Source: MSN
Story by Tejasri Gururaj
A unified theory of everything has long eluded scientists due to gravity being irreconcilable with the three other fundamental forces (electromagnetic, weak, and strong) described using quantum field theory (QFT).
The fundamental discrepancy between the unification lies in how the two theories are described. The gravitational field—described by Einstein’s theory of general relativity—is a manifestation of the very fabric of reality, spacetime.
On the other hand, the Standard Model uses principles of QFT to describe the electromagnetic, weak, and strong fields.
However, the fundamental difference is that these quantum fields are defined on spacetime. This means they exist as fields throughout spacetime, with a value associated with every point in it.
Thus, reconciling the two remains a gruelling challenge for scientists. Aalto University scientists have proposed a fresh perspective on gravity designed to integrate gravitational theory with the Standard Model.
A new approach to gravity
In the framework of the Standard Model, the three fundamental forces arise due to certain symmetries in their quantum fields. Each force has a unique symmetry pattern associated with it.
To develop a similar framework for gravity, the researchers introduce a new mathematical quantity called the spacetime dimension field. This entity has four symmetries that give rise to the gravitational field when applied to every point in spacetime.
Categories: Physics, Quantum physics
“A theory that coherently describes all fundamental forces of nature is often called the Theory of Everything,” Aalto University postdoctoral researcher Mikko Partanen said. It has been the physicists’ holy grail, a thorn in the side of earlier researchers. The thrilling prospect of a union of gravity with the nuclear strong and weak forces and electromagnetism has pushed physicists to expand the reach of Einstein’s general theory of gravity and quantum field theory.
The tension between these two pillars of physics in the twentieth century has been an annoying problem. Quantum field theory is a probability-based theory of interactions among infinitesimally small particles and general relativity is a deterministic theory of large-scale geometry of the universe. Both have each been a success, but the two theories cannot be added. Partanen and co-author Jukka Tulkki have devised this solution with the solution of building a new theory of gravity based on the Standard Model of particle physics. The innovation would give a clearer picture of how the universe came into being, i.e., black holes and the Big Bang.
The key to their solution lies in the key to gauge theory. “The most familiar gauge field is the electromagnetic field. When electrically charged particles interact with each other, they interact through the electromagnetic field, which is the pertinent gauge field,” Tulkki states. Fields intervene between particles here, and gravity as a gauge field such as the electromagnetic field is treated. The problem has been to build a gauge theory of gravity that is compatible with the other three forces. The Standard Model is a gauge theory that explains these forces with some symmetries. Partanen and Tulkki’s paper tries to apply these symmetries to gravity, hoping for a quantum mechanics-general relativity unification.
https://www.msn.com/en-us/news/technology/new-quantum-gravity-theory-offers-hope-for-reconciling-quantum-mechanics-and-general-relativity/ar-AA1EvqOg?cmp_prftch=2&ocid=entnewsntp&pc=U531&cvid=c11d144861cd4093fef77a964ef376b0&ei=12
In previous studies, gravity’s role in quantum theory has remained vague. Space-time translations—key to gravity—are generated by differential operators, unlike the internal symmetries of particle physics. The Coleman–Mandula theorem has long implied that gravity’s symmetries can’t be internal like those in the Standard Model.
However, Partanen and Tulkki classify their new U(1) symmetries of gravity as internal under one accepted interpretation: they act directly on the fields without depending on their variations in space-time. This subtle shift makes the symmetries of gravity compatible with those of the Standard Model.
That compatibility matters. It means the same mathematical machinery that powers modern particle physics can now describe gravity too.
https://www.msn.com/en-us/news/technology/new-unified-gravity-theory-could-finally-bridge-einstein-and-quantum-physics/ss-AA1EpZyr?cmp_prftch=2&ocid=entnewsntp&pc=U531&cvid=b9cecd7d50ec4011af651dd797b5b8fc&ei=10#image=6