Subtle Distortions May Reveal Clues To The Early Universe

Brett Smith for – Your Universe Online

Based on observations from the South Pole Telescope, a team of international scientists has found subtle patterns in the cosmic microwave background called B-mode polarizations, according to a report in Physical Review Letters.

“The detection of B-mode polarization by South Pole Telescope is a major milestone, a technical achievement that indicates exciting physics to come,” said study author John Carlstrom, a deputy director of the Kavli Institute for Cosmological Physics at the University of Chicago.

“The detection of a primordial B-mode polarization signal in the microwave background would amount to finding the first tremors of the Big Bang,” added co-author Duncan Hanson, a postdoctoral scientist at McGill University in Canada.

The cosmic microwave background is composed of the light particles that are remnants of the Big Bang. They fill all of space at a temperature of minus 270 degrees Celsius. Scientists have been mapping small shifts in temperature of the light across the sky by multiple experiments, providing a wealth of information.

Some light from the cosmic microwave background became polarized when photons were scattered off of electrons in the early universe, in much the same way light is polarized as it reflects off the hood of a car. These types of polarization patterns are known as “E modes,” which have been easier to detect than the fainter B-modes.

B-mode polarization patterns are generated by a more complex process. Scientists have long thought that E modes can be twisted into B-modes by gravitational lensing, a phenomenon that occurs when the trajectory of light is bent by massive objects such as galaxies. The new study confirms this theory.

To uncover B modes, the scientists first determined where the gravitational lensing should occur by looking at mass distribution across the universe. Next, they combined data on E modes with the mass distribution to create a model for the creation of B-modes.

Study researchers said researching B-modes would provide evidence of inflation, the theory of a rapidly expanding universe taking place moments after the Big Bang. Inflation is a popular theory because its predictions agree with known data. However, cosmologists have yet to definitively confirm the theory.

B-modes from inflation are thought to be caused by the gravitational waves that would have been generated by intense gravitational turmoil. Measuring B-mode polarization would confirm the theory of inflation and give scientists information about physics at extremely high energies.

Study researchers said finding B-modes from gravitational lensing is a major first step in the pursuit to measure inflationary B modes. When cosmologists are searching for inflationary B-modes, lensing B-modes show up as noise.

“The new result shows that this noise can be accounted for and subtracted off so that scientists can search for and hopefully measure the inflationary B modes underneath,” Hanson said. “The lensing signal itself can also be used by itself to learn about the distribution of mass in the universe.”

Physics World magazine recently named the study’s results one of the top 10 physics breakthroughs of 2013.

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