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.

Happy Birthday Tesla ! Tuesday, Jul 11 2006 


Nikola Tesla

Happy Birthday Tesla !

I guess, I am late by a day. Or probably not, since July 10th is yet to end in U.S.- the country where Tesla spent most of his life. Anyway, it is difficult to add to the already ongoing celebrations of Tesla in the blogsphere. So, I will content myself with providing some links.

Nikola Tesla Wikipedia Page – to get a taste of what Tesla was. Also have a look at PBS page on Tesla . You can view a Google-video on Tesla and his inventions here. Lastly, do check out the post titled “Happy Birthday Nikola Tesla” by Coturnix(scienceblogs.com) – A comprehensive list of links associated with Tesla and His Birthday celebrations.

Yuzik, Are you a theorist ? Saturday, Jul 8 2006 

pomeranchuk.jpg
Isaac Pomeranchuk
© Moscow Engineering Physics Institute (state university), 2002

Via Amar, I came to know of an interesting quote attibuted to a physicist called Pomeranchuk. In the words of L.B.Okun

When I became a student of Pomeranchuk in 1950 I heard from him a
kind of a joke that the Book of Physics has two volumes: v.1. is “Pumps
and Manometers”, v. 2. “Quantum Field Theory”.

As I read this quote, I suddenly realised that I know near to nothing about Pomeranchuk ! So, after some digging around I came across a short biography at ArXiv. According to the author of that biography,

In 1934-35 his [Pomernachuk’s] advisor became Alexander Iosifovich Shalnikov (1905 – 1986).
Many years later academician Shalnikov recalled that he started by bringing
Yuzik to a room full with old vacuum pumps glass-ware and leaving him
there. Two weeks later, entering the room, Shalnikov found that everything
that could be broken was broken. ‘Yuzik, are you a theorist?”, – uttered
Shalnikov. “I don’t know. And what?” – was the answer.

And hence the title of this post . 🙂

As you might expect, apart from the above biography, it is very difficult to find material on Pomeranchuk on the web. So, I would rether list here some miscellaneous links dealing with his work.

Approach to Absolute Zero – 4. Below 10 milli-Kelvin by R Srinivasan , A Resonance article has a section on Pomeranchuk cooling.

If a mixture of liquid and solid
3He is compressed isentropically
below 0.3 K, part of the liquid turns into solid absorbing heat
and the temperature of the liquid falls. This is the principle
of Pomeranchuk cooling.

And to quote the wikipedia article on Pomeron,

In physics, the Pomeron is a force-carrying pseudo-particle postulated in 1961 to explain energy behavior of soft hadronic collisions at high energies. It appeared first in the framework of the phenomenological Regge theory of strong interactions at high energies, but later a similar object was derived from the first principle QCD calculations.

The existence of the pomeron as well as some of its properties have been reasonably well established experimentally, notably at Fermilab. In particular, it is believed that the pomeron carries no net charges. The absence of electric charge implies that pomeron exchange does not lead to the usual shower of Cherenkov radiation, while the absence of color charge implies that such events do not radiate pions.

This is in accord with experimental observation. In high energy proton-antiproton collisions in which it is believed that pomerons have been exchanged, a rapidity gap is often observed. This is a large angular region in which no outgoing particles are detected.

The name honors the Ukrainian physicist Isaak Pomeranchuk for his theoretical work in 1960’s on high-energy scattering.

Some other articles on Pomeron :

And I would be happy to include any other link about Pomeranchuk which might turn up in the comments section.

Supersymmetry series at TowardsTengen Friday, Jul 7 2006 

Background: Nothing more than basic Quantum Mechanics, actually. Knowing a bit of QFT would be useful, but not essential.

I’m trying to write up a bit about what I’ve been doing, the first (badly written) installment is up here.  In case you check it out, let me know if there are any errors or mistakes.
Link: http://towardstengen.wordpress.com/2006/07/07/susy/

Enjoy Physics …

Link Dump Friday, Jul 7 2006 

This post is mainly a collection of a lot of nice links to Physics related resources. Enjoy! :

And the best for the last …

  • John Baez:
  • Baez is a mathematical physicist at the university of California. He writes a weekly column on This Week’s Finds in mathematical Physics. Wonderfully written, and a really nice source of information of all sorts. This may require a little bit of maths, but he writes in a lucid and interesting way that even if you’re in your first year, UG, you will definitely learn something from each article, and the good news is there are archives going back to around 200 weeks!

  • Mark Sredniki:
  • This is a nice QFT book, it’s available online now, soon, it’s going to be taken off after it is published in print, so hurry and get your copy now! [Thanks to Tarun, for pointing this on out]. I’ve seen this once earlier, and it seemed really nice, especially has a nice section on spinors, and dotted & undotted indices, unless I’m confusing it with something else.

“Electroweak Interactions” by Georgi Wednesday, Jul 5 2006 

georgi.jpg
Howard Georgi

Background : Quantum Field theory

Link : Weak Interactions – Howard Georgi

This is an online version of a monograph by Howard Georgi on Weak interactions. Do check out his homepage too . There are other interesting material including a review on effective field theory .

And I don’t know what to make of the B.A. thesis titled Les Phys by P.J.Dong (PDF file) linked from there. It seems like a drama with lots and lots of physics songs 🙂

And also check out another link from his webpage which points to some interesting articles on women in science. It includes the PDF slides and a streaming video of Georgi’s own lecture titled Women and the Future of Physics