NEQNET: Non-equilibrium Phenomena

Cosmology, turbulence, markets, non-equilibrium QFT and much more. No nonsense, just science

Tour of Ares IX

Jim Halsell (former astronaut) takes Miles O’Brien on a tour through the various components of the new NASA Ares IX rocket.

Into dark ages or again about GRB090423

Back in April, I already wrote about GRB090423 – currently the most distant detected object in the Universe. Yesterday, two papers with details of mesurement have appeared in astro-ph (unfortunately, Icannot give you the links – see my comment below).

Let me remind you that currently the redshift of the most distant galaxy we observed is about 6.96, of the most distant quasar – 6.43 (redshift values are defined with very good precision), while the redshift of the most distant gamma ray burst (GRB090423) is about 8.3.

The value of the redshift in the latter case is determined by photometry measurements (photometry is not exactly the most precise method we have at our disposal) and from the Lyman- absorption profile (which is much more precise method than photometry). Taking into account that both methods give the same value of the redshift (with corresponding error bars), we can consider the measurement as robust.

In usual Lambda CDM cosmology without any exotics redshift 8.26 corresponds to the age of the Universe 625 million years, and the very detection of the GRB shows that stars were already being born and dying at that time. It is interesting to note that parameters of GRB090423 are pretty much the same as of GRBs detected at lower redshifts – either the mechanics of GRB does not depend on the star much or there were already stars at that time that don’t differ too much from the ones we have today, at .

Via sergepolar.

Update: I realized after writing this blogpost that their paper, since it is submitted to Nature, is under press embargo, so I will remove the link to the paper. Honestly saying, I am not sure whether press embargo has any meaning in this particular case. First of all, the news was everywhere in press back in the end of April – for example, NewScientist made a video about it which is right now on Youtube and had about 65000 views already alone apart from its clones. Second, every dog in physics blogosphere (including your huble correspondent) has blogged about it.

How to spot a black hole on the Sky

Here is a video from NewScientist featuring simulations by Loeb and his collaborators (we have discussed Loeb’s results several times on NEQNET). The idea is that BH acts as a strong gravitational lense, so if we have a close system “star-BH”, we will see a very specific pattern of light when the companion star crosses the “disk” of BH. Of course, in order for us to spot this pattern, it is better if the line of our sight lights in the orbit plane of the star.

This and that in ArXiv on Monday

Due to unbelievable overload of the last days let me simply list the recent papers in ArXiv that I found the most interesting:

1. Quantum information

T. Tilma el al., “Is entanglement a critical resource for quantum metrology?”

Can we beat the shot-noise limit (and get to the Heisenberg limit) in quantum metrology by playing with entanglement of a quantum state? As it turns out, typically the answer is positive, but depending on what exactly you measure there might exist regimes such that entanglement actually prevents achievement of the Heisenberg limit.

2. Quantum field theory, string theory

J. Ellis et al., “The probable fate of the Standard Model“. If you perform RG analysis of the SM, three scenarios may realize depending on the value of the mass of the Higgs. First of all, if Higgs mass is very large, Higgs self-coupling blows up – and we need some non-perturbative physics (which we are currently not quite aware of) to control it. On the other hand, if Higgs mass is very small, the potential of SM is unstable. Finally, SM may survive up to the Planck scale if the mass of the Higgs boson is not too small or too large. Authors try to figure out which scenario will be most probably realized in reality using info that we currently have about constraints on Higgs mass.

Two nice string-theoretic papers, V. Kumar, W. Taylor, “String universality in six dimensions” and T. Erler, M. Schnabl “A Simple Analytic Solution for Tachyon Condensation” are well discussed in the recent Lubos Motl’s post and I don’t have anything to add to what he has said already.

3. Astrophysics and cosmology

W. Buchmueller et al., “Probing Gravitino Dark Matter with PAMELA and Fermi“. The main conclusion of the paper is that fluxes observed by PAMELA and Fermi LAT require astrophysical sources for gravitino dark matter.

QuAD collaboration. “Improved measurements of the temperature and polarization of the CMB from QuAD“. A white paper by QuAD collaboration. QuAD and ACBAR will allow to improve constraints on several cosmological parameters (such as running index) compared to WMAP alone.

D.L. Band et al., “Prospects for GRB Science with the Fermi Large Area Telescope“. Another white paper, for Fermi this time. Large Area Telescope will allow for detection of gamma ray bursts in the > 100 MeV band (the most data we had so far are for 10 keV – 1 MeV band).

EPIC collaboration. Study of the Experimental Probe of Inflationary Cosmology (EPIC)-Intemediate Mission for NASA’s Einstein Inflation Probe. This Monday is definitely the day for white papers – this one is huge, more than 150 pages. Actually, it is a EPIC mission concept report for NASA. EPIC will allow precision measurements of CMB B-modes of polarization.

Bruce Bassett et al., “Fisher Matrix Preloaded – Fisher4Cast“. Authors havedeveloped a very nice software package for working with Fisher matrices.

4. Condensed matter physics

M. Kastner, “Monte Carlo methods in statistical physics: Mathematical foundations and strategies“. Very nice pedagogical introduction into Monte Carlo.

Three last Susskind’s lectures on general relativity

… that is, lectures 10, 11 and 12: gravity in 4+1 dimensions, dynamics of scalars in curved spacetimes (and behavior of gravitational potential – which is scalar), a bit of topology (Euler characteristics), Lagrangian of a relativistic massive point particle, geodesics in curved spacetime and, finally, Schwarzschild solution.

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