Detecting higher spin fields through statistical anisotropy in the CMB and galaxy power spectra

TL;DR

This paper explores how higher spin fields during inflation induce distinctive statistical anisotropies in the CMB and galaxy spectra, with potential detectability if their signals exceed a small threshold.

Contribution

It demonstrates that higher spin fields cause unique anisotropic signatures in the power spectrum, including higher-order coefficients, and forecasts their detectability in upcoming surveys.

Findings

Higher spin fields induce nonvanishing higher-order anisotropy coefficients.

Detectability of anisotropy coefficients is feasible if their magnitude exceeds ~10^{-3}.

All coefficients could be detected in near future if sufficiently large.

Abstract

Primordial inflation may represent the most powerful collider to test high-energy physics models. In this paper we study the impact on the inflationary power spectrum of the comoving curvature perturbation in the specific model where massive higher spin fields are rendered effectively massless during a de Sitter epoch through suitable couplings to the inflaton field. In particular, we show that such fields with spin $s$ induce a distinctive statistical anisotropic signal on the power spectrum, in such a way that not only the usual $g_{2M}$-statistical anisotropy coefficients, but also higher-order ones (i.e., $g_{4M}$, $g_{6M}$, $\cdots$, $g_{(2s-2)M}$ and $g_{(2s) M}$) are nonvanishing. We examine their imprints in the cosmic microwave background and galaxy power spectra. Our Fisher matrix forecasts indicate that the detectability of $g_{LM}$ depends very weakly on $L$: all coefficients could be detected in near future if their magnitudes are bigger than about $10^{-3}$.