Scientists may have discovered the first observational evidence of string theory, and the new model believes that space-time is quantum, and its inference is in striking agreement with dark energy observations, which is expected to reveal the nature of the accelerating expansion of the universe.

Physicists have proposed a new model of space-time, which may provide "the first observational evidence" for string theory. According to a new preprint study, the model may even solve the mystery of dark energy – the mysterious force that drives the universe to expand at an accelerated pace.

The researchers' calculations reveal that space-time exhibits profound quantum properties at tiny scales, which are very different from the smooth, continuous world we experience every day. Their findings point out that the coordinates of space-time are "not exchangeable", meaning that the order in which they appear in mathematical equations directly affects the results of calculations. This property is similar to the way particles are described in quantum mechanics.

And one of the most astonishing corollaries of this quantum space-time, predicted by string theory, is that it naturally leads to the accelerated expansion of the universe. Even more excitingly, the team found that the rate at which the accelerated expansion predicted by the model slowed down over time matched the latest observations from the Dark Energy Spectroscopy Instrument (DESI).

Michael Kavic, a professor at the State University of New York at Alderwestbury, a co-author of the study, explained to Live Science via email: "If we look at it through the lens of our research, then DESI's observations may be regarded as the first observational evidence in support of string theory, and may even be the first observable concrete effect of string theory and quantum gravity theory." ”

Back in 1998, the mystery of the expansion of the universe ushered in a turning point. At that time, two separate research teams, the Supernova Cosmology Project and the High-Redshift Supernova Search Team, discovered an astonishing fact: instead of slowing down as previously thought, the expansion of the universe is accelerating! They relied on observations of distant supernovae that were dying stars that were much brighter than expected. This discovery strongly hinted at an unknown mysterious force that pervaded the universe, which was later named "dark energy".

However, where exactly the dark energy comes from remains an open question. A popular hypothesis speculates that it may arise from quantum fluctuations in a vacuum, as is the case with phenomena observed in electromagnetic fields. However, when physicists tried to calculate the expansion rate of the universe based on this idea, the results were jaw-dropping: the theoretical calculations were a full 120 orders of magnitude larger than the observations! This huge gap is undoubtedly a serious challenge to the existing theories.

Recent observations from DESI have added new complexity to this mystery. According to the Standard Model of particle physics, if dark energy is only a manifestation of vacuum energy, then its density should remain constant throughout the history of the universe. But DESI's data tell a different story: the accelerating expansion rate of the universe is not static, but slowing down over time. This is precisely what the Standard Model cannot explain.

In order to overcome these theoretical dilemmas, researchers have turned to string theory, one of the most promising candidates to unify gravity and quantum mechanics. Unlike the Standard Model, which treats elementary particles as "points" without volume, string theory paints a more subtle picture: the basic units that make up everything are not points, but extremely small, constantly vibrating one-dimensional "strings." The different vibrational modes of these strings correspond to the different particles we observe, including the imaginary particle that transmits gravitational interactions, the graviton.

In a new and yet peer-reviewed paper published in the preprint database arXiv, physicists Sunhaeng Hur, Djordje Minic, and Tatsu Takeuchi from Virginia Tech, Vishnu Jejjala from Witwatersrand University, and Michael Kavic aforementioned above, have used string theory to provide an in-depth analysis of space-time at the quantum level.

They used the framework of string theory to replace the Standard Model description of elementary particles, and found that space-time itself is intrinsically quantum and non-reciprocal at the most fundamental level. It is this fundamental breakthrough in the concept of classical physics that allows them to no longer rely solely on experimental data to fit the properties of dark energy, but to derive directly from a basic physical theory.

Surprisingly, their model not only calculates a dark energy density value that is in good agreement with the current observations, but also more accurately predicts that this energy density will gradually decrease over time – which coincides with DESI's latest observations.

Perhaps the most thought-provoking aspect of this study is that it reveals that the value of dark energy depends on two physical quantities at the same time: one is the Planck length, which represents the fundamental scale of quantum gravity, as small as about 10⁻³³ cm; The other is the scale of the vast universe itself, spanning billions of light-years. It is extremely rare in physics to associate such extreme microscopic with extreme macroscopic scales, strongly suggesting that dark energy may be deeply rooted in the quantum properties of space-time itself.

"This suggests that there may be a deeper connection between quantum gravity and the dynamics of the universe than we previously thought would be constant," Michael Kavic noted. Perhaps we have always had a fundamental misconception that the fundamental properties of the universe are static, but this may not be the case. ”

Of course, although the team's explanation of the accelerating expansion of the universe is a major theoretical breakthrough, the correctness of its model still needs to be conclusively confirmed by independent experimental testing. Thankfully, the researchers have come up with some specific protocols to test their ideas. Djordje Minic, a physicist at Virginia Tech and co-author of the paper, explained by email that one of the key verification pathways "involves probing a complex quantum interference pattern." This phenomenon is not possible under the standard framework of quantum physics, but according to the theory of quantum gravity, it should exist. ”

Interference means that when waves (such as light waves or matter waves) are superimposed, they reinforce or cancel each other out, resulting in a unique pattern. In traditional quantum mechanics, interference follows clear rules. However, some quantum gravity models predict more complex interactions that produce "higher-order interference" effects that go beyond standard models. If such effects can be captured in the laboratory, it will undoubtedly be a revolutionary test of the theory of quantum gravity. Minic adds, "These are experiments that can be done on the bench in the near future, let's say three to four years. ”

Of course, the research team did not stop at theoretical construction and waited for the final verdict of the experimental results. They are continuing to deepen their understanding of quantum space-time and actively explore other avenues that may test their theories.

Once confirmed, these discoveries will not only be a landmark breakthrough in solving the mystery of dark energy, but will also provide historic first solid observational evidence for string theory, one of the ultimate theories in fundamental physics that has been pursued for decades.

This article was translated from Live Science and edited by BALI.