Condensed concepts

My UQ economics colleague John Quiggin has an excellent article, Tell 'em there dreaming. He argues convincingly that nuclear power is irrelevant to reducing carbon emissions in Australia. The argument is purely pragmatic. We currently have no commercial nuclear power plants, no nuclear industry, and no legislative or regulative framework. Even in the most optimistic scenario [including the highly unlikely prospect of a groundswell of popular and political support for an ambitious nuclear program] it would be around 2040 before any actual electricity would come onto the grid. That is too late. Aside: the title of the article is an allusion to a famous line in a cult classic Australian movie, The Castle. If Americans want to really appreciate that Australia is a very different culture they should watch this movie with a group of Australians. The Aussies will be dying with laughter and the Americans will be wondering what is so funny.

Increasingly I see people show slides like this in talks. I don't see the point. It is just a screen dump of a publication list from a CV. There is no pedagogical value. It is just saying, "Look, I have published lots of papers!" Don't do it.

Based on anecdotal evidence I fear/suspect that metrics, luxury journals, and funding pressures have led to a shift in how some/many of the best researchers operate. Thirty of more years ago the best researchers would operate as follows. They would pick a difficult problem/area, work on it for a few years and when they had (hopefully) solved it they would write a few (1-3) papers about it. They would then find some challenging new problem to work on. Meanwhile lesser researchers would then write papers that would work out more of the details of the first problem. Now, people want to work on lower risk problems with guaranteed steady "outputs". Thus, they are reluctant to "move on", particularly when they have a competitive edge in a new area. It is easy for them to churn out 10-20 more papers on natural "follow up" studies working out all the details. They are "safe" projects for graduate students. These papers may be valuable but they could

I was quite excited when I saw the picture above when I recently visited Susanta Mahapatra . One of the key predictions of the diabatic state picture of hydrogen bonding is that there should be an excited electronic state ( a twin state ) which is the "anti-bonding" combination of the two diabatic states associated with the ground state H-bond. Recently, I posted about how this state is seen in quantum chemistry calculations for the Zundel cation. The figure above is taken from Optimal initiation of electronic excited state mediated intramolecular H-transfer in malonaldehyde by UV-laser pulses  K. R. Nandipati, H. Singh, S. Nagaprasad Reddy, K. A. Kumar, S. Mahapatra The figure hinted to me that for malonaldehyde the twin state is the S2 excited state, because of the valence bond pictures shown at the bottom of the figure and because the shape of the two potential energy curves is similar to that given by the diabatic state model. Below I have plotted the curve

Hooray for Carl Caves! He has an excellent piece The High-impact-factor syndrome on The Back Page of the American Physical Society News. Before giving a response I highlight some noteworthy sentences. I encourage reading the article in full, particularly the concrete recommendations at the end. .... if you think it’s only a nightmare,.... , you need to wake up. Increasingly, scientists, especially junior scientists, are being evaluated in terms of the number of publications they have in HIF journals, a practice I call high-impact-factor syndrome (HIFS). I’ve talked to enough people to learn that HIFS is less prevalent in physics and the other hard sciences than in biology and the biomedical sciences and also is less prevalent in North America than in Europe, East Asia, and Australia. For many readers, therefore, this article might be a wake-up call; if so, keep in mind that your colleagues elsewhere and in other disciplines might already have severe cases. Moreover, most physic

This post concerns what may be the fast known internal conversion process in a chemical system, non-radiative d ecay times in the range of 3-8 femtoseconds . Internal conversion is the process whereby in a molecule there is a non-radiative transition between electronic excited states (without change in spin quantum number). This is by definition a break-down of the Born-Oppenheimer approximation. Much is rightly made of  the fascinating and important fact that excited states of DNA and RNA undergo "ultra-fast" non-radiative decay to their electronic ground state. This photo-stability is important to avoid mutations and protect genetic information. Conical intersections are key. The time scale for comparison is the order of a picosecond. The figure below is taken from Quantum Mechanical Study of Optical Emission Spectra of Rydberg-Excited H3 and Its Isotopomers   Susanta Mahapatra and Horst Köppel It shows the wavelength dependence of the intensity of emission

Stefan Grimm was a Professor of Medicine at Imperial College London. It was deemed by his supervisors that he was not bringing enough grant income into his department. Tragically, he was later found dead at his home. Email correspondence from Grimm and from his supervisors has been made public on a blog. It is very sad and disturbing. This was my first encounter with this excellent blog DCs Improbable Science written by David Colquohoun FRS, Emeritus Professor of Pharmacology at University College London. He also has an interesting post that is rightly critical of an Australian universities for taking millions in "research funding" from dubious vitamin, herb, and supplement companies. He also has important posts exposing  metrics and hype in luxury journals.

In a quantum many-body system a key thermodynamic quantity is the charge compressibility, the derivative of the charge density with respect to the chemical potential d n/d mu. In a degenerate Fermi gas kappa is simply proportional to the density of states at the Fermi energy. kappa is zero in a Mott insulator. As the Mott transition is approached, the behaviour of kappa is non-trivial. For a band width (or frustration) controlled Mott transition that occurs at half filling, Jure Kokalj and I showed how kappa smoothly approached zero as the Mott transition was approached. However, there is some debate as to what happens for doping controlled transitions, e.g. does kappa diverge as one approaches the Mott insulator. One thing I had wondered about was how one actually measures kappa accurately in an experiment. Varying the chemical potential and/or charge density is not always possible or straightforward. See for example, Figure 10 in this review by Jaklic and Prelovsek , which comp

Occasionally I have to write a paragraph or two about why condensed matter physics is important in the Australian context, where it is arguably under-represented. Here is my latest version. Condensed matter physics is one of the largest and most vibrant areas of physics.  1. In the past 30 years the Nobel Prize in Physics has been awarded 13 times for work on condensed matter.  2. Since 1998 seven condensed matter physicists [Kohn, Heeger, Ertl, Shechtmann, Betzig, Hell, Moerner] have received the Nobel Prize in Chemistry!  3. Of the 144 physicists who were most highly cited in 2014 for papers in the period 2002-2012 (ISI highlycited.com), more than one half are condensed matter physicists.  4. The largest physics conference in the world is the annual March meeting of the American Physical Society. It attracts almost 10,000 attendees and is focused on condensed matter.  Many of the materials first studied by condensed matter phy

Only last week I realised that an important and profound property of emergent quantum matter is the emergence of new length scales. These can be mesoscopic - intermediate between microscopic and macroscopic length scales . Say, very roughly between 100 nanometers and 100 microns. Previously, I highlighted the emergence of new low energy scales in quantum many-body physics. The energy and length scales are often related. In or near broken symmetry phases, some emergent length scales can be related to the rigidity of the order parameter  such as the spin stiffness. An example is the superconducting coherence length , xi which determines the minimum thickness of a thin film required to sustain superconductivity and the size of vortices in a type II superconductor . It is roughly given by  xi ~ hbar v_F/Delta ~ a E_F/Delta where v_F is the Fermi velocity, Delta is the energy gap, a is a lattice constant, and E_F is the Fermi energy. Since in a weak-coupling BCS superconductor Delta

Here are the slides  for my talk at todays workshop on grant writing for the School of Mathematics and Physics at UQ. A rough outline of the talk, with links to relevant earlier posts, is in an earlier post which also attracted some helpful comments. I welcome further comments and discussion.