Constraints on Resonant Particle Production during Inflation from the Matter and CMB Power Spectra

TL;DR

This work investigates whether resonant production of Planck-scale particles during inflation can imprint measurable features on the matter and CMB power spectra. By parameterizing a two-parameter modification to the primordial spectrum and propagating it through transfer functions to both $P(k)$ and $C_\ell$, the authors fit to SDSS/2dF/Lyman-α data and to CMB measurements, finding largely marginal evidence for a feature with $k_* \sim 0.17$–$0.18\,h\mathrm{Mpc}^{-1}$ and amplitude $A \sim 0.35$–$0.7$, corresponding to a fermion mass $m \sim 1$–$2\,M_{\rm pl}$ and coupling $\lambda \sim 0.5$–$1$. The strongest matter feature near $k_* \sim 0.4\,h\mathrm{Mpc}^{-1}$ points to a similar interpretation with $m \approx 2.2\,M_{\rm pl}$ and $\lambda \approx 0.6$, but the significance is limited by data systematics and SZ contributions to the high-$\ell$ CMB. Overall, the results illustrate how precision small-scale power spectra could reveal Planck-scale physics, though robust confirmation awaits improved measurements of the primordial spectrum and SZ effects.

Abstract

We analyze the limits on resonant particle production during inflation based upon the power spectrum of fluctuations in matter and the cosmic microwave background. We show that such a model is consistent with features observed in the matter power spectrum deduced from galaxy surveys and damped Lyman-alpha systems at high redshift. It also provides an alternative explanation for the excess power observed in the power spectrum of the cosmic microwave background fluctuations in the range of 1000 < l < 3500. For our best-fit models, epochs of resonant particle creation reenter the horizon at wave numbers ~ 0.4 and/or 0.2 (h/Mpc). The amplitude and location of these features correspond to the creation of fermion species of mass ~ 1-2 Mpl during inflation with a coupling constant between the inflaton field and the created fermion species of near unity. Although the evidence is marginal, if this interpretation is correct, this could be one of the first observational hints of new physics at the Planck scale.

Figures (6)

• Figure 1: Comparison of the observed galaxy cluster function from SDSS [17], 2dF [18], and Lyman-$\alpha$ [19] with the spectrum implied from the fits to the matter power spectrum with (solid line) and without (dashed line) resonant particle creation during inflation as described in the text.
• Figure 2: Upper figure shows the CMB WMAP, ACBAR, and CBI data in the range $l = 10 - 5000$. The dashed line is the CMB power spectrum computed using the standard WMAP cosmological parameters. The thick solid line is for a best-fit to these data for a model with resonant particle production included. The lower figure shows an expanded view of the ACBAR, CBI, VSA, and BIMA data in the range of $l = 1000 - 7000$. The dashed line shows the standard WMAP result without the SZ effect included. The dot-dashed line shows our fit SZ contribution (from the analytic halo model of Ref. [14]). The solid line shows the best fit to these data sets with resonant particle production and the SZ effect included. The dot-dot-dashed line shows the resonant particle creation component without the SZ contribution.
• Figure 3: Constrains on parameters $A$ and $k_*$ from the fit to the matter power spectrum alone. Contours show 1 and 2 $\sigma$ confidence limits. The horizontal axis indicates $\log (k_*)$ where $k_*$ is in units of ($h$ Mpc$^{-1}$).
• Figure 4: Constrains on parameters $A$ and $k_*$ from the CMB power spectrum. Contours show 1 and 2$\sigma$ limits. The horizontal axis indicates $\log (k_*)$ where $k_*$ is in units of ($h$ Mpc$^{-1}$).
• Figure 5: Constrains on parameters $A$ and $k_*$ from a fit to the combined CMB and matter power spectra. Contours show 1 and $2 \sigma$ limits. The horizontal axis indicates $\log (k_*)$ where $k_*$ is in units of ($h$ Mpc$^{-1}$).