Scientists searched for a “new space-time structure” under the South Pole. Here’s what they found

A new study reports that scientists have looked at the structure of spacetime in search of new physics that can be written into the signatures of elusive ‘ghost particles’, with the help of a giant, sprawling observatory nearly a mile below the South Pole.

Although this years-long experiment did not find any new physics imprinted on these spectral particles, known as neutrinos, it still represents an unprecedented glimpse into the shadowy realms of the cosmos that have remained out of sight until now. In particular, the new research sheds light on the quest to describe gravity using quantum mechanics, because this so-called “quantum gravity” is an important key to unlocking some of the universe’s greatest mysteries.

The IceCube Neutrino Observatory, the world’s largest neutrino telescope, has been operating at the South Pole for a decade. The detector is made up of thousands of sensors that reach about 2,500 meters below the Antarctic ice—roughly the length of 28 football fields—where they capture energetic neutrinos that originate in explosive events from the edge of time and the ‘space.

Now the IceCube collaboration, a team that includes more than 400 scientists, has announced the results of a “search for a new space-time structure” that probed regions of the universe that were previously “inaccessible by human technologies, as reported. a study published Monday in Physics of nature.

“IceCube is really special, because it can see neutrinos coming from very far away and at very high energy,” said Teppei Katori, IceCube team member and experimental particle physicist at King’s College London, as well as co-author of the study study, in a call with the motherboard.

“We use these two properties; that neutrinos can travel the longest distance in the universe and at the highest energy,” he continued. “It’s a big guess, but these particles are thought to be very sensitive to anything within spacetime “.

Neutrinos are so light that their masses are almost imperceptible, earning them the nickname “ghost particles.” For this reason, they are able to effortlessly traverse planets, stars and other forms of matter without slowing down or changing direction. This makes neutrinos very difficult to detect with conventional instruments, even though they are so abundant in the universe that about 100 trillion of them pass through your body every second.

Most neutrinos around Earth are fired by the Sun, but there is another class of high-energy “astrophysical neutrinos” that come from pyrotechnic objects called “cosmic accelerators” that are many billions of miles away. light years from Earth. These accelerators could be objects such as blazars, which are galactic centers that eject beams of light and energy, although the exact sources of astrophysical neutrinos are still unknown.

Neutrinos come in three distinct “flavors” that are associated with fundamental particles in the universe called electrons, muons, and taus. Scientists have long suspected that changes in the flavor of astrophysical neutrinos could open a window into regions of spacetime that could defy what’s known as Lorentz symmetry, which is an important basis of the special theory of Albert Einstein’s relativity.

Lorentz symmetry essentially means that the cosmos should look the same to two observers traveling at a constant speed relative to each other. In other words, the universe on large scales is basically isotropic and homogeneous, although it appears more varied on smaller scales, including the planetary perspective we experience as humans on Earth. Researchers are obsessed with detecting violations of this symmetry because they could expose the longed-for missing link between gravity and the Standard Model of particle physics that governs quantum mechanics.

“For the past 100 years, people have been trying to find proof that Lorentz symmetry is not true, and no one can find it,” Katori explained. “This is one of the most traditional studies in modern physics: people challenging this theory of spacetime.”

“If something doesn’t work in Lorentz symmetry or something is beyond Lorentz symmetry, you might have some connection, for the first time, with gravity in the standard model,” he added. “Quantum gravity is something that a lot of people hope is really the next generation or an open door to the next stage.”

Astrophysical neutrinos offer a promising test of Einstein’s theories because they could encounter unexplored regions of spacetime that are affected by quantum gravity. Neutrinos passing through these areas could change flavor in surprising ways that would leave a record of space-time anomalies in their signatures that could be read by scientists who capture them on Earth.

“The neutrinos change flavor even without this space-time effect,” Katori noted. “We’re looking for anomalous changes or unforeseen ways of changing. That’s the focus of this research.”

The IceCube search found no anomalies in the neutrino flavor conversion, leaving the notion of Lorentz symmetry intact for now. While Katori said these results were a bit “disappointing”—after all, who wouldn’t want to find new physics?—it’s still an important finding. IceCube was able to “unambiguously reach the parameter space of physics motivated by quantum gravity,” according to the study. In other words, the results have opened a new path into the theoretical domain of quantum gravity that will have all kinds of applications for scientists in all fields.

“We think these are great results,” Katori said. “We have the highest sensitivity and we’re also the first experiment to reach some region, or ‘phase space,’ the technical word, to really look for it,” referring to Lorentz symmetry violations.

“I’m so relieved it’s finally being published,” he continued. “From data capture and other issues, it’s such a long effort.”

While this initial experiment is coming to a bittersweet end, a new beginning is emerging from beneath the Antarctic ice, as well as from other instruments around the world. The IceCube collaboration plans to revisit its data set using new machine learning techniques that could identify anomalies that were missed in this study. The team also hopes to dramatically expand the size of IceCube in order to obtain an even larger data set that could eventually reveal traces of space-time anomalies that point to quantum gravity.

“In my opinion, there’s still a chance,” Katori said. “This analysis is the first iteration of its kind. We made this an analysis framework and we developed the code, but in a sense, we didn’t do our best because things are still developing.”

“I think there’s an opportunity to improve it,” he noted, “but I can’t guarantee to what extent.”

Meanwhile, the new results show that it is possible to probe spacetime using slippery particles from the distant universe, providing a way to explore a number of other potential models and experiments.

“Although the motivation for this analysis is to look for evidence of quantum gravity, the formalism we used is model-independent, and our results may set limits to several new physical models, including a new long-range force, dark energy neutrino. coupling, neutrino-dark matter scattering, violation of the equivalent principle, etc.,” IceCube’s contribution to the study concluded.