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Recently, a team of international physicists has determined a subtle characteristic in cosmic microwave polarization background radiation that will eventually allow them to construct the huge structure of the universe, which measure the masses of neutrons and possibly unveil some mysteries of the dark matter and energy.

POLARBEAR consortium, a paper published in the Astrophysical Journal this week, led by UC Berkeley physicist Adrian Lee, explains the first successful isolation of a “B-mode” produced by gravitational lensing in the polarization of the cosmic microwave background radiation.

Certainly, polarization is the point of reference of radiation’s electric field that can be twisted into a “B-mode” pattern as the light passes through the gravitational fields of massive objects, such as clusters of galaxies.

Adrian Lee, the principal investigator of the study and UC Berkeley professor of physics and faculty scientist at Lawrence Berkeley National Laboratory (LBNL) stated that, “We made the first revelation that you can isolate a pure gravitational lensing B-mode on the sky. Moreover, we have shown you can measure the basic signal that will enable very sensitive searches for neutrino mass and the evolution of dark energy.”

The POLARBEAR team consists of around 70 researchers from around the globe who used the microwave detectors mounted on the Huan Tran Telescope in Chile’s Atacama Desert. The team submitted their study to the journal one week before the shocking 17th March announcement by the competitor group, the BICEP2 (Background Imaging of Cosmic Extragalactic Polarization) experiment that it had discovered the holy grail of microwave background research. That team reported finding the signature of cosmic inflation, a rapidly ballooning of the universe when it was a fraction of a fraction of a second old in the polarization pattern of the microwave background radiation.

Later observations like those that were announced by the Planck satellite last month, have since thrown cold water on the BICEP2 results, suggesting that they did not detect what they claimed to detect. Whereas POLARBEAR may eventually confirm or disprove the BICEP2 results, so far it has focused on interpreting the polarization pattern of the microwave background to map the distribution of matter back in time to the universe’s inflationary period, 380,000 years after the Big Bang.

When it comes to the POLARBEAR approach, it’s different from the one used by BICEP2. It might enable the group to measure when dark energy, the mysterious force accelerating the expansion of the universe, began to dominate and overwhelm gravity, which throughout most of cosmic history slowed the expansion.

Early Universe: A High-Energy Lab

Certainly, the POLARBEAR and BICEP2 both were designed to determine the B-mode polarization pattern, which is the angle of polarization at each point in an area of sky. However, the BICEP2 is based at the South Pole, can only measure variation over large angular scales, which is where theorists predicted they would find the signature of gravitational waves created during the early life of the universe. Gravitational waves could only have been created by a brief and very rapid expansion, or inflation, of the universe 10-36 seconds after the Big Bang “when the early universe was a high-energy laboratory, a lot hotter and denser than now, with an energy a trillion times higher than what they are producing at the CERN Collider,” Lee said.

Near Geneva, there is a huge Hadron Collider, which is trying to create that early era by banging together beams of protons to create a hot, dense soup from which researchers hope new particles will emerge, such as the newly discovered Higgs boson. But observing the early universe, as the POLARBEAR group does may also yield evidence that new physics and new particles exist at ultra-high energies.



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