Decoherence in nuclear physics

Following up on my previous post and looking forward to extensive discussions with Nanda Dasgupta, David Hinde, and Gerard Milburn over the next two days. Here are some of the questions we are trying to answer:

What internal nuclear degrees of freedom are the source of decoherence in nuclear scattering?
Excited states? Giant dipole resonance? Particle transfer?

Usually one describes the environmental degrees of freedom in terms of a spectral density. What dependence does this have on frequency and the internuclear separation?

What would be a smoking gun experiment to show the presence of decoherence? We want to show how increasing decoherence washes out quantum interference effects. Mott scattering of identical nuclei may be relevant?

What is the relationship between the decoherence which suppresses quantum tunneling and inelastic processes?

A new party trick?

Todays lecture went pretty well. There were lots of questions. The students love the video demonstration of ice regelation. They said cutting through the ice with a wire would be neat party trick. I looked on Youtube but the only video I could find was this one. Let me know if you find them a better one.
Here is tomorrows lecture, as it stands.

How I came to love nuclear physics

About 18 months ago Gerard Milburn and Phil Stamp invited me to a small PITP workshop in Vancouver on Quantum Information and Many-body Physics. It was there that I met David Hinde and Nanda Dasgupta from Nuclear Physics at ANU (where I was an undergraduate). The talks given by David and Nanda were about a beautiful series of experiments that measure with incredibly high resolution the energy dependence of the cross section for nuclear fusion of two colliding complex nuclei. For fusion to occur quantum tunneling below the potential energy barrier between the nuclei must occur. This is found to be suppressed compared to what is expected for reasonable nuclear potentials and in a PRL with Gerard and a later theory paper with Alexis Diaz-Torres they suggest this suppression is because of decoherence arising from interaction of the relative motion of the nuclei with the internal degrees of freedom of the nuclei. I had been thinking a lot about quantum tunneling of protons in enzymes and reading the theory of quantum tunneling in the presence of a dissipative environment. What really got my attention was the quality of their data which extended over 8 orders of magnitude of the tunneling probability!


This should provide significant constraints on any theory for tunneling in the presence of decoherence. Nanda will give the physics colloquium at UQ this Friday.

How much of physics is condensed matter physics?

Of the 108 physicists who are most highly cited (ISI Highly Cited.com) for papers published in the period 1981-1999, about 2/3 are condensed matter physicists (26 theorists and 47 experimentalists).

In the past 23 years the Nobel Prize in Physics has been awarded 11 times for work on condensed matter.

In the past 10 years the Nobel Prize in Chemistry has been awarded twice to condensed matter physicists!

Some of my favourite phase diagrams

Tomorrow's lecture is on phase diagrams. I like the students to realise that there is a lot more to it than just solid, liquid, and gas. So I show them diagrams like these.


I got that here.




I got that here.

This is the lecture I gave last year. The demo videos (which you can't see, sorry) are from the The Video Encyclopedia of Physics Demostrations, which the students love.

Am I a psychic or a theoretical physicist?

Although my family does not have a TV we have recently become addicted to watching DVD's of old episodes of The West Wing. This scene from Season 2, Episode 3, got a few laughs.

20 key concepts in thermodynamics and condensed matter

I have just finished revising my lecture for monday 9 a.m. I will mostly review my slant on 11 key ideas from thermodynamics. I will then just flag 9 key ideas that I hope I will be able to teach the students during the next 6 weeks (13 lectures, 4 tutorials). Any feedback is welcome.