The standard theory of cosmology relies on four fundamental components: space and time, matter, dark matter, and dark energy. Dark energy is the least understood component, making up about 68% of the universe’s total energy density. Recent observations from the Dark Energy Spectroscopic Instrument (DESI) suggest that the rate of cosmic expansion may vary over time.
A recent paper on arXiv explores one modified gravity theory known as Horndeski’s theory, which generalizes Einstein’s original theory of general relativity. This new approach uses a metric tensor to describe spacetime and introduces a uniform scalar field. The study examines how Horndeski models fit the DESI data, finding that they provide a better explanation for the observed time-evolution of cosmic expansion than the standard model.
However, not all Horndeski models are viable when considering dark matter. The research reveals that only certain models where the correlation between the scalar field and dark matter’s time evolution hold true. This means some alternative gravity theories may be ruled out.
The findings suggest that Horndeski’s theory is a promising alternative to general relativity, but it remains to be seen how future DESI results will confirm or challenge these results. As the Dark Energy Spectroscopic Instrument continues to provide new data, Einstein’s status as the foundation of modern cosmology may be reevaluated.
Source: https://www.universetoday.com/170040/observations-by-desi-open-the-door-to-modified-gravity-models