361. NEQNET: first two weeks of April

Well, it seems that other two weeks have passed… What’s up? First of all, it looks like I figured out why energy seems to dissipate inhomogeneously in a turbulent flow with very large Reynolds numbers (kindly see the list N4 below). Apart from this topic, other things that I was interested in during these two weeks are listed here:

1. String theory, field theory, quantum gravity

1.1. What is twistor. Everybody seems to get a bit crazy about twistor formalism in string theory and Y.-M. lately, so I’ve decided it’s time finally for me to learn what is it all about…

1.2. Twistors and non-linear differential equations. Curved spacetime, where I continue discussing twistors. While I explain how using the language of twistors allows to express solutions of linear differential equations (and free massless fields) in the previous post, here I discuss how twistors help dealing with non-linear differential equations.

1.3. Twistors: getting more formal, where I give a formal definition of twistor as a straight line in projective space and discuss symmetries of .

1.4. Thermal equilibrium in special relativity by David Cubero (U. of Sevilla). Consider a single ultrarelativistic (say, massless) particle coupled to a heat bath. The motion of this particle is Brownian, and the magnitude of the random force acting on it is defined by the temperature of the bath. What happens with Langevin and Fokker-Planck equations if we describe the motion of the particle using proper time instead of world time? Post gives an answer to this question.

2. Cosmology

2.1. Cosmological parameters in the context of time varying w by Rahul Biswas (U. of Illinois). How much will our estimations of cosmological parameters change if we allow the effective equation of state to change with time (or with redshift )?

3. Nuclear physics

3.1. Thermonuclear fusion: some basic facts about thermonuclear reactions. Since I’ve included thermonuclear fusion in my list of 10 most important open problems in physics, it would be only fair for me to present “a bit deeper than basic level” review of physics behind it. Here I discuss the very basic of thermonuclear fusion like Coulomb barrier and a couple of strategies that can help us pursue the problem.

3.2. Thermonuclear fusion. Coulomb barrier and reaction rates (and the second part). Continuation of the previous post, devoted to estimation of reaction rates.

3.3. Introduction into thermonuclear reactors. That’s what it is: I classify different reactors according to the scheme of confinement of plasma they use.

4. Hydrodynamics, turbulence

4.1. Vortex line representation. Cauchy invariant. The goal of this post is to demonstrate the nature of infinite number of (non-local) integrals of motion that exist for Eulerian flows. As it turns out, the physics behind them is vorticity field frozen into the motion of the ideal incompressible fluid.

4.2. Vortex line representation. Clebsch variables. In this post, I derive equations of motion for vortex lines frozen into Eulerian flow.

5. Fun and stuff

5.1. Interview with Bogzabraloff brothers: science and religion. Two of the deepest thinkers of our time, Bogzabraloff brothers, explain their views on interplay between science and religion.

5.2. How much should you publish? Really, this question is not as meaningless as it sounds. How much should you publish in order to be considered competitive on the physics job market? Let us figure out together.

5.3. The question of quality. Maybe number of your publications is less important than the quality of your research. But how to measure the quality of your research quantitatively? Is the total number of citations a metrics that is good enough to estimate it? What is h-factor and how good is that metrics?

5.4. Followup: BumpTop. As it turns out, BumpTop finally goes out of the private beta stage – you can download it for free even if you don’t have an invite code.

5.5. Trading olympiad. Interactive Brokers has just announced that the 2009 IB Collegiate Trading Olympiad is now over. The winner gets 200000$ – a nice addition to his fellowship.

5.6. 48 years ago. Space opened its doors for Major Yuri Gagarin on Apr 21 1961. Did it really close its doors for us then?

There is a couple of other rather exiting things I was dealing with during these 14 days but I am not ready to disclose it to you yet… To stay in touch, you can subscribe to NEQNET daily email updates or RSS feed.