This paper presents a detailed analysis of the axion dark matter mass based on numerical simulations of global string networks in the post-inflationary Peccei-Quinn symmetry breaking scenario. The study focuses on the axion emission spectrum from cosmic strings and its dependence on parameters such as string tension and initial conditions. Using large-scale lattice simulations with up to 11264³ lattice sites, the authors investigate the spectral index of axion emission and the effects of discretisation, oscillations, and initial conditions on the results. They find that the spectral index increases with string tension, but the exact behavior at large tensions remains uncertain due to discretisation effects. The axion dark matter mass is predicted to be in the range of 95–450 μeV, considering uncertainties in the spectral index and other systematics. The study highlights the importance of understanding the axion emission spectrum for experimental detection and provides insights into the behavior of global string networks in the early universe. The results suggest that the axion dark matter mass is a key parameter for future experiments and theoretical models.This paper presents a detailed analysis of the axion dark matter mass based on numerical simulations of global string networks in the post-inflationary Peccei-Quinn symmetry breaking scenario. The study focuses on the axion emission spectrum from cosmic strings and its dependence on parameters such as string tension and initial conditions. Using large-scale lattice simulations with up to 11264³ lattice sites, the authors investigate the spectral index of axion emission and the effects of discretisation, oscillations, and initial conditions on the results. They find that the spectral index increases with string tension, but the exact behavior at large tensions remains uncertain due to discretisation effects. The axion dark matter mass is predicted to be in the range of 95–450 μeV, considering uncertainties in the spectral index and other systematics. The study highlights the importance of understanding the axion emission spectrum for experimental detection and provides insights into the behavior of global string networks in the early universe. The results suggest that the axion dark matter mass is a key parameter for future experiments and theoretical models.