Charged Loops at the Cosmological Collider with Chemical Potential

TL;DR

This work develops a chemical-potential mechanism for a pair of charged scalars during inflation and computes their one-loop bispectrum using a de Sitter spectral decomposition. The analysis isolates a non-analytic oscillatory signal in the squeezed limit, arising from the threshold μ12 = μ1+μ2, and identifies a smooth analytic background from resonance near μ ≈ λ; the signal scales as p^{-3 - i(λ-μ12)} with amplitude controlled by the chemical potential and masses. The authors show that f_{ obreakspace}{\mathrm{NL}} \, \sim \, \mathcal{O}(0.01) is achievable within theoretical control and could be probed by future 21cm tomography, with a concrete application to colored Higgs bosons in SU(5) orbifold SUSY GUTs with masses up to ~1.5×10^{15} GeV. They provide a detailed treatment of backgrounds, constraints, and higher-order corrections, and discuss extensions to other spins and broader EFT settings. The work lays a pathway for exploiting cosmological collider signals to test heavy charged states in high-scale theories.

Abstract

Cosmological collider physics allows the detection of heavy particles at inflationary scales through their imprints on primordial non-Gaussianities. We study the chemical potential mechanism applied to a pair of charged scalars. We analytically evaluate the resulting one-loop contribution to the bispectrum, using the spectral decomposition. In this way we are able to determine the parametric dependences for both the signal and the background. We show that a signal strength $f_{\mathrm{NL}}\sim O(0.01)$ can be obtained within theoretical control, potentially reachable by 21cm tomography. As an application we consider the colored Higgs bosons in $\mathrm{SU}(5)$ supersymmetric orbifold grand unification with masses $M\lesssim10^{15}\:\mathrm{GeV}$.

Figures (25)

• Figure 1: The shape of the momentum triangle and the two parameters. In the squeezed limit $p\gg1$, the angle parameter $\chi\simeq\cos\theta_1\simeq-\cos\theta_2$.
• Figure 2: The 1PI one-loop subdiagrams contributing at $\mathcal{O}\mathopen{}\left(\alpha^2\right)\mathclose{}\mathord{\newline}$. The solid dots, $\bullet$, represents $(+)$-type vertices, while the empty dots, $\circ$, represent $(-)$-type vertices.
• Figure 3: (Left) At $\mathcal{O}\mathopen{}\left(\alpha^2\right)\mathclose{}\mathord{\newline}$, there are only two types of topologies contributing to the 3-point function and both of them admit the spectral density representation. (Right) Triangle diagram contributions first appear at $\mathcal{O}\mathopen{}\left(\alpha^4\right)\mathclose{}\mathord{\newline}$. These contributions are subdominant though cannot be represented by a single spectral integral.
• Figure 4: The spectral representation of the 3-point correlator at one-loop. This diagram only shows one of the ways $\delta\phi$ can contract with $e^{\pm i\delta\phi/\Lambda}$.
• Figure 5: The de Sitter spectral density eq. (\ref{['eq:ds-spectral']}) compared with the Minkowski spectral density eq. (\ref{['eq:flat-spectral']}), and the near-threshold approximation eq. (\ref{['eq:ds-spectral-threshold']}), for $\mu_1=\mu_2=4$.