Astronomers widely acknowledge that the cosmos is expanding, although the cause of this event remains elusive. In a new paper, researchers suggest that this ever-accelerating expansion could be driven by a mysterious form of matter which does not follow the Standard Model of particle physics.
Cosmic Expansion and Dark Matter
One of the most famous theories on the expansion of the universe is the presence of a mysterious entity called dark energy in the form of a cosmological constant. This leads to expansion at a rate that is independent of the age of the cosmos as well as the temperature of matter and radiation.
However, this hypothesis has been challenged by recent astronomical observations. This prompted scientists to look for alternative ways of explaining the nature of dark energy.
Discrepancies arise in the values of the cosmic expansion rate and the growth of galaxies and galactic clusters between measurements. Observations like the Cosmic Microwave Background measurement contribute to this tension by dimming supernovae and other structures.
Quantities like the Hubble constant determine the rate the expansion of the universe and the so-called S8. These contain information about the formation of large-scale structures, but they are not directly measured. Instead, they are calculated from observations of the cosmic microwave background and distant stars and galaxies using mathematical theories. However, different theories result in different values of the parameters from the same data, posing a huge tension in cosmology.
Exploring the Unparticle Theory
In a recent study, researchers explored the idea that dark energy is instead composed of a theoretical form of matter called unparticles. They believe that this theory aligns better with observations than the prevailing standard cosmological model which assumes a cosmological constant.
The concept of unparticles was introduced more than a decade ago by theoretical physicist Howard Georgi. They are the result of a set of fields with excitations that do not have a well-defined momentum and mass. At the macroscopic level, the unparticles behave as a fluid.
In the study entitled "Emergent Unparticles Dark Energy can restore cosmological concordance", Ido Ben-Dayan of Ariel University combined the unparticle hypothesis with observational data gathered from various experiments. His team discovered that the values of the Hubble constant and the S8 parameter collected from these experiments were consistent with each other when the unparticle theory was used. This is in contrast to the values calculated using the standard cosmological model.
The model also reduced the discrepancy between the measurements of the Hubble constant and S8, restoring the agreement between the various measurements. Although there is no empirical evidence yet to back up this theory, the researchers are confident that the accuracy of astronomical measurements will improve and will help experts determine whether the unparticle theory is correct.
The research team aims to increase the accuracy of their calculations and search for possible manifestations of unparticles in more familiar studies with elementary particles in accelerators. Moreover, they also plan to consider interactions between unparticles and the Standard Model of elementary particles, studying further the extensions of their model and their cosmological consequences.
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