Large blue-tilted axionic isocurvature perturbations can arise when the axion sector is significantly out of equilibrium during inflation. Given that future galaxy surveys are probing shorter length scales with greater accuracy, blue isocurvature perturbations are natural targets for these surveys.
In this talk, we will first discuss the strongly blue tilted (nI~4) axionic isocurvature perturbations that are generated when the quantum oscillator modes are starting to be underdamped. Interestingly, there exist parametric regions with strong resonant spectral behavior that lead to diverse isocurvature spectral shapes and large amplitude enhancements of O(10-1000). Next, we will present Fisher forecasts for the Euclid and MegaMapper experiments in their ability to detect the CDM blue isocurvature signal. Some interesting features that arise in the EFTofLSS and bias expansion due to the blueness of the isocurvature spectrum will also be discussed.