Year: 2025
Type: preprint
Abstract: We present observational constraints on large-scale white noise (LSWN) in the cosmic density field, a phenomenon predicted to arise from non-linear mode coupling during cosmological evolution. Building on the theoretical framework of Paper I, where we demonstrated that non-linearities inevitably redistribute power from small to large scales through mode mixing, we confront these predictions with current cosmological data. We modify the CLASS Boltzmann code to incorporate a white noise component $k_\mathrm{BH}/k$ in the primordial power spectrum and perform parameter estimation using current cosmological data. The non-detection of excess power on the largest observable scales places stringent upper bounds: $k_\mathrm{BH} \leq 1.80 \times 10^{-13}~\mathrm{Mpc}^{-1}$ at 99\% confidence. These constraints imply the primordial power spectrum must deviate from perfect scale invariance on small scales, either through a cutoff at $k_{\mathrm{cut}} \lesssim 3~\mathrm{pc}^{-1}$ or through running of the spectral index with $α_s \lesssim -0.015$. Our results demonstrate that LSWN provides a powerful probe of the primordial spectrum at scales orders of magnitude smaller than directly observable, offering unique constraints on early-universe physics.
Source: arXiv (Cornell University)
Authors: Barenboim, Gabriela, Ireland, Aurora, Stebbins, Albert
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: G1259785136, G1422035950, Theory For New Fundamental Physics Experiments, G1880773934, G2188020438, G2262748287, G2376186588, G3220251042, G3345895242, G3480869486, G425668148, G4861624602, G4950051987, G5017550144, G5391483016, G5574724152, G603324873, G6281504974, G6417970939, G6466192506, Research in Particle Theory, Cosmology, and Quantum Gravity, G7084143925, G716412294, G7169023097, G7584948965, G7984235579, G86560745, G8847342006
OpenAlex ID: W7106280684
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