Speaker
Description
Recent detections of parity violation in cosmological observations, such as galaxy clustering and cosmic microwave background anisotropies, suggest the existence of parity-violating sources in the universe. To properly extract these signals from future cosmological experiments, a thorough analysis of parity-violating signatures and exploration of relevant models are essential. In this talk, we focus on galaxy clustering, which offers a window into parity violation through the analysis of the four-point correlation function, or its Fourier counterpart, the trispectrum. Specifically, we consider primordial magnetic fields (PMFs) generated during inflation as a source of parity violation. PMFs have attracted much attention in recent years as a potential origin of the observed large-scale magnetic fields. It is known that the anisotropic stress of PMFs can act as a source of curvature perturbations on superhorizon scales, called the passive scalar mode. Consequently, the helical components of the PMFs, which represent the parity-violating part, can be probed via the galaxy four-point correlation function. To investigate cosmological parity violation from PMFs, we first derive the trispectrum of galaxy density fields induced by the anisotropic stress of PMFs by employing a pole approximation. Our results confirm that the crosstalk between non-helical and helical PMFs is essential to produce a non-zero imaginary component in the trispectrum, which is a probe of the parity violation signal. We will present some discussion on what configurations in Fourier space of the parity-odd signals are enhanced. With our analytical and numerical results, we will provide a better constraint on the amplitude of helical PMFs from the future cosmological observations such as the galaxy trispectrum.
