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

Understand

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.