Astrophysics and Gravitation:
The Milky Way Project aims to sort and measure our galaxy, the Milky Way. Initially we’re asking you to help us find and draw bubbles in beautiful infrared data from the Spitzer Space Telescope.
Understanding the cold, dusty material that we see in these images, helps scientists to learn how stars form and how our galaxy changes and evolves with time.
The GalaxyZoo project expands! Help astronomers out when you’re feeling in the mood to procrastinate.
GREAT10, a simulation challenge that aims to improve image analysis algorithms for cosmic gravitational lensing.
GREAT10 is a way for astronomers, astrophysicists, computer vision, and AI people to come together and find new ways of solving problems. Contest details are online.
For more, see Computer Geeks: Compete to Help NASA Explain Dark Energy.
High Energy Physics and Particles:
2010 Ion Run Complete at CERN
From CERN Bulletin:
After a very fast switchover from protons to lead ions, the LHC has achieved performances that allowed the machine to exceed both peak and integrated luminosity by a factor of three. Thanks to this, experiments have been able to produce high-profile results on ion physics almost immediately, confirming that the LHC was able to keep its promises for ions as well as for protons.
Another milestone finished; it’s been a great year for the LHC.
For more, see CERN Bulletin.
General Relativity, Quantum Gravity, et al.:
GravityGeek for Christmas
GravityGeek is a cooperative project to help encourage interaction amongst physicists in gravitation/general relativity with journalists and the public.
GravityGeek, the beta collaboration/networking site for professionals in general relativity, quantum gravity, cosmology, etc., has recommendations for Christmas/other gift giving, in case you have a physicist to buy for (as well as non-technical recommendations for kids and those who just like good popular science literature).
For more, see The GravityGeek Mission.
Fun with 2D Blackholes
Abhay Ashtekar, Frans Pretorius, & Fethi M. Ramazanoğlu (2010). Surprises in the Evaporation of 2-Dimensional Black Holes arXiv arXiv: 1011.6442v1
Quantum evaporation of Callen-Giddings-Harvey-Strominger (CGHS) black holes is analyzed in the mean field approximation. The resulting semi-classical theory incorporates back reaction. Detailed analytical and numerical calculations show that, while some of the assumptions underlying the standard evaporation paradigm are borne out, several are not. Furthermore, if the black hole is initially macroscopic, the evaporation process exhibits remarkable universal properties. Although the literature on CGHS black holes is quite rich, these features had escaped previous analyses, in part because of lack of required numerical precision, and in part because certain properties and symmetries of the model were not recognized. Finally, our results provide support for the full quantum scenario recently developed by Ashtekar, Taveras and Varadarajan.
This is fairly nice for something so dense to read (it’s a lot crammed into four pages). The key result: for 2D black holes, information in the matter profile on Ī⁻R will not all be recovered at Ī⁺R, in generality. Slight twists on our understanding of 2D black holes might be suggestive of solutions in 4D. Of course, the usual problems of discussing anything in 2D are still there, but still…
Cyclic Circles in the Sky? Probably Not
The big topic of the past few weeks has been Roger Penrose and V.G. Gurzadyan’s November paper, suggesting there was evidence, via circle matching in the CMB, of a cyclic cosmology. There are so many papers being discussed right now, that this requires it’s own section. Now, because Penrose being a co-author makes any paper big news, mainstream media was all over this “evidence for time before time” (and other completely offensive and nonsensical catchphrases). What Gurzadyan and Penrose believed they had shown was that patterns in the CMB could not fit with standard inflationary cosmology and were strongly suggestive of a cyclic cosmology – ie. multiple “big bangs” (so our big bang wasn’t the first/didn’t start the cosmic clock, so to speak). Now, many people who’ve looked for circles in the CMB (because it could be very suggestive of the topology/geometry/history of the universe) were sceptical of this, because, unfortunately, patterns in the CMB are a little like bible codes. If you’re just looking for something, with a data set that big, you’re bound to find it and it doesn’t make it at all meaningful. Doubters appeared quickly on the arXiv and in blogs, and Gurzadyan and Penrose quickly responded in kind (see NASA, this is how it’s supposed to work). Below are the papers in the discussion as it stands, from November 16th to today:
The Original Paper
V. G. Gurzadyan, & R. Penrose (2010). Concentric circles in WMAP data may provide evidence of violent pre-Big-Bang activity arXiv arXiv: 1011.3706v1
Critique #1 by Wehus & Eriksen
I. K. Wehus, & H. K. Eriksen (2010). A search for concentric circles in the 7-year WMAP temperature sky maps arXiv arXiv: 1012.1268v1
Critique #2 by Moss, Scott & Ziblin
Adam Moss, Douglas Scott, & James P. Zibin (2010). No evidence for anomalously low variance circles on the sky arXiv arXiv: 1012.1305v1
The response from Penrose and Gurzadyan
V. G. Gurzadyan, & R. Penrose (2010). More on the low variance circles in CMB sky arXiv arXiv: 1012.1486v1
Critique #3 by Hajian
Amir Hajian (2010). Are There Echoes From The Pre-Big Bang Universe? A Search for Low Variance Circles in the CMB Sky arXiv arXiv: 1012.1656v1
Basically, the critiques (1 & 2) go as follows: Yes, the patterns you’re seeing are really there, but they don’t mean what you think they mean. They’re just random, it’s not significant. Response: No, you don’t understand, they are significant, we have proof here. They can’t be random, it’s not a Gaussian distribution. Critique 3: No, I just checked, my Monte Carlo simulations showed they were random, sorry.
Honestly, it’s hard to believe, based on what has been shown, that these patterns are anything meaningful, but the discussion is certainly not over, and I’m sure that there will be many more papers being written on this, well into the new year.
For more, see Nature News: No evidence of time before Big Bang.