# Searching for Oscillations in the Primordial Power Spectrum with CMB and LSS Data

## TL;DR

This study searches for logarithmic oscillations in the primordial power spectrum using CMB and LSS data, finding a slight preference for the standard model but hinting at possible features that future data could clarify.

## Contribution

It introduces a search for primordial oscillations inspired by axion-monodromy models using combined CMB and LSS data, providing new constraints on oscillation parameters.

## Key findings

- Best-fit oscillation frequency at log10(ω)=1.5
- Improved fit over ΛCDM with Δχ² ≈ -9 to -13
- Bayesian evidence slightly favors ΛCDM

## Abstract

Different inflationary models predict oscillatory features in the primordial power spectrum. These can leave an imprint on both the cosmic microwave background (CMB) and the large-scale structure (LSS) of our Universe, that can be searched for with current data. Inspired by the axion-monodromy model of inflation, we search for primordial oscillations that are logarithmic in wavenumber, using both CMB data from the Planck satellite and LSS data from the WiggleZ galaxy survey. We find that, within our search range for the new oscillation parameters (amplitude, frequency and phase), both CMB-only and CMB+LSS data yield the same best-fit oscillation frequency of $\log_{10}\omega=1.5$, improving the fit over $\Lambda$CDM by $\Delta\chi^2\! =\! -9$ and $\Delta\chi^2\! =\! -13$ (roughly corresponding to $2\sigma$ and $2.8\sigma$ significance), respectively. Bayesian evidence for the log-oscillation model versus $\Lambda$CDM indicates a very slight preference for the latter. Future CMB and LSS data will further probe this scenario.