are reading a draft of a colleague or co-author I think the following discipline is important and worthwhile.

Go through every sentence and ask, is this true? Is it precise and accurate?

Let me illustrate with a concrete example. Consider the following different claims.

The experiments of Jones et al. proved that GaAs quantum wires are Luttinger liquids.

Jones et al. interpreted their experimental results on GaAs quantum wires in terms of the framework of Luttinger liquid theory.

Jones et al. fit their experimental data for the temperature dependence of the resistivity of a GaAs quantum wire to a power law, such as predicted by Luttinger liquid theory.

Jones et al. showed that their experimental data was inconsistent with Fermi liquid theory, but consistent with Luttinger theory.

Hopefully, the differences between these claims are clear.

This discipline becomes even more important when reporting one's own research. For example, just replace ``Jones et al." in the sentences above with "We".

Unfortunately, the rush to publish in luxury journals has increased the tendency of authors to not exercise the appropriate restraint and discipline required by scientific integrity.

Friday, June 26, 2020

The Classics matter

Some people might expect me to be enthused that the Australian government recently announced that the tuition costs for university degrees in the humanities and social sciences would increase and the costs of undergraduate degrees in mathematics and sciences has decreased. This is based on three unquestioned assumptions and values. First, university is a job-training program. Second, all these extra mathematics and science graduates will get employment in the area that they study. Third, there is no need to address the massive other problems that Australian universities are facing, further accentuated by covid-19.

The central purpose of a university education is to learn to think.

Why study the classics? Recently, I read the following letter to The Economist written by Robert Machado, a PhD student in classics at Cambridge.
As a teacher and researcher in classics, I care profoundly about the subject’s purpose (Johnson, May 2nd). Too many of my colleagues rely on the guff that it teaches grammatical rigour or fall back onto vague assertions about the origins of Western civilisation. Although it is good to have a knowledge of ancient societies, the study of classics or indeed any ancient peoples offers one important transferable skill. When studying any ancient civilisation, one quickly brushes up against the reality that 99.9% of the information one would like to have is already lost. This forces any student or researcher to reflect hard on what data can be used. We must carefully analyse and argue over every scrap, while avoiding the temptation to come to conclusions that the data do not justify. In an age where we are faced with a glut of data, knowing what they can or cannot be used to say is vital.
Rodney Stark was a well-established sociology professor at the University of Washington when he made the bold move to work on the history of early Christianity, making use of methods and concepts from sociology. In the Preface to his book, The Rise of Christianity, he notes
my effort to reconstruct the rise of Christianity has been a cherished hobby - a justification for reading books and articles that now fill an entire wall of my study. It would be impossible to express adequately how much pleasure I have gained from these authors. I am convinced that the students of antiquity are on average the most careful researchers and the most graceful writers in the world of scholarship. 
Parenthetically, I note that Stark's work and attitude provides a model of how to successfully break into a new field.

Wednesday, June 24, 2020

Why Josephson matters

Reflecting on macroscopic quantum effects in condensed matter I have come to the view that Brian Josephson is a key figure. But, the observation of magnetic flux quantisation in superconducting cylinders is also a landmark.

The significance of Josephson is nicely laid out in a fascinating article published by in Physics Today in 2001 by Donald G. McDonald
John Bardeen, the leading condensed matter theorist of his day, was quite wrong when he dismissed a startling prediction by the unknown Brian Josephson. 

The article nicely lays out several important precursors to Josephson's work that all occurred after BCS theory in 1957.

1. The experimental (unanticipated) discovery by Ivar Giaever in 1960 of single-particle tunneling in SIS junctions [superconductor-insulator-superconductor sandwiches]. I-V curves clearly showed the structure of the BCS energy gap.
[Aside. This discovery was also laid the foundation for John Rowell's tunneling experiments that allowed a quantitative (strong-coupling BCS) analysis of the electron-phonon interaction responsible for superconductivity.]

2. The discovery by Hans Meissner [not the discoverer of the Meissner effect!] in 1960 of the proximity effect, where superconductivity is induced in a non-superconducting metal, by close proximity to a superconductor.

3. The discovery in 1961 by two independent experimental groups that the magnetic flux inside a cylinder was quantised in units of h/2e where h is Planck's constant and e is the electronic charge. This effect had been predicted by Fritz London in 1948.
These experiments provided ``the first direct demonstration of a macroscopic quantum effect.''
Aside. These experiments also clearly showed the physical nature of the magnetic vector potential, A, and illustrated the Aharonov-Bohm effect.

4. Josephson's attendance at a series of lectures ``Concepts in Solids" that Phil Anderson gave to graduate students at Cambridge in 1961-1962. In particular, at the end, Anderson introduced the concept of broken symmetry as an organising principle to describe ``condensed systems" such as antiferromagnets, superfluid 4He, ferroelectrics, and superconductors.

Distinctly quantum phenomena are tunneling, superposition (and the associated coherence and interference), and entanglement. Josephson junctions can be used to illustrate all of these at the macroscopic scale.

This is explored in a nice autobiographical article by Tony Leggett.
Because of the strong prejudice in the quantum foundations community that it would never be possible to demonstrate characteristically quantum-mechanical effects at the macroscopic level, this assertion made us [Leggett and Garg] the target of repeated critical comments over the next few years. Fortunately, our experimental colleagues were more open-minded, and several groups started working toward a meaningful experiment along the lines we had suggested, resulting in the first demonstrations (29, 30) of MQC [Macroscopic Quantum Coherence] in rf SQUIDs (by then rechristened flux qubits) at the turn of the century. However, it would not be until 2016 that an experiment along the lines we had suggested (actually using a rather simpler protocol than our original one) was carried out (31) and, to my mind, definitively refuted macrorealism at that level. I find it rather amusing that nowadays the younger generation of experimentalists in the superconducting qubit area blithely writes papers with words like “artificial atom” in their titles, apparently unconscious of how controversial that claim once was.

Thursday, June 18, 2020

The lecture Feynman really wanted to give to undergraduates

For Condensed Matter Physics: A Very Short Introduction, I have started writing a chapter on "Quantum matter". It is a challenge to decide what to include, particularly given how the content needs to be accessible to a general audience. The question, "What is quantum matter?" is an interesting one. Currently, I have decided to focus on how superconductors and superfluids can exhibit macroscopic quantum effects. More on that later. 

In the process, I was reminded of the last lecture in the celebrated Feynman Lectures on Physics. These are now available online, including photos.

The Schrödinger Equation in a Classical Context: A Seminar on Superconductivity

Here is Feynman's introduction to the lecture, given on June 4, 1964. This was the last lecture in a two-year ``introductory" physics course for Caltech undergraduates.
This lecture is only for entertainment. I would like to give the lecture in a somewhat different style—just to see how it works out. It’s not a part of the course—in the sense that it is not supposed to be a last minute effort to teach you something new. But, rather, I imagine that I’m giving a seminar or research report on the subject to a more advanced audience, to people who have already been educated in quantum mechanics.

All that aside, this is a subject I want to talk about. It is recent and modern and would be a perfectly legitimate talk to give at a research seminar. My subject is the Schrödinger equation in a classical setting—the case of superconductivity.
The lecture includes a description of the quantisation of magnetic flux, the Josephson effect, Shapiro steps, and a SQUID. All of these phenomena had only been discovered in the two years before the lecture. It is striking that Feynman clearly appreciated the significance of these recent discoveries, not just for condensed matter but also for quantum theory. He concludes the lecture as follows.
These then are some illustrations of things that are happening in modern times—the transistor, the laser, and now these junctions, whose ultimate practical applications are still not known. The quantum mechanics which was discovered in 1926 has had nearly 40 years of development, and rather suddenly it has begun to be exploited in many practical and real ways. We are really getting control of nature on a very delicate and beautiful level.

I am sorry to say, gentlemen, that to participate in this adventure it is absolutely imperative that you learn quantum mechanics as soon as possible. It was our hope that in this course we would find a way to make comprehensible to you at the earliest possible moment the mysteries of this part of physics.

Tuesday, June 16, 2020

Taking a break from it all

Covid-19 and the associated fallout marches on. Increasing attention is being given to the impact of social isolation (sheltering in place) on mental health. Finally, it caught up with me. This is in spite of my personal situation and that in Australia being relatively easy. Almost immediately when I moved my office to home I started having significant neck and back problems. I made six trips to the physiotherapist over the course of four weeks, carefully monitored my posture, did exercises, and limited my sitting time. I got better. But, I know wonder how much was psychosomatic. I pretty quickly got zoom fatigue. Then a few weeks ago I started to see other mental health warning signs, particularly being easily overstimulated and anxious. I was disappointed because I thought I was managing it relatively well. 

So I bit the bullet. I took 9 days off work and never looked at email.
Social distancing requirements are now relaxing in Australia and we are now allowed in-state travel. My wife and I (and Priya the dog) went to our favourite Queensland holiday destination Bribie Island for a week. (This is also the location of the photo from my blogger profile). It was wonderful. Here are a few photos. I also saw some dolphins really close to the shore!

I also had a phone appointment with my psychologist who challenged me to restart mindfulness exercises. I am also trying to keep on top of the basics (sleep, diet and healthy fluid intake, exercise, limited screen time, reducing stress, ...)
So, do not under-estimate the impact of covid-19 on your mental health. Once you get a chance take a break.

Feel free to share your own experiences and/or relevant articles.

Wednesday, May 27, 2020

The 90% University

A helpful starting point for me when considering universities after the pandemic is the cover story of The Economist, from two weeks ago, The 90% Economy. They were reflecting on the world economy will change in the coming years, suggesting three key characteristics.

 1. the economy will be more fragile 
 2. there will be less innovation thirdly 
 3. there will be even greater inequality 

The reason that it is called the 90% economy because in the next few years rather than growing a few percent each year it will decrease in size by about 10%. 
Now on one level that doesn't sound too bad, but the problem is that it is not a uniform decrease across every sector, company, and individual. The changes will be quite heterogeneous. Rather, there will be significant gaps, that because of the interconnectedness of everything there will be problems. 

Just like the economy going back to ``normal'' universities will continue to have students, continue to do teaching, continue to graduate people but things, won't be quite the same, in some quite significant ways. It is not just a matter of possible 10-20 percent budget cuts.

1. Universities will be more fragile

Less stability and predictability is particularly bad for universities. Key ingredients for universities to achieve their real purpose are time and stability. Significant research, teaching, and learning all require time to build up knowledge, explore different possibilities, make mistakes, and not be distracted by crises, whether personal, institutional, or societal. Economic uncertainty is just one of many dimensions to the forthcoming fragility.

2. There will be less innovation in universities

Research is all about innovation, discovering new things, and exploring new ideas.  Drawing on The Economist article. More virtual meetings, less international travel, and less face to face meetings means less brainstorming. Less random meetings and informal interactions will mean fewer new ideas. There will also be less money available for discretionary funding for new initiatives and less startup funds for new faculty, even if hiring freezes end.
After any crisis people are more cautious and more risk-averse. A problem before the pandemic was that science was increasingly being done in a very risk-averse manner. People, particularly those without tenure, focus on low-lying fruit, working on problems that they are pretty sure they can solve in a year or less. Even senior people can only get funding if they have a ``track record'' in an area. This means they will just keep doing the same thing and not move into new areas. 
In reviewing his scientific life, Tony Leggett recently made the following comments.
Indeed, when I look back on ... a 60-year career in physics, I think I have been fortunate in many ways. I have had a marvelous constellation of graduate students and postdocs, from all corners of the globe... But if I had to pick out one thing that made all the difference, particularly in the early stages, it would be the tolerant and relaxed environment that I experienced at Sussex when starting there in the late 1960s. When I recall this and then look around at the current environment for people at the postgraduate, postdoc or junior faculty level, I feel quite concerned ... I get the impression that many of them feel that there will be no hope of obtaining the kind of postdoctoral/faculty/tenured position .. unless they have not only published three or four papers but published them in high-impact journals... I fear that one almost ineluctable outcome is that there is a strong temptation to focus all one’s energy on problems that can be reasonably guaranteed to yield results within the relevant time frame, typically two or three years. And almost by definition, these are not the really worthwhile problems! ...  the best advice I can give to any younger colleagues who seek my opinion is deliberately to put aside some fraction (30%, 25%, even 20%) of their research time for problems that they not only are not sure they can solve within the two- or three-year deadline but are not even sure that they (or anyone) can solve at all.
A similar conclusion can be drawn from a brilliant podcast, The Obscure Virus Club, by Malcolm Gladwell.

3. There will be more inequality, both within universities and between universities

This is part of the social tragedy that the rich get richer and the poor get poorer, particularly during and after a crisis, such as a pandemic. The poor do not have the resources to adapt and survive. If you live in a slum you can't practice social distancing. If you don't have access to clean running water or disinfectant it is hard to practice personal hygiene.  If you lose your job you can't use your savings to go and get training for a new job. In contrast, if you are wealthy and have significant cash reserves you can wait things out, see your competitors fail, and snap up cheap investments. Similarly, with universities it's hard for me to believe that institutions such as Harvard with massive endowments won't come out of the pandemic relatively stronger. Weak institutions will fold. Others will really struggle to survive and go through periods of stagnation.

There will also be inequality within institutions related to access, gender, and seniority. Because of the background of an economic downturn it will be harder for students from poorer backgrounds to afford tuition or access scholarships. Furthermore, poor job prospects will make the financial cost and risks of student loans not seem worthwhile. There will also be a push within universities to increase the number of adjunct faculty (i.e. people on short term teaching contracts with no benefits). People with tenure who are well established will do fine because they also have a good strong social and professional networks. In a more online environment it's harder to build those professional networks and so disparities may increase. The Economist article mentions a study that found the productivity of female economics faculty, as measured by the production of research papers, fell relatively to male ones, since the pandemic. That's arguably because women are more likely to have to take care of homeschooling and entertainment of bored children during the lockdown.

All this is a bit depressing. However, with a crisis there are always opportunities. There will be plenty of opportunism (where people exploit a situation without regard to moral considerations and the impact on others). But, there will also be opportunities for the wealthy, powerful, and privileged to do good and facilitate much-needed changes in universities. For example, large philanthropies and wealthy universities can make long term investments that others won't or can't. Well established faculty can provide support/cover to junior faculty, students and postdocs. In the longer term of decades, these will likely be the institutions and individuals at the forefront of what universities really should be about.

Monday, May 25, 2020

The Critical Point

I have now finished my first draft of chapter 6, of Condensed Matter Physics: A Very Short Introduction. The main purpose of the chapter is to introduce the idea of the critical point and the renormalisation group.

 I welcome comments and suggestions. However, bear in mind that my target audience is not the typical reader of this blog, but rather your non-physicist friends and family.

I think it still needs a lot of work, particularly to be less technical.

The goal is for the chapter to be interesting, accessible, and bring out the excitement and importance of condensed matter physics.

Aside. Don't think that because I am posting two chapters one week apart that I am writing one per week. I wish I could. I sometimes move onto a new chapter before getting it into a draft form good enough to post.