The discrepancy between early-Universe and late-Universe measurements of the Hubble constant, commonly known as the Hubble tension, has emerged as one of the most significant challenges in modern cosmology. Observations of the Cosmic Microwave Background by the Planck mission favor a Hubble constant of approximately 67 km s⁻¹ Mpc⁻¹, while local distance-ladder measurements from the SH0ES collaboration consistently yield values near 73 km s⁻¹ Mpc⁻¹. The persistence of this discrepancy has motivated numerous proposals involving modified gravity, evolving dark energy, early dark energy, and additional particle sectors. However, a universally accepted explanation has not yet been established. In this work, we investigate the origin of the Hubble constant within the framework of Unified Fractal Quantum Field Theory (UFQFT), in which cosmological evolution emerges from the dynamics of coupled primordial energy and charge fields embedded in fractal spacetime. A cosmological model based on dimensional relaxation toward a critical Hausdorff dimension is developed and used to derive the expansion history of the Universe. The resulting formulation provides a direct relationship between the Hubble parameter and the evolution of fractal geometry. Using the UFQFT framework, the global expansion rate of the Universe is derived from large-scale fractal dynamics and is found to be consistent with the Planck determination of the Hubble constant. The theory is then extended to include local dimensional perturbations associated with environmental variations in fractal spacetime. These local corrections naturally increase the effective expansion rate in nearby regions, yielding values consistent with SH0ES observations. Consequently, both Planck and SH0ES measurements emerge as physically meaningful descriptions of different observational scales rather than mutually incompatible determinations of a single universal constant. The analysis suggests that the Hubble tension may arise from scale-dependent geometric effects associated with fractal spacetime rather than from unknown particle species or additional dark-energy components. The model further predicts specific redshift-dependent signatures that can be tested using forthcoming observations from DESI, Euclid, gravitational-wave standard sirens, and next-generation cosmological surveys. These results provide a possible geometric interpretation of the Hubble tension and establish a new observational validation pathway for Unified Fractal Quantum Field Theory.
Publication Date: 2026-06-23