This Week in the Universe: December 14th – December 20th

This will be an especially short one, as I’m sitting in a hotel room in Idaho right now and didn’t pre-write anything, but check out 10 Delicious Papers from 2010 for more fun!

Astrophysics and Gravitation:

Hints of a Multiverse?

Stephen M. Feeney, Matthew C. Johnson, Daniel J. Mortlock, & Hiranya V. Peiris (2010). First Observational Tests of Eternal Inflation arXiv DOI: 1012.1995


The abstract:

The eternal inflation scenario predicts that our observable universe resides inside a single bubble embedded in a vast multiverse, the majority of which is still undergoing super-accelerated expansion. Many of the theories giving rise to eternal inflation predict that we have causal access to collisions with other bubble universes, opening up the possibility that observational cosmology can probe the dynamics of eternal inflation. We present the first observational search for the effects of bubble collisions, using cosmic microwave background data from the WMAP satellite. Using a modular algorithm that is designed to avoid a posteriori selection effects, we find four features on the CMB sky that are consistent with being bubble collisions. If this evidence is corroborated by upcoming data from the Planck satellite, we will be able to gain insight into the possible existence of the multiverse.

Interesting, but far from conclusive, evidence has been found suggesting the possible existence of the multiverse.  Of course, these observations could also happen if there was no multiverse, but they allow for the possibility of its existence.  Further study will say more one way or the other (although it’s likely to never be conclusive).

For more, see Cosmic Radiation Features Could Suggest Our Universe Is Not Alone.

High Energy Physics and Particles:

No Mini Black Holes at the LHC, No One is Surprised

CMS Collaboration (2010). Search for Microscopic Black Hole Signatures at the Large Hadron Collider arXiv arXiv: 1012.3375v1

So no micoscopic black holes have been produced or detected at the LHC.  This is not surprising; it’s almost not even news.  Outside of the tabloids, I don’t think very many people thought there was any chance of it happening, as very few versions of quantum gravity would allow for black hole production at these, relatively low, energy levels.  However, ruling things out is always important (but it isn’t this grand failure of string theory as some people are claiming).

For more, see Search for microscopic black hole signatures at the Large Hadron Collider, LHC confirms a modest stringy prediction on black holes, Missing Black Holes Cause Trouble for String Theory, String Theory Fails Another Test, the “Supertest”.

General Relativity, Quantum Gravity, et al.:

Something Loopy This Way Comes?

Marcin Domagala, Kristina Giesel, & Wojciech Kaminski, Jerzy Lewandowski (2010). Gravity quantized arXiv DOI: 1009.2445

So I’m honestly not sure why this one is here, but io9 did a write up that seems to have a lot of people talking.  Okay, so I haven’t read more than the abstract (I’m supposed to be on vacation!), but the abstract was fairly lackluster.

Here is the abstract in its entirety:

…”but we do not have quantum gravity.” This phrase is often used when analysis of a physical problem enters the regime in which quantum gravity effects should be taken into account. In fact, there are several models of the gravitational field coupled to (scalar) fields for which the quantization procedure can be completed using loop quantum gravity techniques. The model we present in this paper consist of the gravitational field coupled to a scalar field. The result has similar structure to the loop quantum cosmology models, except for that it involves all the local degrees of freedom because no symmetry reduction has been performed at the classical level.

You guys can tell me if it’s worth reading when I’m back.

For more, see Loop quantum gravity could unite physics and take us back to the Big Bang.

Say Good-Bye to the Pioneer Anomaly

Slava G. Turyshev, & Viktor T. Toth (2010). The Pioneer Anomaly arXiv DOI: 1001.3686

This is actually great (although far too long to read unless you’re especially interested).  I’ll direct you to the wonderful summaries below, but basically, the Pioneer anomaly, an anomaly some people suggest indicates problems with general relativity, is probably not an anomaly at all.

For more, see The Pioneer Anomaly, a 30-Year-Old Cosmic Mystery, May Be Resolved At Last, Farewell, Pioneer Anomaly?.

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