Extending the Cosmological Collider: New Scaling Regimes and Constraints from BOSS

Primordial non-Gaussianity generated by additional fields during inflation offers a compelling observational target. Heavy fields imprint characteristic oscillatory signals in non-Gaussian correlation functions of the inflaton, a process sometimes referred to as cosmological-collider physics. These distinct signatures are compelling windows into ultra-high-energy physics, but are often suppressed, making standard equilateral non-Gaussianity the most promising discovery channel in many scenarios. In this paper, we show that direct couplings between the inflaton and additional fields can lead to a wide variety of novel, observationally relevant signals which open new parameter regimes that simultaneously exhibit the characteristics of light and heavy fields. We identify these primordial signatures in the late-time observables of the large-scale structure of the Universe, where they most significantly modify the scale-dependent bias of the galaxy power spectrum to include an oscillatory modulation around a non-trivial power law. We explore the full range of parameters that phenomenologically arise in these models and study the sensitivity of current and future galaxy surveys, finding that this new class of primordial non-Gaussianity is particularly accessible in near-term surveys due to its oscillatory feature. Finally, we perform an analysis of existing data from the final release of the Baryon Oscillation Spectroscopic Survey (BOSS DR12). While we find no evidence for a signal, we demonstrate significant improvements in sensitivity over respective non-oscillatory scenarios and place the first constraints on this extended parameter space of oscillatory non-Gaussianity.

💡 Research Summary

The paper investigates how direct couplings between the inflaton and additional scalar fields can modify the standard cosmological‑collider picture. In conventional quasi‑single‑field inflation, heavy fields generate oscillatory non‑Gaussianity that is doubly suppressed: by a Boltzmann factor e^{−πν} and by a (k₁/k₂)^{3/2} scaling in the squeezed limit, making detection unlikely. By allowing time‑dependent mixing that breaks de Sitter isometries, the authors introduce a complex scaling dimension Δ = α + iν with α < 3/2. This relaxes the power‑law suppression while preserving the logarithmic oscillation frequency ν, which is set by the field mass. The resulting primordial bispectrum induces a scale‑dependent bias in the galaxy power spectrum of the form b(k) ∝ k^{α−3/2} cos