From Physics Blogsphere Sunday, Jul 30 2006 

onsager.jpg
Lars Onsager

Over the last few days, I’ve come across a lot of great posts at physics blogsphere.

Blogphysica has already linked to CV once . And I do it again – this time it is a post on N-Body problem by Sean .To quote

… I can’t help but show these lovely exact solutions to the gravitational N-body problem. This one is beautiful in its simplicity: twenty-one point masses moving around in a figure-8.The N-body problem is one of the most famous, and easily stated, problems in mathematical physics: find exact solutions to point masses moving under their mutual Newtonian gravitational forces (i.e. the inverse-square law)…

Check it out – it has some beautiful animations to go along with it. 🙂

Update(03/08/06) : See also the post titled Boltzmann’s Anthropic Brain by Sean and the one by Mark titled A Nonperturbative Analogy at CV.

On another note, Three-Toed Sloth has a good post titled The Nobel Prize Winner as Neglected Genius on Onsager. It is triggered by an RMP article Reviews of Modern Physics 78 (2006): 87–135; free copy (courtesy : TTS ) which is a good but heavy read for those interested in this kind of stuff.

This is the abstract of the article.

Onsager and the theory of hydrodynamic turbulence

Gregory L. Eyink
Department of Applied Mathematics and Statistics, The Johns Hopkins University, Baltimore, Maryland 21218, USA

Katepalli R. Sreenivasan
International Center for Theoretical Physics, Trieste, Italy and Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA

(Published 17 January 2006)
Abstract: Lars Onsager, a giant of twentieth-century science and the 1968 Nobel Laureate in Chemistry, made deep contributions to several areas of physics and chemistry. Perhaps less well known is his ground-breaking work and lifelong interest in the subject of hydrodynamic turbulence. He wrote two papers on the subject in the 1940s, one of them just a short abstract. Unbeknownst to Onsager, one of his major results was derived a few years earlier by A. N. Kolmogorov, but Onsager’s work contains many gems and shows characteristic originality and deep understanding. His only full-length article on the subject in 1949 introduced two novel ideas — negative-temperature equilibria for two-dimensional ideal fluids and an energy-dissipation anomaly for singular Euler solutions — that stimulated much later work. However, a study of Onsager’s letters to his peers around that time, as well as his private papers of that period and the early 1970s, shows that he had much more to say about the problem than he published. Remarkably, his private notes of the 1940s contain the essential elements of at least four major results that appeared decades later in the literature: (1) a mean-field Poisson-Boltzmann equation and other thermodynamic relations for point vortices; (2) a relation similar to Kolmogorov’s 4/5 law connecting singularities and dissipation; (3) the modern physical picture of spatial intermittency of velocity increments, explaining anomalous scaling of the spectrum; and (4) a spectral turbulence closure quite similar to the modern eddy-damped quasinormal Markovian equations. This paper is a summary of Onsager’s published and unpublished contributions to hydrodynamic turbulence and an account of their place in the field as the subject has evolved through the years. A discussion is also given of the historical context of the work, especially of Onsager’s interactions with his contemporaries who were acknowledged experts in the subject at the time. Finally, a brief speculation is offered as to why Onsager may have chosen not to publish several of his significant results.

Of course, you can find this and much more at Mixed states – which is a collection of feeds from lots and lots of physics blogs as explained here . Of course, it right away goes into our blogroll.

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Anderson’s article Saturday, May 6 2006 

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Background: I guess quantum mechanics would do. Since, as usual, high-energy physics is dominating the posts here, it’s time for some condensed matter stuff. Let us start with what is arguably the most famous article in CMP.

Link : P. W. Anderson, “More is different”, Science 177, 393 (1972)
(via the blog http://nanoscale.blogspot.com/ which is one of the very few blogs dealing with condensed matter physics.)

This article outlines what I call the “Anderson philosophy behind CMP” 🙂 In case you didn’t know, P.W.Anderson(Physics Nobel Laureate(1977) – is arguably among the most famous physicists in condensed matter physics. You can find his website at Princeton here and here.

And people who are into condensed matter physics would find this link to Journal Club for Condensed Matter Physics from Bell-labs interesting ….

Posted by : Loganayagam.R.

Life on the Lattice Monday, Apr 17 2006 

Background: This is a blog by two Physicists working on Lattice QCD, and although I can't exactly descibe a clear set of prerequisites, it is technical – a little background in QFT and related stuff is kind of required, I guess, though there's no harm in perusing through it and reading what you like or understand.

Link: Life on the Lattice

One good thing about this blog is that it prides itself on being a Physics blog and not a Physicist's blog

Posted by: Shanth

PS: Tom/Ravi do you guys know of a way that we can enable wordpress to automatically display the login name from which the post was made? If we get that done, then the three of us who have seperate wordpress logins can just post articles and the posted by thing will become automatic, and even the others can probably get accounts soon?