Quantum Physics and Gravitation Linked Through Geodesic Approach

A recent study from Technische Universität Wien, published in Physical Review D, has proposed a novel geodesic approach that links quantum physics with gravitation, moving closer to unifying these two fundamental domains of physics.

Benjamin Koch, a researcher at the Institute for Theoretical Physics, and his team, including Ph.D. student Ali Riahinia and collaborator Angel Rincon from the Czech Republic, explored how geodesics—the shortest paths in curved spacetime—could be redefined in a quantum context.

Traditional geodesics, as defined by Einstein's general relativity, describe the motion of objects in a gravitational field, such as the Earth orbiting the sun due to the sun's mass curving spacetime. However, in this new approach, the team has proposed a quantized version of the metric, leading to what they term the q-desic equation.

This equation shows that, in a quantum spacetime, particles may not always follow the shortest path as classical physics would suggest. Koch noted that when they included the cosmological constant—often associated with dark energy—the differences between q-desics and classical geodesics became significant, particularly on cosmological scales.

While the deviations at smaller distances are negligible, at scales around 10 to the power of 21 meters, the q-desic predictions diverge substantially from classical expectations. The implications of this work open new avenues for testing these theories against observational data, particularly concerning unresolved issues in astrophysics, such as the rotation speeds of spiral galaxies.

Koch expressed hope that their findings could lead to observable predictions that would help distinguish between various approaches to quantum gravity, likening their search for a measurable criterion to finding the right slipper for Cinderella.

This research represents an important step toward the long-sought unification of quantum physics and general relativity, a goal that many physicists consider the 'Holy Grail' of modern physics. The study lays the groundwork for future investigations into how quantum mechanics can alter our understanding of gravitational phenomena on both small and large scales, potentially reshaping our understanding of the universe itself.