유령처럼 보이지 않는 “거울 세계”는 허블 상수와 우주론 논쟁의 원인이 될 수 있습니다

새로운 연구에 따르면 중력을 통해서만 우리 세계와 상호 작용하는 입자의 보이지 않는 “거울 세계”가 오늘날 우주론의 위대한 미스터리를 푸는 열쇠가 될 수 있습니다. 허블 상수 문제.

그만큼 허블 상수 현재 우주의 팽창 속도입니다. 우주론의 표준 모델에서 나온 이 비율의 예측은 다음과 같습니다. 눈에 띄게 느려짐 지역 측정 결과가 가장 정확한 것으로 나타났습니다. 이거 엄청나 네 불일치 불일치 불일치 그녀는 많은 우주론자 중 한 명입니다. 그것을 해결하려고 현재의 우주론적 모델을 변경함으로써. 문제는 표준 모델 예측과 우주 마이크로파 배경과 같은 다른 많은 우주 현상 간의 일치를 손상시키지 않으면서 이를 수행하는 것입니다. 그러한 우주 시나리오가 존재하는지 여부를 결정하는 것은 VJ 뉴멕시코 대학교 물리학 및 천문학과 부교수인 Francis Jan Sir Racine과 캘리포니아 대학교 Davis의 Lloyd Knox를 포함한 연구원들이 연구해온 문제입니다. 대답하기 위해.

나에게[{” attribute=””>NASA, cosmology is the scientific study of the large-scale properties of the universe as a whole. Cosmologists study concepts such as dark matter, and dark energy and whether there is one universe or many, sometimes called a multiverse. Cosmology entails the entire universe from birth to death with mysteries and intrigue at every turn.

Now, Cyr-Racine, Ge, and Knox have discovered a previously unnoticed mathematical property of cosmological models which could, in principle, allow for a faster expansion rate while hardly changing the most precisely tested other predictions of the standard cosmological model. They found that a uniform scaling of the gravitational free-fall rates and photon-electron scattering rate leaves most dimensionless cosmological observables nearly invariant.

“Basically, we point out that a lot of the observations we do in cosmology have an inherent symmetry under rescaling the universe as a whole. This might provide a way to understand why there appears to be a discrepancy between different measurements of the Universe’s expansion rate.”

The research, titled “Symmetry of Cosmological Observables, a Mirror World Dark Sector, and the Hubble Constant,” was published recently in the journal Physical Review Letters.

The COBE satellite was developed by NASA’s Goddard Space Flight Center to measure the diffuse infrared and microwave radiation from the early universe to the limits set by our astrophysical environment. Credit: NASA

This result opens a new approach to reconciling cosmic microwave background and large-scale structure observations with high values of the Hubble constant H0: Find a cosmological model in which the scaling transformation can be realized without violating any measurements of quantities not protected by the symmetry. This work has opened a new path toward resolving what has proved to be a challenging problem. Further model building might bring consistency with the two constraints not yet satisfied: the inferred primordial abundances of deuterium and helium.

If the universe is somehow exploiting this symmetry researchers are led to an extremely interesting conclusion: that there exists a mirror universe very similar to ours but invisible to us except through gravitational impact on our world. Such “mirror world” dark sector would allow for an effective scaling of the gravitational free-fall rates while respecting the precisely measured mean photon density today.

“In practice, this scaling symmetry could only be realized by including a mirror world in the model — a parallel universe with new particles that are all copies of known particles,” said Cyr-Racine. “The mirror world idea first arose in the 1990s but has not previously been recognized as a potential solution to the Hubble constant problem.

“This might seem crazy at face value, but such mirror worlds have a large physics literature in a completely different context since they can help solve important problem in particle physics,” explains Cyr-Racine. “Our work allows us to link, for the first time, this large literature to an important problem in cosmology.”

An artist’s rendition of the COBE Satellite. Credit: Matthew Verdolivo, UC, Davis

In addition to searching for missing ingredients in our current cosmological model, researchers are also wondering whether this Hubble constant discrepancy could be caused in part by measurement errors. While it remains a possibility, it is important to note that the discrepancy has become more and more significant as higher quality data have been included in the analyses, suggesting that the data might not be at fault.

“It went from two and a half Sigma, to three, and three and a half to four Sigma. By now, we are pretty much at the five-Sigma level,” said Cyr-Racine. “That’s the key number which makes this a real problem because you have two measurements of the same thing, which if you have a consistent picture of the universe should just be completely consistent with each other, but they differ by a very statistically significant amount.”

“That’s the premise here and we’ve been thinking about what could be causing that and why are these measurements discrepant? So that’s a big problem for cosmology. We just don’t seem to understand what the universe is doing today.”

Reference: “Symmetry of Cosmological Observables, a Mirror World Dark Sector, and the Hubble Constant” by Francis-Yan Cyr-Racine, Fei Ge and Lloyd Knox, 18 May 2022, Physical Review Letters.
DOI: 10.1103/PhysRevLett.128.201301