In line with the usual mannequin of cosmology, that enlargement price must be the identical regardless of the way you measure it. However lately, scientists have discovered that the enlargement price of the early universe and that of the more moderen universe fluctuate by roughly 9 %.
That discrepancy, or pressure, “has provoked heated debates within the cosmology group about whether or not this distinction might be on account of systematic errors or whether or not it’s a sign of recent physics,” Teixeira and her co-authors wrote. Their mannequin posits that in a world the place darkish vitality and darkish matter work together, what gave the impression to be a disaster brought on by disparate enlargement charges as an alternative turns into one thing to be anticipated.
A Darkish Dimension
If darkish vitality and darkish matter do work together, it might imply that they’ve a standard origin, Khoury stated.
Ongoing work in string idea—the concept our universe, at its smallest, most basic stage, is made up of vibrating strings—suggests a means these ideas could be related. In 2019, constructing on the concept in string idea that darkish vitality is of course various, Vafa and two collaborators concluded that the mass of darkish matter particles can also fluctuate over time. This led them to suggest in 2022 that darkish matter and darkish vitality might share a hyperlink with a so-called darkish dimension.
String idea posits the existence of six or seven additional dimensions along with our acquainted three dimensions of area and one among time. All of those dimensions are considered as small as bodily doable—near the Planck scale (10-35 meters)—however the researchers proposed that the darkish dimension might be considerably larger than the others—on the order of a micron (10-6 meters).
Gravitons, theoretical particles that impart the power of gravity, might leak into this enlarged darkish dimension. In the event that they did, they might decide up mass and change into what are referred to as darkish gravitons. These huge gravitons would reside at midnight dimension, however their gravitational results might be felt in different dimensions, permitting them to meet the position that’s usually ascribed to darkish matter.
On this situation, “there’s a very pure coupling between darkish vitality and darkish matter,” stated Georges Obied, a physicist on the College of Chicago. Adjustments within the measurement of the darkish dimension would have an effect on each darkish vitality and darkish matter.
In a July 2025 paper, Obied and Vafa, together with Alek Bedroya of Princeton and David Wu of Harvard, discovered that the situation proposed in 2019 was in step with the DESI information. Their mannequin predicts that the energy of darkish vitality and the mass of darkish matter will lower over time and that the speed at which darkish vitality modifications will probably be proportional to its vitality density. As a result of astrophysical measurements inform us that the vitality density of darkish vitality is very small, “it received’t change quick,” Vafa stated.
“It’s not shocking that we didn’t see it till now,” he stated, as a result of the speed of change is so tiny. “We needed to wait the whole age of the universe to detect one thing that small.”
