Another of Einstein’s theories of gravity may hold the key to alleviating the ‘Hubble problem’

Recent research has explored teleparallel gravity and its ability to resolve the tension surrounding the expansion of the universe in a way that general relativity cannot.

Early in the 20th century, our understanding of the universe was turned on its head when observations by Edwin Hubble revealed that the very fabric of space was expanding.

At the end of the same century, this realization was made more difficult when, by observing the stars as they were leaving the earth, two different teams of scientists discovered that not only is the universe expanding, but the rate of this expansion is increasing.

The reason for this acceleration is a mystery and has been given the placeholder name “dark energy”; The best current explanation for it is the cosmological constant which accounts for a type of background energy called vacuum energy.

The rate of expansion of the universe is known as the Hubble constant, which describes the ratio between the distance of a galaxy from Earth and the speed at which it recedes.

This has been a headache for physicists because the two main methods of determining the Hubble constant are in serious disagreement. This issue is called “Hubble gravity,” and one way to explain it would be by extending our current best model of gravity, general relativity, established by Einstein in 1915.

A paper published in a journal The Physics of the Dark Universe and Celia Escamilla Rivera, a cosmologist at the Institute of Nuclear Sciences, National Autonomous University of Mexico, and fellow researchers, are trying to tackle dark energy and illuminate Hubble’s tension.

“We found that by using gravity models extended beyond general relativity and new cosmic data [observations of distant quasars] we can deal with the Hubble tension and the matter of dark energy on local scales,” Rivera says.

“Using numerical and computational methods, we performed an analysis using different models proposed in ‘teleparallel gravity’ tested for two different cosmological samples that measured distances in the inner universe.”

Teleparallel gravity is an alternative theory to general relativity, which was also invented by Einstein. This “alternative theory of gravity” uses a different set of equations to describe gravity without the curvature of spacetime, and also seeks to link it to one of the other fundamental forces of the universe, electromagnetism.

“Recently, teleparallel gravity has been gaining popularity due to the promise that it can solve the cosmic problem related to the Hubble tension and can explain the nature of the acceleration of the late universe without using the cosmological constant,” Rivera says.

Rivera and his colleagues tested the parameters of this alternative theory of gravity using two new databases of distant and very redshifted quasars, bright regions at the heart of galaxies that are powered by supermassive black holes, observed in ultraviolet, X-ray, and light. visible.

“We are interested in the subject because teleparallel gravity is a suitable candidate for an alternative proposal to general relativity that solves different cosmic problems, as well as having interesting theoretical properties,” Rivera concludes.

“For a wide audience, it is interesting as we test alternative proposals for general relativity to better understand the universe, and for experts in the field, it is a high-level update on specific models in teleparallel gravity. , also using new samples of quasars in transition big top.”