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arXiv · 2609.26553

Constraining Inflation with Little Red Dots

Dionysios Karagiannis·P. Daniel Meerburg
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Abstract

Primordial non-Gaussianity is a direct probe of the physics of inflation. The tightest bounds still come from the cosmic microwave background, but large-scale structure is rapidly catching up: its intrinsically three-dimensional maps contain far more modes, provided the tracer combines large volume, high redshift, strong bias and sufficient number density. The Little Red Dots (LRDs) discovered by JWST plausibly offer all four. Inspired by recent work on BAO measurements using LRDs we forecast the joint galaxy power spectrum and bispectrum of a $14{,}000\,{\rm deg}^2$ LRD spectroscopic survey over $4<z<9$, marginalising over $32$ nuisance parameters and including the non-Gaussian bispectrum covariance. We find $σ(f_{\mathrm{NL}}^{\mathrm{loc}})=0.32$, $σ(f_{\mathrm{NL}}^{\mathrm{equil}})=32$ and $σ(f_{\mathrm{NL}}^{\mathrm{orth}})=10$, improving on Planck by factors of $16$, $1.5$ and $2.3$. The local bound lies a factor of three below the $σ(f_{\mathrm{NL}}^{\mathrm{loc}})\simeq1$ threshold that separates broad classes of single- and multi-field inflation. LRD clustering therefore has the potential to become an important probe of inflation, and makes a strong case for future wide-field near- to mid-infrared spectroscopy.

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Dionysios Karagiannis, P. Daniel Meerburg. 2026-09-22. Constraining Inflation with Little Red Dots. https://arxiv.org/abs/2609.26553

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