Articles & Reviews
Authored by RSF Research Staff
Discovering properties of elementary particles by studying galactic structure – a unified approach
By: William Brown
The cosmological inflationary paradigm has seen notable support and agreement with observational data in the 30 years since it was first introduced  (Inflationary universe: A possible solution to the horizon and flatness problems, Alan Guth, 1981). There are, however, a number of outstanding questions, several of which pose significant challenges. For instance, how is it that the early universe formed density perturbations, which produced the large scale galactic structures extant today, when it was supposed to be remarkably homogenous. Standard theory explains such density gradients as resulting from quantum vacuum fluctuations occurring in the early universe which would have produced micro-scale inhomogeneities, providing the seed structures to form galaxies and their large-scale cosmological order (these seed structures are most accurately described as primordial black holes).
Another particular challenge comes from the nebulous predictive power of the Standard Model in explaining the structure and order observed today, in that the mass spectrum of fundamental particles will change depending on what parameters are present during different cosmic inflation models (which can have any number of different potential values). Under such potential variability of the Standard Model, there is no way to predict a priori what values will be “settled upon”, it is an utterly random event, and therefore there is no reason to believe that if the Big Bang was to be ran again it would result in anything close to resembling the organization and properties of our current universe.
A team including Xingang Chen of the Harvard-Smithsonian Center for Astrophysics (CfA), Yi Wang from the Hong Kong University of Science and Technology (HKUST)—who worked with Nima Arkani-Hamed and Juan Maldacena—and Zhong-Zhi Xianyu from the Center for Mathematical Sciences and Applications at Harvard, have described a method to explain how properties of the elementary particles were created at the Big Bang by studying the largest structures in the cosmos.
The method is based on the understanding that the initial microscopic structures of the early universe, like elementary particles, become imprinted in the largest-scale structures of the later universe, like galaxies and the cosmic microwave background radiation. Therefore, by studying the statistics, spatial distribution, and other properties of the universe at the largest scale, researchers can gleam keen insights into the nature of the smallest scale objects—fundamental particles.
“The relative number of fundamental particles that have different masses — what we call the mass spectrum — in the Standard Model has a special pattern, which can be viewed as the fingerprint of the Standard Model,” explained Zhong-Zhi Xianyu. “However, this fingerprint changes as the environment changes, and would have looked very different at the time of inflation from how it looks now.”
The team showed what the mass spectrum of the Standard Model would look like for different inflation models. They also showed how this mass spectrum is imprinted in the appearance of the large-scale structure of our universe. This study paves the way for the future discovery of new physics.
Such a technique is not new, physicist Nassim Haramein has applied this method of studying the largest scale distribution of structures and properties of the universe to understand the smallest, and vice versa, with remarkable success. Haramein and astrophysicist Amira Val Baker have applied the quantum gravitational solution to the proton’s mass and radius to explain the exact parameters of inflation in their cosmological model, which provides a first-principles model to predict and explain the fundamental constants and properties of elementary particles that will form following inflation.
There is a unification across scale, where the smallest objects are imprinted in the properties of the largest, and the largest scale structures influence and give rise to properties of the smallest.
“If we are lucky enough to observe these imprints, we would not only be able to study particle physics and fundamental principles in the early universe, but also better understand cosmic inflation itself. In this regard, there are still a whole universe of mysteries to be explored,” said Xianyu.
The research by Xianyu’s team is detailed in a paper published in the journal Physical Review Letters on June 29.
 A. H. Guth, Inflationary universe: A possible solution to the horizon and flatness problems. Phys. Rev. D 23, 347 (1981); A. D. Linde, Phys. Lett. B 108, 389 (1982); A. Albrecht and P. J. Steinhardt, Phys. Rev. Lett. 48, 1220 (1982).
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