Monday, 2 July 2012

Rila Mountain Workshop & Chaos

Last week, I was in the Rila Mountains in Bulgaria for a nuclear physics workshop.  Like ever, I find myself newly-invigorated with the fun of doing research, talking about it, and finding out what other people are getting up to.  The picture in the post is the view from the conference room, on those rare occasions when my attention was not fixed on the speaker.

There were two talks about the link between quantum chaos and nuclear spectra.  Quantum chaos is nothing but the quantum analogue of classical chaos, in which, for example, two trajectories in a dynamical system with very similar starting points will diverge in behaviour in later times, no mater how similar the starting positions.  This makes the future behaviour of such systems hard to predict, as even though the equations are deterministic, the ability to measure the starting point with infinite accuracy is not possible.  This is one reason why weather forecasting is so hard.

In quantum mechanics, most systems are not quite like this.  We don't necessarily talk of trajectories, and starting positions may not necessarily be allowed to be close together thanks to quantisation.  In nuclear physics, the normal language of quantum chaos is in terms of the statistical spacing of energy levels and not much to do with trajectories.  In nuclei, this energy level spacing agrees with the predictions of random matrix theory, suggesting some chaos in the underlying nuclear force.  A few years ago I tried to do some work on the link between chaotic motion in nuclei using a kind of quantum theory which had a semiclassical aspect to it, which showed both classical chaos in its semiclassical trajectory and quantum chaos in its spectrum.  I thought I had at least hinted, in making this link, at something profound, but the referees didn't think so.  I ended up including it in a lightly-refereed conference proceeding, which has been lightly-cited since, but listening to the talks made me think I should pick up the subject again.

Since the conference has finished, I've been having a holiday in Plovdiv, Bulgaria's second city.  I'm going home tomorrow, but I'll be a bit sad to leave.  The weather is nice, it's a nice city and the beer is cheap.  But all good things must come to an end...