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A hint of new physics in the polarized radiation from the early universe



A hint of new physics in the polarized radiation from the early universe

As the light of the cosmic microwave background emitted 13.8 billion years ago (left image) moves through the universe as it is observed on Earth (right image), the direction in which the electromagnetic wave oscillates (orange line) rotates at an angle β . The rotation can be caused by dark matter or dark energy interacting with the light of the cosmic microwave background, which changes the patterns of polarization (black lines inside the images). The red and blue areas of the images show hot and cold areas of the space microwave background, respectively. Credit: J. Minami / KEK

Using Planck data from cosmic microwave background radiation, an international team of researchers observed a hint of new physics. The team developed a new method for measuring the polarization angle of ancient light by calibrating it with dust emissions from our own Milky Way. Although the signal is not detected with sufficient accuracy to draw definite conclusions, it may suggest that dark matter or dark energy causes a violation of the so-called “parity symmetry”.


It is believed that the laws of physics that govern the universe do not change when turned in a mirror. For example, electromagnetism works the same way, whether you are in the original system or in a mirror system in which all spatial coordinates are inverted. If this symmetry, called “parity”, is broken, it may contain the key to understanding the elusive nature of dark matter and dark energy, which account for 25 and 70 percent of the universe’s energy budget, respectively. While both are dark, these two components have opposite effects on the evolution of the universe: dark matter attracts, while dark energy causes the universe to expand faster and faster.

A new study involving researchers from the Institute for Particle and Nuclear Energy Research (IPNS) at the High Energy Accelerator Research Organization (KEK), the Kavli Institute for Physics and Mathematics of Kavli Kavli (Kavli IPMU) of the University of Tokyo and the Max Astrophysics Institute Planck (MPA) reports an annoying hint of new physics – with a confidence level of 99.2%, which breaks the symmetry of parity. Their findings are published in the journal Physical examination letters on 23 November 2020; the paper was selected as a “Editor’s Suggestion,” rated by the magazine’s editors as important, interesting, and well-written.

The hint of breaking the symmetry of parity was found in the cosmic microwave background radiation, the residual light from the Big Bang. The key is the polarized light of the cosmic microwave background. Light is a propagating electromagnetic wave. When it consists of waves oscillating in a preferred direction, physicists call it “polarized.” Polarization occurs when light is scattered. Sunlight, for example, consists of waves with all possible directions of oscillation; thus it is not polarized. Meanwhile, the light of the rainbow is polarized because sunlight is scattered by water droplets in the atmosphere. Similarly, the light of the cosmic microwave background is initially polarized when it is scattered by electrons 400,000 years after the Big Bang. Because this light travels through the universe for 13.8 billion years, the interaction of the cosmic microwave background with dark matter or dark energy can cause the β-plane of polarization to rotate (Figure).

“If dark matter or dark energy interacts with the light of the cosmic microwave background in a way that breaks the symmetry of parity, we can find its signature in the polarization data,” said Utah Minami, a postdoctoral fellow at IPNS, KEK.

To measure the angle of rotation β, scientists need polarization-sensitive detectors, such as those aboard the Planck satellite of the European Space Agency (ESA). And they needed to know how polarization-sensitive detectors were oriented toward the sky. If this information was not known with sufficient accuracy, the measured polarization plane appeared to be rotated artificially, creating a false signal. In the past, the uncertainty regarding the artificial rotation introduced by the detectors themselves limited the accuracy of measuring the cosmic polarization angle β.

“We have developed a new method for determining artificial rotation using polarized light emitted by dust in our Milky Way,” Minami said. “With this method, we have achieved an accuracy that is twice that of the previous work, and we can finally measure β.” The distance traveled by light dust in the Milky Way is much shorter than that of space. microwave background. This means that the emission of dust is not affected by dark matter or dark energy, ie. β is present only in the light of the cosmic microwave background, while artificial rotation affects both. Thus, the difference in the measured polarization angle between the two light sources can be used to measure β.

The research team applied the new method to measure β from polarization data taken from the Planck satellite. They found a hint of breaking the symmetry of parity with a confidence level of 99.2%. In order to claim the discovery of a new physics, a much greater statistical significance or confidence level of 99.99995 percent is needed. Eiichiro Komatsu, director of the MPA and chief researcher at Kavli’s IPMU, said: “It is clear that we have not yet found conclusive evidence for new physics; higher statistical significance is needed to confirm this signal. But we are excited, because our new method has finally allowed us to make this “impossible” measurement, which may point to a new physics. “

To confirm this signal, the new method can be applied to any of the existing – and future – experiments measuring the polarization of the space microwave background, such as Simons Array and LiteBIRD, which involve both KEK and Kavli IPMU.


The cosmic confusion of the microwave background


More info:
Utah Minami et al. New extraction of cosmic birefringence from Planck 2018 polarization data, Physical examination letters (2020). DOI: 10.1103 / PhysRevLett.125.221301

Provided by Kavli Foundation

Quote: A Hint of New Physics in Polarized Radiation from the Early Universe (2020, November 25), retrieved on November 27, 2020 from https://phys.org/news/2020-11-hint-physics-polarized-early- universe.html

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