December 7, 2012
Researchers Find Limit On CPT Violation From Gamma-Ray Bursts
Lee Rannals for redOrbit.com — Your Universe Onlinegamma-ray bursts travel billions of light years to reach the Earth. This makes them excellent probes of space-time structures on extremely small scales.
Some quantum gravity theories predict that structures of space-time at extremely short distances may be totally different from what we know. On the scales treated by terrestrial experiments, the world looks exactly the same as its mirror image if the roles of particles and anti-particles are exchanging and the direction of time is reversed.
If this symmetry is broken at short distances, polarization of photons from distance celestial objects would rotate during its journey.
Scientists have made several attempts to detect this rotation, and have come up empty handed. This implies that nature obeys CPT at least to a level of one part in 10 million.
Using data from the Japanese IKAROS spacecraft, scientists detected linear polarization in the gamma-ray emission of three GRBs at the most precise levels so far.
The team used the photon polarization of the three gamma-ray bursts as evidence that the polarization did not rotate during its long journey. This lack of rotation leads to the most stringent constraint on CPT violation, making an improvement of 8 orders of magnitude over previous limits.
“We have confirmed that the CPT symmetry is not violated even at extremely small distances,” Kenji Toma, an author on the paper, said in a statement. “This result puts a fundamental constraint on quantum gravity, a dream theory reconciling Einstein´s theory of relativity and quantum theory.”
IKAROS first launched in 2010, and has been demonstrating photon propulsion and guidance, navigation and control using solar sail successfully during its interplanetary cruise.