A few nice articles on a career in science. I'll add some words of my own later.
- On Becoming a Scientist by Bruce Alberts
- A wake-up call by Bruce Alberts
- Audacious Science Series by Science Career Staff
Science News: Physicists Successfully Store and Retrieve Nothing
It sounds like a headline from the spoof newspaper The Onion, but for physicists, this is actually an achievement: Two teams have stored nothing in a puff of gas and then retrieved it a split second later.
I am attending a workshop at KITP on Sr2RuO4 starting this Monday, Dec 10th. I will be posting some news and development for my personal reference. It also has a wiki page.
Nature has a collection of articles on the "many-worlds" quntum theory 50 years after it was first expounded by Hugh Everett III for his PhD thesis. The articles have a running theme of science fiction as well. I have yet to read all of them, but the News Feature (subscription) and the Commentary articles are both nicely written.
It is said sometimes that physicists constantly simplify the problems they are trying to solve by considering simple models. This is true but not the whole story, or even the important part of it. Simple models must also be relevant, otherwise they are worthless. This is usually expressed by saying that the said simple model contains the important/relevant physics one is trying to address. This, I think, is far more crucial to what physicists do than the simplicity of their models which is a reflection of our modest abilities. It is a reflection of our immodest abilities in finding the correct solution.
The reason I am writing this is that today I saw Richard Muller's lecture webcast of Tue 11/7/2006, which started, due to the occasion, by his icecream model of elections. It is a simple model that argues there is no or little difference between the candidates in a two-party system. However, it does so by assuming a whole load of assumptions that are not explored in Muller's short discussion. For instance, it assumes there is a continuous, static, and spacially coordinated one-dimensional spectrum of political opinions. It also assumes that the candidates can move more or less continuously over this political spectrum without losing any votes on the opposite side of their oppponent. In short, it is a simple model, but one that does not contain the right physics.
Nature reports (subscription) that the Princeton Engineering Anomalies Research (PEAR) lab is finally closed down by its founder, Robert G. Jahn, the former Dean of the School of Engineering and Applied Science. In the 28 years that it operated it pursued, their web site says,
rigorous scientific study of the interaction of human consciousness with sensitive physical devices, systems, and processes common to contemporary engineering practice.Nature puts what the lab did more clearly as investigating "whether people can alter the behaviour of machines using their thoughts." But Nature seems to be a little confused about the real questions involved in this event. It says that "the closure highlights a long-running question: how permissive should science be of research that doesn't fit a standard theoretical framework, if the methods used are scientific?"
Is that really the question? The confusion comes from the bit about "scientific method". The same label enters the lab's self-description, augmented by the adjective "rigorous". However, these labels all ignore that the scientific method is basically an extension of the good old method of "trial and error", or as Popper insisted, "trial and elimination of error".
What the lab did, and other similar enterprises do, is only half the story, namely, the trial part. What's seriously missing is the part of elimination of error. The lab did not ask "the wrong questions" as Nature's headline claims (what does that mean anyway?): it refused to accept that the answers they were giving were false by the evidence collected by themselves and others. They refused to accept the almost trivial fact that whatever they found or didn't find were explained categorically better by competing theories.
Islamic "quasicrystals" predate Penrose tiles
Quasicrystals are patterns that fill all the space but lack translational symmetry. Such a structure will produce diffraction patterns when illuminated with light, but without the usual crystalline symmetries. It now seems that the findings of the University of Copenhagen crystallographer Emil Makovicky about the occurance of quasicrystalline patterns in Iran's Islamic architectural decorations and tilings are not just accidental. New findings by Peter J. Lu of Harvard University and Paul Steinhardt of Princeton University (Science 315, 1106)
show that by 1200 C.E. a conceptual breakthrough occurred in which girih patterns were reconceived as tessellations of a special set of equilateral polygons ("girih tiles") decorated with lines. These tiles enabled the creation of increasingly complex periodic girih patterns, and by the 15th century, the tessellation approach was combined with self-similar transformations to construct nearly perfect quasi-crystalline Penrose patterns, five centuries before their discovery in the West.
D-Wave Systems has announced a quantum computing demo that they say would be a first in computing history: an end-to-end 16-qubit quantum computer. The date of the demo in Vancouver is February 15, 2007.
Entanglement and statistical mechanics
In two recent papers by two independent groups (in Nature Physics and in Physical Review Letters), 80 years after quantum mechanics was first put together in a coherent fashion, it is shown that the assumption of equal probability in statistical mechanics can be justified within quantum physics. Basically, these groups show that even if the whole universe (system+environment) is in a pure state in a constrained Hilbert space, if the environment is sufficiently large, the density operator of the system will be sufficiently close to the one obtained by assuming an equal-probability density operator for the Universe in the constrained Hilbert space.
Complex $p$-wave superconductivity
A University of Illinois group headed by D. J. Van Harlingen have found evidence for the theoretically-predicted $p+ip$ superconductivity in the ruthenate compound, Sr2RuO4. They have used phase-sensitive Josephson junction experiments to measure the symmetry of the gap function. Van Harlingen was also part of the group who determined the $d$-wave nature of cuprate superconductors using similar phase-sensitive experiments in 1995. The complex order parameter breaks time-reversal symmetry. This effect has also been recently observed in Kerr-effect (see also the wikipedia article) measurements, which detect the rotaion in the polarization of an incident light on a chiral material. Maurice Rice's perspective is very much worth reading.
A European experimental group reports to have measured the probability of production of vortices in a bagel-cheese-bagel setup of superconducting and insulating rings as a function of the rate of cooling below the critical temperature, in agreement with the Kibble-Zurek predictions (square root of the cooling rate). This is an in-principle test of the cooling theory of the Universe in its first microseconds of life. Also, the measurement is claimed to be "the only condensed matter experiment to date to have measured a scaling exponent with any reliability."
Popper, Bayes and the inverse problem
Albert Tarantola, a geophysicist in Paris, presents a model of solving the "inverse problem" (using the result of measurements to infer the values of the parameters representing a system) which is in accordance to the Popperian view of scientific method. I find the text to be a little divergent at parts (links to evolutionary psychology of humans are at best amusing) but the essence of the argument is worth remembering: "observations cannot produce models, they can only falsify models."
