The Knotted Sky I: Planck constraints on the primordial power spectrum

Journal Article · Fri Aug 01 04:00:00 EDT 2014 · Journal of Cosmology and Astroparticle Physics

DOI:https://doi.org/10.1088/1475-7516/2014/08/052· OSTI ID:22373375

Aslanyan, Grigor; Price, Layne C.; Easther, Richard ^[1]

---

1. Department of Physics, University of Auckland, Private Bag 92019, Auckland (New Zealand)

Using the temperature data from Planck we search for departures from a power-law primordial power spectrum, employing Bayesian model-selection and posterior probabilities. We parametrize the spectrum with n knots located at arbitrary values of logk, with both linear and cubic splines. This formulation recovers both slow modulations and sharp transitions in the primordial spectrum. The power spectrum is well-fit by a featureless, power-law at wavenumbers k>10{sup -3} Mpc{sup -1}. A modulated primordial spectrum yields a better fit relative to ΛCDM at large scales, but there is no strong evidence for a departure from a power-law spectrum. Moreover, using simulated maps we show that a local feature at k ∼ 10{sup -3} Mpc{sup -1} can mimic the suppression of large-scale power. With multi-knot spectra we see only small changes in the posterior distributions for the other free parameters in the standard ΛCDM universe. Lastly, we investigate whether the hemispherical power asymmetry is explained by independent features in the primordial power spectrum in each ecliptic hemisphere, but find no significant differences between them.

• OSTI ID: 22373375
• Journal Information: Journal of Cosmology and Astroparticle Physics, Journal Name: Journal of Cosmology and Astroparticle Physics Journal Issue: 08 Vol. 2014; ISSN 1475-7516
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASYMMETRY
MAPS
MODULATION
SIMULATION
SKY
SPECTRA
UNIVERSE
YIELDS