Isocurvature Constraints and Gravitational Ward Identity

TL;DR

This paper examines the cross-correlation between curvature and isocurvature perturbations in axion and WIMPZILLA dark matter models, emphasizing the role of gravitational Ward identities in confirming previous assumptions.

Contribution

It demonstrates that the gravitational Ward identity ensures the negligible cross-correlation assumption in axion and WIMPZILLA scenarios.

Findings

Gravitational Ward identity confirms negligible cross-correlation.

Cross-correlation impacts isocurvature perturbation predictions.

Analysis applies to axion and WIMPZILLA dark matter models.

Abstract

Axions and WIMPZILLAs are well-motivated dark matter candidates with interesting cos- mological implications, such as isocurvature perturbations and non-Gaussianities. How- ever, these predicted implications in the literature are based on the assumption that the cross-correlation between curvature and CDM isocurvature is negligible. This contribution discusses the cross-correlation in the axion and the WIMPZILLA scenarios. Particularly, it is shown that the gravitational Ward identity associated with diffeomorphism invariance plays an important role in this cross-correlation calculation confirming the assumption.