Amazing stuff, but way above my head! A new theory from Finland!
"At long last, a unified theory combining gravity with the other fundamental forces—electromagnetism and the strong and weak nuclear forces—is within reach. Bringing gravity into the fold has been the goal of generations of physicists, who have struggled to reconcile the incompatibility of two cornerstones of modern physics: quantum field theory and Einstein’s theory of gravity. ...
The key was finding a way to describe gravity in a suitable gauge theory — a kind of theory in which particles interact with each other through a field. ‘The most familiar gauge field is the electromagnetic field. ..."
From the abstract:
"The Standard Model of particle physics describes electromagnetic, weak, and strong interactions, which are three of the four known fundamental forces of nature.
The unification of the fourth interaction, gravity, with the Standard Model has been challenging due to incompatibilities of the underlying theories—general relativity and quantum field theory.
While quantum field theory utilizes compact, finite-dimensional symmetries associated with the internal degrees of freedom of quantum fields, general relativity is based on noncompact, infinite-dimensional external space-time symmetries.
The present work aims at deriving the gauge theory of gravity using compact, finite-dimensional symmetries in a way that resembles the formulation of the fundamental interactions of the Standard Model.
For our eight-spinor representation of the Lagrangian, we define a quantity, called the space-time dimension field, which enables extracting four-dimensional space-time quantities from the eight-dimensional spinors.
Four U(1) symmetries of the components of the space-time dimension field are used to derive a gauge theory, called unified gravity. The stress-energy-momentum tensor source term of gravity follows directly from these symmetries. The metric tensor enters in unified gravity through geometric conditions. We show how the teleparallel equivalent of general relativity in the Weitzenböck gauge is obtained from unified gravity by a gravity-gauge-field-dependent geometric condition. Unified gravity also enables a gravity-gauge-field-independent geometric condition that leads to an exact description of gravity in the Minkowski metric. This differs from the use of metric in general relativity, where the metric depends on the gravitational field by definition. Based on the Minkowski metric, unified gravity allows us to describe gravity within a single coherent mathematical framework together with the quantum fields of all fundamental interactions of the Standard Model.
We present the Feynman rules for unified gravity and study the renormalizability and radiative corrections of the theory at one-loop order.
The equivalence principle is formulated by requiring that the renormalized values of the inertial and gravitational masses are equal.
In contrast to previous gauge theories of gravity, all infinities that are encountered in the calculations of loop diagrams can be absorbed by the redefinition of the small number of parameters of the theory in the same way as in the gauge theories of the Standard Model. This result and our observation that unified gravity fulfills the Becchi–Rouet–Stora–Tyutin (BRST) symmetry and its coupling constant is dimensionless suggest that unified gravity can provide the basis for a complete, renormalizable theory of quantum gravity."
New theory of gravity brings long-sought Theory of Everything a crucial step closer (original news release) "A quantum theory of gravity would clear the path to answering some of the biggest questions in physics."
Gravity generated by four one-dimensional unitary gauge symmetries and the Standard Model (open access)
Mikko Partanen (left) and Jukka Tulkki, the two authors of this study
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