Kyushu University’s Institute for Advanced Study and collaborating institutions have provided new evidence suggesting that fundamental constants in quantum gravity may not be arbitrary values imposed from outside the universe, but rather emerge from within the theory itself. The international team led by Associate Professor Yuya Kusuki at Kyushu University investigated conformal field theory (CFT) to determine if a conformal manifold implies the presence of exactly marginal operators. Their work directly addresses a century-old claim by Albert Einstein, who argued that the fundamental equations of physics should not include freely adjustable parameters. “A key challenge in modern physics is understanding whether the laws of nature contain freely adjustable numbers from outside the theory or whether such quantities arise from the theory itself,” explains Kusuki; the team’s findings, soon to be published in Physical Review Letters on June 16, utilize the AdS/CFT correspondence to explore this question.
CFTs and Exactly Marginal Operators Define Conformal Manifolds
The very notion of fundamental constants in physics may require re-evaluation as new research suggests these values aren’t externally imposed, but emerge from the underlying theory itself. A team led by Yuya Kusuki of Kyushu University’s Institute for Advanced Study has demonstrated a link between conformal field theory (CFT) and the potential absence of freely adjustable parameters in quantum gravity, echoing Albert Einstein’s long-held belief that physical laws should dictate their own values. The investigation centers on CFTs, which create a “smooth family of related theories” known as a conformal manifold. Researchers questioned whether a conformal manifold implies the presence of these operators, effectively challenging the idea that parameters are simply set from outside the system.
Utilizing the anti-de Sitter (AdS)/CFT correspondence, a theoretical bridge between CFTs and quantum gravity, the team, including Shota Komatsu from CERN, Dr. Marco Meineri from the University of Turin, and Hirosi Ooguri from the California Institute of Technology, explored this connection under specific assumptions. “By studying how this interface responds when it is displaced slightly, we constructed an operator that generates changes in the parameter. In this way, we identified the origin of what had appeared to be a freely adjustable quantity,” Kusuki stated, describing how the team reconstructed exactly marginal operators from the displacement operator of a conformal interface. These findings support the prediction that quantum gravity may indeed operate without external parameters, offering a pathway toward a deeper understanding of the universe’s fundamental laws.
A key challenge in modern physics is understanding whether the laws of nature contain freely adjustable numbers from outside the theory or whether such quantities arise from the theory itself.
AdS/CFT Correspondence Links Gravity to Interface Operators
The search for a consistent theory of quantum gravity has increasingly focused on the subtle interplay between geometry and quantum information, with researchers now leveraging the AdS/CFT correspondence to probe the origins of fundamental parameters within these theories. This approach builds on the long-held belief, articulated by Albert Einstein a century ago, that the laws of physics should not rely on arbitrary constants imposed from outside the system, but instead emerge from the theory’s internal dynamics. The researchers focused on conformal interfaces, mathematical boundaries separating two related CFTs, and their response to displacement. This reconstruction of an exactly marginal operator from the interface’s displacement operator suggests that continuous parameters aren’t externally “dialed in,” but are instead inherent to the theory itself. “Through the AdS/CFT correspondence, these results support the prediction that ‘there are no freely chosen external parameters’ in quantum gravity,” Kusuki states, adding that future research aims to extend the concept to more general cases of CFT.
Through the AdS/CFT correspondence, these results support the prediction that ‘there are no freely chosen external parameters’ in quantum gravity and are expected to lead to a better understanding of fundamental problems in quantum gravity,” explains Kusuki.
Reconstructing Parameters from Displacement Operators in Two Dimensions
Kyushu University’s Associate Professor Yuya Kusuki and an international team have demonstrated a potential link between internal theoretical operators and what appear to be freely adjustable parameters in quantum gravity, bolstering a claim made by Albert Einstein nearly a century ago. The research, slated for publication in Physical Review Letters on June 16, centers on conformal field theory (CFT) and the AdS/CFT correspondence, a tool allowing physicists to map properties of CFTs to those of quantum gravity in anti-de Sitter space. This approach allows exploration of whether parameters are truly “dialed in” from outside the theory or emerge from its internal structure. Their work hinges on the assumption that a “smooth family of related theories” exists for any two closely related CFTs, connected by an interface that simplifies when the theories converge. Under these conditions, the researchers successfully reconstructed exactly marginal operators directly from the interface’s displacement operator. Currently, the findings apply to CFTs, and the team plans to extend the investigation to more complex scenarios in the future.
Our work shows that continuous changes in a theory can be generated by local operators within the theory,” explains Kusuki.
