Now, researchers at Aalto University have proposed a new quantum theory of gravity that aligns with the Standard Model of particle physics. The advance could lead to deeper insights into the origins of the universe. While these findings are theoretical, history has shown that similar work often drives practical innovation-for instance, GPS technology relies on Einstein's theory of gravity.

In their recent publication in Reports on Progress in Physics, Mikko Partanen and Jukka Tulkki describe a framework that could eventually yield a comprehensive quantum field theory of gravity. "If this turns out to lead to a complete quantum field theory of gravity, then eventually it will give answers to the very difficult problems of understanding singularities in black holes and the Big Bang," said lead author Partanen.

Partanen noted that such a complete theory is sometimes called the Theory of Everything, although he prefers to avoid the term. "Some fundamental questions of physics still remain unanswered. For example, the present theories do not yet explain why there is more matter than antimatter in the observable universe," he added.

The duo's approach centers on formulating gravity as a gauge theory-a theoretical structure in which particles interact through fields, like the electromagnetic field for electrically charged particles. "So when we have particles which have energy, the interactions they have just because they have energy would happen through the gravitational field," explained Tulkki.

Creating a gravity gauge theory compatible with those describing the electromagnetic, weak, and strong nuclear forces required aligning with the symmetries found in the Standard Model. "The main idea is to have a gravity gauge theory with a symmetry that is similar to the Standard Model symmetries, instead of basing the theory on the very different kind of spacetime symmetry of general relativity," said Partanen.

Without this compatibility, general relativity and quantum mechanics remain fundamentally at odds. Gravity, which is exceedingly weak compared to other forces, has made it especially difficult to observe quantum effects. Yet understanding these effects is essential in extreme environments such as black holes and the early universe.

Inspired by big-picture questions in physics, Partanen developed a new symmetry-based theory of gravity, later refined in collaboration with Tulkki. Their model, if confirmed, could spark a transformative era in physics, akin to the revolutionary insights that followed the development of relativity.

While promising, their work remains incomplete. They have employed renormalization-a method for handling problematic infinities in calculations-and shown that it holds at the first order. Still, full proof requires verifying that the approach holds for higher order terms as well.

"If renormalization doesn't work for higher order terms, you'll get infinite results. So it's vital to show that this renormalization continues to work," said Tulkki. Partanen is optimistic that with time, they can overcome this challenge. "I can't say when, but I can say we'll know much more about that in a few years."

In the meantime, they have published their findings to engage the broader scientific community. "Like quantum mechanics and the theory of relativity before it, we hope our theory will open countless avenues for scientists to explore," Partanen said.

Research Report:Gravity generated by four one-dimensional unitary gauge symmetries and the Standard Model

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Aalto University
The Physics of Time and Space