Monitoring blog traffic

Google Analytics provides any easy way to track traffic on your web page or blog. This blog normally gets about 40-80 page views per day. Certainly, enough to encourage me that there is enough interest that it is worth my effort. But, I got a bit of a shock when I last checked. Here are the number of page views for the past week:

Monday 70

Tuesday 91

Wednesday 159

Thursday 369

Friday 1877

Saturday 326

Sunday 117

Why the spike centered on Friday? It seems the post on the Nature paper using 17 parameter fits was featured by Hacker News, producing 1300 hits. I was impressed that they went back and read my earlier posts about curve fitting, particularly the Nature article by Freeman Dyson about getting the elephant's trunk to wiggle.

The cartoon is from a Physics Today article, Encouraging good science on the web, by Alexander Antunes.

Quantum dynamics of nuclei

John Negele wrote a really nice Physics Today article in 1985 on the role of mean-field theory in nuclear physics.

Ideas discussed include:

-nuclei are small drops of a dense, strongly interacting quantum liquid

-why the success of mean-field theory is astonishing

-but it works because of Landau's Fermi liquid theory

-in nuclei the density varies smoothly (they are not billiard balls)

-instantons (imaginary time trajectories) provide a natural way to describe tunneling effects such as fission and fusion

-the effective nucleon-nucleon interaction is density dependent

-as the density of nuclear matter increases the effective interaction increases and neutrons can escape the nucleus and form a "gas". this is what happens in neutron stars

I have been reading this in preparing for the visit of Cedric Simenel to UQ this week. I am looking forward to hearing his seminar which will feature the picture above and discuss significant advances in dynamical simulations since Negele's article.

What resources make a great teacher?

Believe it or not, this post was inspired by a stirring (and amusing) piece, Beware the ego trip, by columnist Kathleen Noonan in Brisbane's tabloid newspaper. The relevant bit for readers of this blog is the reference to an article in the Atlantic Monthly, What makes a great teacher? Noonan summarises:

More than any other variable in education - more than schools or curriculum - teachers matter.

First, great teachers tended to set big goals for their students. They always were looking for ways to improve their effectiveness. Great teachers constantly re-evaluate what they are doing.

Great teachers had four other tendencies in common: they avidly recruited students and their families into the process; they maintained focus; they planned exhaustively and purposefully - for the next day or the year ahead - by working backwards from the desired outcome; and they worked relentlessly, refusing to surrender to poverty, bureaucracy and budgetary shortfalls.

The other thing that predicted success in the classroom was . . . wait for it . . . happy teachers. Teachers who scored high in "life satisfaction" were 43 per cent more likely to perform well in the classroom than their less satisfied colleagues. Their zest and enthusiasm spreads.

University middle managers should take note.

Desperately seeking spin liquids III

It was wonderful having Bruce Normand visit UQ this week. It is great having a visitor come who meets individually with students, postdocs, and faculty and discusses their work at length. I think we all learnt a lot and appreciated the constructive feedback.

Bruce made me aware of a nice accessible review Frontiers in frustrated magnetism that he just published in Contemporary Physics.

The focus is on spin liquids: whether they exist in real materials and/or Heisenberg lattice models. This gives more background relevant to a conjecture I discussed in two previous posts. From Bruce's seminar and discussions I now realise there is a strong candidate counter-example to the conjecture. That is the Heisenberg model on the isotropic triangular lattice with multiple spin exchange. The best numerical evidence of a spin liquid (unbroken lattice symmetry, spin gap) is in this paper. It would be great if more numerical work was done on this model using new methods such as those based on tensor-network states.

The challenge of science journalism

Nature publishes 17 parameter fits to 20 plus data points

Today's issue of Nature has a paper which features the Figure above. According to the Supplementary Material the curves shown involve 17 free parameters. The authors showed me a draft of the paper and I pointed this out to them. It was this experience which inspired the "curve fitting" posts on this blog.

Alternative quasi-particles in nuclei

Describing a nucleus with quantum many-body theory is a fascinating and challenging problem with a long history. Previously I wrote about the highly successful shell model which treats the nucleons as weakly interacting with one another.

A complementary approach for nuclei with an equal even number of protons and of neutrons is to view the basic "quasi-particle" as an alpha particle (a bound set of 2 neutrons and 2 protons). This takes into account some aspect of the strong short-range interactin between nucleons. A really nice accessible review by Martin Freer is worth looking at (especially figures 1, 4, and 5). This gives a natural description of the Hoyle state, "The importance of this state is arguably unparalleled in nuclear science." [In order to explain stellar nucleosynthesis of carbon, Sir Fred Hoyle successfully predicted the existence, energy, and quantum numbers of this state in carbon.]

There is a nice Physics article by Michael Carpenter which considers Do alpha particles cluster inside heavy nuclei? and gives a viewpoint on a recent PRL showing evidence for a alpha + 208Pb state in 212Po.