Does the “Mirror World of Particles” Explain the Crisis in Cosmology?

The idea of ​​a mirror universe is a common trope in science fiction. A world like ours where we can find our evil doppelganger or a version of us who really asked our high school crush out. But the concept of a mirror universe has often been studied in theoretical cosmology, and as a new study shows, it could help us solve problems with the cosmological constant.

The Hubble constant, or Hubble parameter, is a measure of the rate at which our universe expands. This expansion was first demonstrated by Edwin Hubble using data from Henrietta Levitt, Vesto Slipper and others. Over the next several decades, this expansion was measured at a rate of about 70 km/s/Mpc. Give or take a little Astronomers thought that as our measurements became more accurate, various methods would settle on a similar value, but that didn’t happen. In fact, over the years the measurements have become so accurate that they completely disagree. it is sometimes referred to as problem of cosmic tension,

The values ​​observed in the two clusters of the Hubble stable cluster at this point. Measurements of fluctuations in the cosmic microwave background point to a low value, about 67 km/s/Mpc, while observations of distant supernova-like objects yield a higher value of about 73 km/s/Mpc. Something clearly doesn’t add up, and theoretical physicists are trying to figure out why. This is where the mirror universe can come in.

The mirror of our world in the stars. credit: Beat Bachchan via Pixabay

The popularity of wild ideas declines in theoretical physics. The mirror universe idea is no exception. It was studied quite early in the 1990s as a way to tackle the problem of matter-antimatter symmetry. We can create particles of matter in the laboratory, but when we do, we also create particles of antimatter. They always come in pairs. So when particles formed in the early universe, where did all their antimatter siblings go? One view was that the universe itself formed as a pair. Our matter universe and a similar antimatter universe. problem solved. The idea fell out of favor for a variety of reasons, but this new study looks at how it could solve the Hubble problem.

The team discovered an invention called the . is referred to as unitless parameter, The most famous of these is the fine structure constant, which has a value of about 1/137. Basically, you can add up the measured parameters in such a way that all units cancel out, giving you the same number no matter what units you use, which is great if you’re a theorist. The team found that when you change the cosmological model to match the observed expansion rate, many of the unitless parameters remain the same, suggesting an underlying cosmic symmetry. If you apply this symmetry more broadly, you can measure the rate of gravitational free-fall and the rate of photon-electron scattering so that the different methods of Hubble measurement agree better. And if this immutability is real, it means that a mirror universe exists. One that would affect our universe through a weak gravitational pull.

It should be noted that this study is mostly a proof of concept. It explains how this cosmic invention can solve the Hubble constant problem, but doesn’t go so far as to prove that it is a solution. This would require a more detailed model. But it is an interesting idea. And it’s good to know that if your evil doppelganger is out there, they can only gravitationally affect your life…

Reference: Sire-Racine, Francis-Yan, Fei Ge, and Lloyd Knox. ,The Symmetry of Cosmic Observables, a Mirror World Dark Sector, and the Hubble Constant, physical review paper 128.20 (2022): 201301.

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