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Strict Limit On CPT Violation From Gamma-Ray Bursts

December 11, 2012 Leave a comment

Kenji Toma (Osaka Univ.), Shinji Mukohyama (Kavli IPMU, Univ. of Tokyo), Daisuke Yonetoku (Kanazawa Univ.) and their colleagues have used the photon polarization in three distant gamma-ray bursts detected by Japanese spacecraft as evidence that the polarization did not rotate during its long journey. This lack of rotation puts the most stringent constraints yet on the violation of a fundamental symmetry. This work is going to be published and highlighted in Physical Review Letters.

Photons produced by gamma-ray bursts (GRBs) that occur in the universe travel billions of light-years to reach us. This makes them excellent probes of space-time structures on extremely small scales that are being actively studied in quantum gravity theories.

Some quantum gravity theories, trying to unify Einstein’s theory of relativity with quantum mechanics, (e.g., superstring theory) predict that structures of space-time at extremely short distances may be totally different from what we think we know. If this symmetry is broken at extremely short distances, as predicted in some quantum gravity theories, polarization of photons from distant celestial objects would rotate during its long journey to us. However, several attempts to detect this rotation have come up empty, implying that nature obeys CPT at least to a level of one part in 10 million.

In this work, Toma and his colleagues have improved on these limits using data from the Japanese IKAROS spacecraft. “We have confirmed that the CPT symmetry is not violated even at extremely small distances,” Toma comments about the importance of this work. “This result puts a fundamental constraint on quantum gravity, a dream theory reconciling Einstein’s theory of relativity and quantum theory.”

Full Story: http://www.ipmu.jp/node/1458

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Little Telescope Spies Gigantic Galaxy Clusters

December 11, 2012 Leave a comment

Distant galaxy cluster found by WISE. Image credit: NASA/JPL-Caltech/UCLA/WIYN/Subaru

Distant galaxy cluster found by WISE. Image credit: NASA/JPL-Caltech/UCLA/WIYN/Subaru

Our solar system, with its colorful collection of planets, asteroids and comets, is a fleck in the grander cosmos. Hundreds of billions of solar systems are thought to reside in our Milky Way galaxy, which is itself just a drop in a sea of galaxies.

The rarest and largest of galaxy groupings, called galaxy clusters, can be the hardest to find. That’s where NASA’s Wide-field Infrared Survey Explorer (WISE) can help. The mission’s all-sky infrared maps have revealed one distant galaxy cluster and are expected to uncover thousands more. These massive structures are collections of up to thousands of galaxies bound together by gravity. They were born out of seeds of matter formed in the very early universe, and grew rapidly by a process called inflation.

“One of the key questions in cosmology is how did the first bumps and wiggles in the distribution of matter in our universe rapidly evolve into the massive structures of galaxies we see today,” said Anthony Gonzalez of University of Florida, Gainesville, who led the research program. The results are published in the Astrophysical Journal. “By uncovering the most massive of galaxy clusters billions of light-years away with WISE, we can test theories of the universe’s early inflation period.”

Full Story: http://www.jpl.nasa.gov/news/news.php?release=2012-388