Speaker
Description
Primordial magnetic fields are well motivated by the observations of the cosmic magnetic fields on various scales and have been attracting attention as a possible origin of the large-scale magnetism in the Universe. Several studies have also suggested that intergalactic magnetic fields may possess helicity, corresponding to an asymmetry between the right- and left-handed components. Since primordial magnetic fields can leave imprints on multiple observables, including the cosmic microwave background and galaxy distributions, they provide a phenomenological window into parity-violating physics in the early Universe. In this talk, we focus on parity-violating signatures in cosmological observables, in particular the trispectrum. We compute the trispectrum of the passive mode, which is the curvature perturbation induced by scale-invariant helical primordial magnetic fields on superhorizon scales, and evaluate its amplitudes in Fourier space. We show that the trispectrum is enhanced in the collapsed limit in equilateral configurations. Using current observational constraints on the local-type trispectrum, we derive a rough upper bound on the helical-to-non-helical ratio, defined as the ratio of the amplitudes of the helical and non-helical magnetic-field power spectra. Finally, we will also discuss the preliminary results for the EB correlation of galaxy intrinsic alignments sourced by helical primordial magnetic fields, which may provide a complementary observational probe of parity-violating signatures from primordial magnetism.
| Other topic / keywords: | Higher order statistics |
|---|