Using SPT polarization, Planck 2015, and non-CMB data to constrain tilted spatially-flat and untilted nonflat ΛCDM , XCDM, and ϕCDM dark energy inflation cosmologies
Chan‐Gyung Park, Bharat Ratra · 2020 · 63 citationsRead the paper
We use six tilted spatially flat and untilted nonflat dark energy cosmological models in analyses of South Pole Telescope polarization (SPTpol) cosmic microwave background (CMB) data, alone and in combination with Planck 2015 CMB data and non-CMB data, namely, the Pantheon type Ia supernovae apparent magnitudes, a collection of baryon acoustic oscillation data points, Hubble parameter measurements, and growth rates. Although the cosmological models that best fit the Planck CMB and non-CMB data do not provide good fits to the SPTpol data, with the ${\ensuremath{\chi}}^{2}$'s exceeding the expected value, given the uncertainties, in each model the cosmological parameter constraints from the SPTpol data and from the Planck CMB and non-CMB data are largely mutually consistent. When the smaller angular scale SPTpol data are used jointly with either the Planck data alone or with the Planck CMB and the non-CMB data to constrain untilted nonflat models, spatially closed models remain favored over their corresponding flat limits. When used in conjunction with Planck data, non-CMB data (baryon acoustic oscillation measurements in particular, from six experiments) have significantly more constraining power than the SPTpol data.
What the full text shows
Shown in the lab- Parameter constraints from SPTpol data are largely mutually consistent with those from Planck CMB and non-CMB data across all six models. (Tilted spatially-flat and untilted non-flat ΛCDM, XCDM, and φCDM models)
- Spatially closed models are favored over spatially-flat limits when SPTpol data is used jointly with Planck data. (Untilted non-flat models)
- Non-CMB data, specifically BAO measurements from six experiments, provide significantly more constraining power than SPTpol data when used with Planck data. (Joint analysis with Planck data)
- Best-fit models from Planck CMB and non-CMB data do not provide good fits to SPTpol data. — χ2 exceeds expected value (All six studied cosmological models)
- Setup
- Data includes SPTpol (50 < ℓ ≤ 8000 over 500 deg2), Planck 2015 (TT+lowP), Pantheon Type Ia supernovae, BAO from six experiments, Hubble parameter measurements, and growth rates.
- How
- The researchers used the Markov chain Monte Carlo (MCMC) method via a modified CAMB/COSMOMC program to explore parameter spaces. They compared SPTpol CMB data (TE, EE, TE+EE) against Planck 2015 CMB data and non-CMB data (Pantheon SN, BAO, H(z), and growth rates).
- Limitations
- SPTpol data alone cannot tightly constrain reionization optical depth (τ), requiring a Gaussian prior. · SPTpol data alone does not tightly constrain dark energy parameters (w, α), H0, or Ωm in XCDM and φCDM models. · Non-flat models lack a determined power spectrum for non-slow-roll inflation.
Summarized by Gemma 4 from the open-access full text · 7 Oct 2026. Read it