Constraining the Primordial Intergalactic Magnetic Field in Cosmic Voids with the Density-Weighted Ariza Length

In this study, we present a novel methodological perspective for constraining the primordial intergalactic magnetic field by utilizing the architecture of cosmic voids. To achieve this, we analyze eighteen years of public data from the Fermi-LAT space telescope centered on a sample of BL Lacertae objects at low redshift, with special emphasis on the blazar Markarian 421. The method is based on the use of a line-of-sight length metric weighted by the non-linear density of void cores, allowing us to evaluate with high precision the potential presence of extended electromagnetic cascade emission. Our results rule out such extended emission across the analyzed targets and establish rigorous, unprecedented upper limits for the strength of the intergalactic magnetic field, providing a framework consistent with inflationary magnetogenesis models.