Dr. Nguyen Nhat Minh – Photo: NVCC
As time passes and the universe evolves, scientists expect that large structures in the universe – that is, networks of matter connecting galaxies – will grow at a certain rate predicted by a relatively comprehensive theory by scientist Albert Einstein.
Populations and clusters of galaxies, such as concentrated regions of matter, are becoming increasingly dense, while regions of space are becoming increasingly empty.
Understand More About Gravity and Dark Energy
Researchers at the University of Michigan have also shown that when dark energy (a type of energy of unknown nature but common in the universe) accelerates the expansion of the universe, the gap between theory and data becomes more and more apparent.
The main author of the work is Nguyen Nhat Minh – a young Vietnamese cosmology researcher, alumnus of the Department of Theoretical Physics, Ho Chi Minh City University of Natural Sciences. The discovery was published in Physical Review Letters, which is top-ranked by Google Scholar in mathematics and physics. Due to the importance of the discovery, this research was considered an outstanding work by the editorial office of the American Physical Society and was reported by several international physics journals.
Galaxies everywhere in the universe are strung together like a giant spider’s web. Their distribution in space is not random but clustered together. In fact, the entire web of matter in the universe began as small clumps of matter in the early universe, gradually evolved into individual galaxies, and eventually became clusters and filaments of galaxies.
The universe is not made only of matter. Most likely it also involves a mysterious component called dark energy. Dark energy accelerates the expansion of the entire universe. Since dark energy accelerates the expansion of the universe, it has the opposite effect on larger structures.
Dr. Nhat Minh analyzed: “If gravity acts like an amplifier that amplifies physical perturbations, promoting them to grow into larger structures, then dark energy acts like an attenuator that causes them to grow larger.” “The disturbance weakens and hinders the development of these structures”. Therefore, according to him, “By understanding how structures in the universe assembled and evolved, we can understand more about the nature of gravity and dark energy.”
Matter in the early universe gradually combined into larger cosmic structures in the late period – Illustration: NHAT MINH – MAI THANH
We were surprised by the high statistical strength of this evidence of abnormal growth suppression. Honestly, I feel like the universe is trying to tell us something. It is now up to us cosmologists to interpret these findings.
GS Dragon Hutterer
Continue studying the motion of galaxies
Dr. Nhat Minh and his colleagues, Prof. Dragon Hutterer and Dr. Youwei Wen (both from the University of Michigan) have researched the temporal evolution of large structures during the evolution of the universe using multiple space exploration data sources.
According to Michigan News, they were the first to use the cosmic microwave background (or CMB), which consists of photons emitted shortly after the Big Bang that created the universe. These photons provide a snapshot of the early universe. When photons reach our telescopes, their path can be bent due to gravity from larger structures along the way. By studying this phenomenon, researchers can estimate the composition and distribution of matter in the universe.
Cosmologists have taken advantage of the phenomenon in which “the light of distant background galaxies is distorted by the gravitational interaction with matter between them and telescopes”, by decoding the distortions they have been able to determine whether the matter How it is distributed between us and distant background galaxies.
“Importantly, the cosmic microwave background and background galaxies are at different distances from our telescopes, so the weak gravitational lensing of galaxies gives us information about the distribution of matter in the universe at a time closer to us than before. Inferred from the weak gravitational lens of the cosmic microwave background,” Nhat Minh explained to The Michigan News.
Cosmologists continue to study the motion of galaxies in the nearby universe, to track the evolution of structure even at later times. When galaxies come under the gravitational influence of cosmic structures, their movements provide information directly related to the evolution of that structure.
New research results explain the “S8 paradox”?
The researchers’ new discovery has the potential to resolve the so-called “S8 paradox” in cosmology. S8 is a parameter that describes the evolution of cosmic structure. The disagreement arose when scientists used two different methods to determine the value of S8 and the values obtained from the two methods did not agree with each other.
The first method, using photons from the cosmic microwave background, shows higher S8 values than those predicted from measurements of weak gravitational lensing (which stretches and bends the observed shape of stars) and the clustering of galaxies.
Both the above methods do not measure the evolution of the structure at the present time. Instead, they study the structure of earlier times, then extrapolate to the present time, assuming the Standard Model is the correct model of the universe. The structure obtained from the cosmic microwave background is closer to the early universe, while the structure obtained from gravitational lensing and galaxy clustering is to the later universe, closer to the present day.
According to Dr. Nhat Minh, the researchers’ findings on the evolutionary suppression of matter and structure in the late universe would make the two S8 values from the above two measurements completely consistent together.
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