Eternal Inflation under Swampland Constraints: Narrow Paths to a Multiverse

We investigate the compatibility of eternal inflation with three recently proposed swampland-inspired criteria: the Further Refined de Sitter Swampland Conjecture (FRDSSC), the Scalar Weak Gravity Conjecture (SWGC), and the Strong Scalar Weak Gravity Conjecture (SSWGC). Our analysis reveals that while the FRDSSC permits eternal inflation within a narrow hilltop regime where quantum diffusion dominates over classical rolling near a tachyonic maximum the SWGC and SSWGC impose significantly stronger constraints. In single-field hilltop models, which we analyze in this work, these scalar weak gravity conditions are generically violated, thereby disfavoring eternal inflation unless additional fields, non-hilltop potential shapes, or multi-field dynamics are introduced. These results delineate a nuanced landscape in which eternal inflation can survive under refined de Sitter conditions but remains highly constrained by scalar weak gravity considerations within the class of models studied here. Importantly, our findings do not amount to an absolute exclusion of eternal inflation in all single field cases; rather, they indicate that eternal inflation is generically disfavored under the SWGC and SSWGC, with possible viable alternatives requiring specially constructed potentials or extended frameworks. This work provides critical insights into the interplay between quantum gravity, inflationary dynamics, and the string landscape.