Asymptotic safety is a theoretical idea suggesting that quantum gravity—the attempt to unify general relativity with quantum mechanics—might be made mathematically consistent and predictive at all energy scales by being non-perturbatively renormalizable.
In quantum field theory, renormalizability ensures that a theory remains well-defined and free of infinities when extended to very high energies. Gravity, when treated as a quantum field theory using standard perturbative methods, becomes non-renormalizable, meaning it leads to uncontrollable infinities. This has long been a major obstacle in developing a quantum theory of gravity.
Asymptotic safety proposes a solution: at very high energies (or short distances), the theory could approach a special kind of behavior known as a non-trivial ultraviolet (UV) fixed point. At this point, the values of certain physical parameters stop changing with energy scale, making the theory effectively stable and predictive, even without requiring new particles or forces.
This idea, originally proposed by Steven Weinberg in the 1970s, implies that quantum gravity could be “safe” from divergences, not because it’s renormalizable in the usual sense, but because it settles into a well-behaved high-energy regime governed by this fixed point.
Asymptotic safety is an active area of research in theoretical physics. While not yet proven, it provides a promising path for developing a UV-complete and consistent quantum theory of gravity—possibly even one that includes the Standard Model of particle physics.