A simple question

Here’s a question that generated a lot of interest among the people involved in my metals and superconductors short course.

The question is this: Is Newton’s second law – that the net force on a body is equal to its mass times its acceleration – simply a mathematical definition of what a force is? Or is there some additional physical content? If so, what precisely is that content?

Some people regard the answer to this question as “obvious”. As is often the case with interesting questions, one person’s “obvious” may be another person’s “wrong”, so I’d be interested to hear other people’s opinions. If I have time (very busy the past couple of weeks) I’ll put together my own best understanding of the answer.

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Lectures on Metals and Superconductors

PDF lecture notes for an informal seminar series on metals and superconductors. Files are typically 10-20 pages long, and between 1 and 2 megabytes, with a few somewhat larger files.

Part I: The Drude Theory of metals

Lecture 1: Introduction to the Drude theory of metals
Lecture 2: Applications of the Drude theory
Lecture 3: AC electrical conductivity of a metal
Lecture 4: Thermal conductivity of a metal

Part II: The Sommerfeld theory of metals

Lecture 5: Ground state properties of a free electron gas
Lecture 6: The Fermi-Dirac distribution
Lecture 7: Energy density and specific heat in a free electron gas
Lecture 8: The Sommerfeld model of metals

Part III: Superconductivity

Lecture 9: Superconductivity: basic facts

Lectures on Metals and Superconductors

PDF lecture notes for an informal seminar series on metals and superconductors. Files are typically 10-20 pages long, and between 1 and 2 megabytes, with a few somewhat larger files.

Part I: The Drude Theory of metals

Lecture 1: Introduction to the Drude theory of metals
Lecture 2: Applications of the Drude theory
Lecture 3: AC electrical conductivity of a metal
Lecture 4: Thermal conductivity of a metal

Part II: The Sommerfeld theory of metals

Lecture 5: Ground state properties of a free electron gas
Lecture 6: The Fermi-Dirac distribution
Lecture 7: Energy density and specific heat in a free electron gas

Recruiting PhD students

How ethical/sensible is it to take on large numbers of PhD students?

The question has been on my mind, as my last week was spent helping organize a “Postgraduate information and recruitment day”, with the event itself held last Friday.

We brought eight potential PhD students from outside UQ into the Department of Physics, and gave them lots of chances to mix with the various research groups.

It was a fun day for all, and hopefully we’ll end up with some great new PhD students as a result.

It also returned to the forefront of my mind some ethical questions about taking on PhD students.

Traditionally, PhD degrees in many of the Arts and Sciences have focused almost entirely on preparation for a career in academic research or teaching.

(Incidentally, much of what I say below does not apply to professional postgraduate degrees, such as are found in many Engineering and Business Departments, which often have a substantial focus on the so-called real world.)

The stereotypical “ultimate success” story in such degrees is of the PhD student who writes lots of papers and becomes a bigshot Professor, with many students of their own.

Conversely, there is a slight stigma associated with people who don�t get postdoctoral positions (or, similarly, postdocs who don�t get tenure-track positions, and so on up the chain), who leave to go into industry, or who leave their field altogether. A not unusual presumption is that a person who does this has �failed�. People speak of it with regret, with pity, or, surprisingly often, with disapproval or even scorn.

Of course, the bigshot Professors typically have many PhD students, sometimes as many as dozens over a career. As a result, either the number of academic positions needs to expand at an incredible rate � which it did for several decades after World War II (perhaps the reason for our current culture), but is not doing any longer – or a heck of a lot of students are going to �fail� according to now-current criteria.

This, in my opinion, is an appalling situation. What can be done about it?

As I see it, there are two broad options. The first option is to change the culture so that �success� for a PhD student is redefined in an expanded way. The second option is to greatly reduce the number of PhD students.

I�ll talk briefly about how each of these options might be taken, before making a comparison. The pictures I paint are perhaps somewhat unrealistic, partially because of the brevity, and partially because of my incomplete knowledge. Nonetheless, I think the pictures I sketch here might serve as a useful basis for improving the PhD experience.

How might we expand the definition of success for PhD students?

Imagine that each semester PhD students are given the option of working, one day per week, as consultants on a variety of real-world projects, for real companies.

A student who spends perhaps two or three semesters so engaged might work on five or six such projects, and might make 20-30 contacts at a dozen or more companies.

Such students would get a good sense for how their skills may be applied in the real world, and for much they�d enjoy doing such work, as compared with research. They�d gain confidence that they can succeed in such an environment. Perhaps most important, they�d gain a sense that they can go out and get themselves jobs � and they�d have a starting list of contacts to help them get jobs.

I believe such a consulting scheme would have the further benefit of greatly reducing the stigma associated with not going on with a career in basic research. The people doing postdocs and searching for faculty posts would be doing so fully informed of the alternatives available to them. In short they�d be making a conscious choice to take the academic route. This would both reduce the number of people searching for academic positions, and improve the quality of life for all involved.

A variety of objections may be raised to such a consulting scheme.

Could such a consulting scheme be operated across all disciplines?

In some disciplines, such a consulting scheme could almost certainly be operated. I�ve never consulted, but am reliably informed that a lot of consulting work is available for physicists, if one knows who to talk too.

What about other disciplines? Certainly, in many disciplines it is easy to see such schemes being practical. Mathematics, chemistry, biology and economics, for example, should all offer ample opportunities.

Other disciplines might be more difficult. It is not so obvious what consulting opportunities would be available to PhD students studying mediaeval history, or the romance languages. Nonetheless, such students often have fine writing, communication and analytic skills � skills that are in high demand. It is possible � though I don�t know � that consulting opportunities could be organized for such students. If not, then I have few suggestions to make, other than to reduce the number of PhD students in such programs. This option is described in more detail below.

Won�t such a consulting scheme distract the students?

Most Universities currently allow their students to work 1-2 days per week as tutors or teaching assistants. If they gave them the option of working as tutors / teaching assistants or doing consulting, but not both, this ought to alleviate any difficulties with distraction.

Won�t this leave too few tutors or teaching assistants to teach into Departmental courses?

This might be a problem, but could easily be alleviated, perhaps by restricting the pool of students allowed to engage in the consulting work � perhaps only second year PhD students would be allowed to do it.

Won�t it be much more financially attractive for students to consult than to tutor?

It might. On the other hand, a portion of the consulting fee might be used to increase rates for tutors, in order to achieve pay parity.

Who would organize the consulting?

If the Department takes a small percentage of the total consulting fees paid, then they ought to be able to pay somebody, at least part time, to co-ordinate the consulting program.

Might a Department end up exploiting their PhD students to make lots of money?

This would be something to guard against. You could imagine a horror situation where the primary role of grad students in some exploitative Departments is to engage in consulting jobs to fund faculty research. A way of preventing this would be to put severe restrictions on how income raised from consulting could be spent. It might be restricted to spending, for example, on improving student conditions, such as offices, travel, and access to computer equipment.

The other option for improving the PhD experience identified earlier is to reduce the number of PhD students. How might this be achieved?

This is a more difficult option to act on directly, because it is bound up with high-level institutional issues. (Unless, of course, one has a lot of influence at the highest levels! I�m taking the perspective of an individual faculty member here.)

Many Universities, certainly in Australia, but also around the world, provide significant incentives � both carrot and stick � to increase the number of PhD students. For example, Department, School, Faculty and University-wide funding is often directly linked to the number of PhD students. This leads to considerable pressure on individual academics to take large numbers of PhD students.

Combined with these institutional incentives, of course, is the natural desire that many academics have to create large and vibrant groups of their own.

For these reasons, my inclination is to work the other end, concentrating on changing the culture so that PhD students are given the opportunity to voluntarily engage in a small amount of non-academic work.

This leaves a final challenge, which is what to do in those fields where there is little demand for the services of PhD candidates, outside of an academic context. In that case I think the difficulties are far more formidable, and will require difficult long-term transformations, in both faculty and institutional attitudes and funding models, so that large research groups are not seen as an unalloyed good, but rather where the decision to take PhD students is made extremely carefully and cautiously.

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