This Week in the Universe: December 20th – December 27th

Since I’m in the Rockies soaking up my last few days of vacation, I haven’t actually looked at much this week, but there were two papers I thought were worth noting.

Astrophysics and Gravitation:

Reconstructing Histories with Good Statistics

Tracy Holsclaw, Ujjaini Alam, Bruno Sanso, Herbert Lee, Katrin Heitmann, Salman Habib, & David Higdon (2010). Nonparametric Dark Energy Reconstruction from Supernova Data Phys. Rev. Lett. arXiv: 1011.3079v1

The abstract:

Understanding the origin of the accelerated expansion of the Universe poses one of the greatest challenges in physics today. Lacking a compelling fundamental theory to test, observational efforts are targeted at a better characterization of the underlying cause. If a new form of mass-energy, dark energy, is driving the acceleration, the redshift evolution of the equation of state parameter w(z) will hold essential clues as to its origin. To best exploit data from observations it is necessary to develop a robust and accurate reconstruction approach, with controlled errors, for w(z). We introduce a new, nonparametric method for solving the associated statistical inverse problem based on Gaussian process modeling and Markov chain Monte Carlo sampling. Applying this method to recent supernova measurements, we reconstruct the continuous history of w out to redshift z=1.5.

As the paper says, “In order to extract useful information from cosmological data, a reliable and robust reconstruction method for w(z) [the equation of state parameter] is crucial”, and that’s what this paper aims to provide.  It’s not the most exciting thing you’ll ever read (although it is short), but without work along these lines, much of cosmology and astrophysics is actually pretty meaningless, so it’s certainly worth remembering that.

For more, see Statistical modeling could help us understand cosmic acceleration.

General Relativity, Quantum Gravity, et al.:

Brane Holes

Valeri P. Frolov, & Shinji Mukohyama (2010). Brane Holes arXiv arXiv: 1012.4541v1

The abstract:

The aim of this paper is to demonstrate that in models with large extra dimensions under special conditions one can extract information from the interior of 4D black holes. For this purpose we study an induced geometry on a test brane in the background of a higher dimensional static black string or a black brane. We show that at the intersection surface of the test brane and the bulk black string/brane the induced metric has an event horizon, so that the test brane contains a black hole. We call it a brane hole. … We discuss thermodynamic properties of brane holes and interesting questions which arise when such an extra dimensional channel for the information mining exists.

Who doesn’t love higher dimensional solutions for black holes?  Honestly, I haven’t had time to give this a thorough read yet but it looks rather promising.

For more, see Cosmologists Discover How Black Holes Can Leak.

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