Researchers led by the University of Warwick have developed the first unified method to identify “space-time fluctuations” – small, random disturbances in the structure of space that appear in many attempts to link quantum physics with gravity.
These minute changes were first proposed by physicist John Wheeler and are expected to appear in many leading theories of quantum gravity. However, different theories predict different types of variability, which has made it difficult for experimental scientists to know exactly which signals to look for.
Converting Concepts into Quantitative Expressions
New research, published in Nature Communicationaddresses this problem by dividing space-time fluctuations into three main groups based on how they behave across space and time. In each phase, the team identified clear, measurable patterns that can be detected using laser interferometers — from large facilities such as the 4km-long LIGO to smaller experiments such as QUEST and GQUEST being developed in the UK (Cardiff University) and the USA (Caltech) respectively.
Dr. Sharmila Balamurugan, Associate Professor, University of Warwick and first author said: “Different models of gravity predict fundamentally different patterns of random periodic fluctuations, and have left experimenters without a clear objective.
“It means that we can now test a whole class of quantum-gravity predictions using existing interferometers, rather than waiting for an entirely new technology. This is an important step in bringing some of the most fundamental questions of physics firmly into the experimental realm.”
What the Study Has Revealed
The findings highlight several key points about how different devices can detect these changes:
- Tabletop interferometers beat LIGO in bandwidth.
Although they are very small, systems like QUEST and GQuEST can provide detailed information about the changing atmosphere over time. Their broad spectrum allows them to capture all modes of important signals. - LIGO is a good “yes/no” tool.
Because of its long arm gaps, LIGO is very sensitive to changes in spacetime. However, the frequencies involved fall outside the range currently available in public data. - A long-standing dispute is settled.
This study addresses the ongoing question of whether arm gaps improve cognition. The results show that they enhance sensitivity, depending on the type of variable studied.
Dr. Sander Vermeulen, Caltech, co-author of the study said: “Interferometers can measure spacetime with extraordinary precision. However, to measure the change in spacetime with an interferometer, we need to know what – that is, what frequency – it looks like, and what the signal will look like. The tools to search for quantum gravity.”
A Changing Tool for Basic Physics
An important strength of this framework is that it does not rely on any single explanation of how this change occurs. Instead, it only requires a mathematical description of the proposed changes and details about making the measurements. Its versatility makes it useful not only for studying gravity, but also for investigating gravitational waves, possible dark signals, and certain types of experimental noise.
Professor Animesh Datta, Professor of Theoretical Physics at Warwick concluded: “With this method, we can now treat any proposed type of space-time variability in a uniform, comparable way. In the coming years, we can use this to design smart interferometers to verify or disprove potential quantum theories or new grafting theories and theories in testographical graft and semiclassic gratis waves.”
This work was funded by the UK STFC “Quantum Technologies for Basic Physics” program (Grant numbers ST/T006404/1, ST/W006308/1 and ST/Y004493/1) and the Leverhulme Trust under research grants ECF-2024-121 and RPG-0202.
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