localitybound

Localitybound is a theoretical concept in high-energy physics and quantum gravity that describes a bound on the achievable locality or spacetime resolution of physical processes. It arises from thought experiments that combine quantum mechanics with general relativity, indicating that concentrating enough energy into a sufficiently small region to probe smaller distances inevitably produces strong gravitational backreaction, potentially forming a black hole. In such scenarios, the notion of a strictly local measurement or interaction breaks down, implying a limit to how finely events can be localized.

The locality bound is often formulated as a relation between the localization scale and the energy or momentum involved, suggesting there exists a minimum practical localization length beyond which local quantum field theory ceases to be predictive. This leads to the idea that locality is not fundamental at all scales but an emergent or approximate feature at lower energies or larger distances. The bound is frequently discussed in discussions of quantum gravity, the Planck scale, and nonperturbative effects where gravitational effects cannot be neglected.

Implications of locality bounds include a motivation for nonlocal or holographic descriptions of physics at extreme energies, and they are cited in debates about the UV completion of quantum field theory and the nature of spacetime. Critics point out that effective field theories can remain useful within their domains of validity, and that a precise, universally agreed-upon mathematical formulation of a locality bound remains an area of active research. See also Planck scale, holographic principle, nonlocality, and gravitational backreaction.