An axis of evil in the sky: a sign of the need of new physics?

By on March 16, 2014
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The average temperature in our universe is very consistent, varying by only a few millionths of a degree in any direction. This even temperature pattern, known as the cosmic microwave background (CMB), is one of the strongest pieces of evidence that our universe began with the big bang, is continuously expanding, and homogenous.

However, slight asymmetries in the temperature pattern suggest a lopsided orientation of our universe and give rise to the “axis of evil,” a region of marked temperature anisotropy around a temperature axis that dwarves event the biggest of galaxies. The order of this temperature pattern hints at what could be a different look at the physics that were at play in the early universe expansion.

Amanda Yoho, a graduate student in cosmology at Case Western Reserve University is interested in this anomaly.

“I think the alignment, in conjunction with all of the other large angle anomalies, must point to something we don’t know, whether that be new fundamental physics, unknown astrophysical or cosmological sources, or something else,” Yoho said.

The temperature of the universe is measured by examining the CMB. The CMB is a uniform background of microwave radiation that permeates the universe, and it can be nicely explained by the big bang. In the time period right after the big bang, matter was so dense and hot that atoms could not form, and a soup of subatomic particles opaque to radiation filled the universe.

As space expanded, the mixture cooled until it reached a critical temperature at which atoms could form. This event, known as recombination, left behind a world transparent to radiation, and its warmth became background radiation.

Over the past billions of years, the expansion of the universe redshifted this radiation from the infrared into microwaves, leaving the CMB. Random fluctuations in temperatures allowed density irregularities to form in this matter soup, paving the way for the formation of celestial objects. These, however, are small fluctuations that could be explained by the accepted model. The size of the axis of evil, however, makes it unlikely to be the result of random fluctuations, possibly necessitating a revision to the current model for the universe.

The term “axis of evil” was given to this ordered energy by astronomers Kate Land and Joao Magueijo as a riff off a statement given by former president George W. Bush. Theories on how the axis of evil came about vary, but one of the probable mechanisms is inflation.

The early universe saw a rapid expansion after the big bang that decreased sharply in rate. Multiple variations of the exact mechanisms of inflation are all capable of explaining this axis.

Marc Kamionkowski, a cosmologist at Johns Hopkins University maintains that this is only a preliminary idea of the axis of evil, if it even exists at all.

“These CMB anomalies, if real, will pose similarly big questions for fundamental physics and for the prevailing inflationary paradigm…” Kamionkowski said. “The case that these anomalies are real is, however, nowhere nearly as well established.”

However, the current dataset is not conclusive enough to test any of the theories and the supposed axis may still actually be nonexistent. On the other hand, it may well indicate the need of a new physics. No matter what it may be, though, further studies will need additional evidence and data to support any conclusion.

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