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Register a new userExploring Early Dark Energy solution to the Hubble tension with Planck and SPTPol data
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Anton Chudaykin A. S.
Publication date
2020
fields
Physics
and research's language is
English
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A promising idea to resolve the long standing Hubble tension is to postulate a new subdominant dark-energy-like component in the pre-recombination Universe which is traditionally termed as the Early Dark Energy (EDE). However, as shown in Refs. cite{Hill:2020osr,Ivanov:2020ril} the cosmic microwave background (CMB) and large-scale structure (LSS) data impose tight constraints on this proposal. Here, we revisit these strong bounds considering the Planck CMB temperature anisotropy data at large angular scales and the SPTPol polarization and lensing measurements. As advocated in Ref. cite{Chudaykin:2020acu}, this combined data approach predicts the CMB lensing effect consistent with the $Lambda$CDM expectation and allows one to efficiently probe both large and small angular scales. Combining Planck and SPTPol CMB data with the full-shape BOSS likelihood and information from photometric LSS surveys in the EDE analysis we found for the Hubble constant $H_0=69.79pm0.99,{rm km,s^{-1}Mpc^{-1}}$ and for the EDE fraction $f_{rm EDE}<0.094,(2sigma)$. These bounds obtained without including a local distance ladder measurement of $H_0$ (SH0ES) alleviate the Hubble tension to a $2.5sigma$ level. Including further the SH0ES data we obtain $H_0=71.81pm1.19,{rm km,s^{-1}Mpc^{-1}}$ and $f_{rm EDE}=0.088pm0.034$ in full accordance with SH0ES. We also found that a higher value of $H_0$ does not significantly deteriorate the fit to the LSS data. Overall, the EDE scenario is (though weakly) favoured over $Lambda$CDM even after accounting for unconstrained directions in the cosmological parameter space. We conclude that the large-scale Planck temperature and SPTPol polarization measurements along with LSS data do not rule out the EDE model as a resolution of the Hubble tension. This paper underlines the importance of the CMB lensing effect for robust constraints on the EDE scenario.
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New Early Dark Energy (NEDE) is a component of vacuum energy at the electron volt scale, which decays in a first-order phase transition shortly before recombination [arXiv:1910.10739]. The NEDE component has the potential to resolve the tension between recent local measurements of the expansion rate of the Universe using supernovae (SN) data and the expansion rate inferred from the early Universe through measurements of the cosmic microwave background (CMB) when assuming $Lambda$CDM. We discuss in depth the two-scalar field model of the NEDE phase transition including the process of bubble percolation, collision, and coalescence. We also estimate the gravitational wave signal produced during the collision phase and argue that it can be searched for using pulsar timing arrays. In a second step, we construct an effective cosmological model, which describes the phase transition as an instantaneous process, and derive the covariant equations that match perturbations across the transition surface. Fitting the cosmological model to CMB, baryonic acoustic oscillations and SN data, we report $H_0 = 69.6^{+1.0}_{-1.3} , textrm{km}, textrm{s}^{-1}, textrm{Mpc}^{-1}$ $(68 %$ C.L.) without the local measurement of the Hubble parameter, bringing the tension down to $2.5, sigma$. Including the local input, we find $H_0 = 71.4 pm 1.0 , textrm{km}, textrm{s}^{-1}, textrm{Mpc}^{-1}$ $(68 %$ C.L.) and strong evidence for a non-vanishing NEDE component with a $simeq 4, sigma$ significance.
The Hubble tension might be resolved by injecting a new energy component, called Early Dark Energy (EDE), prior to recombination. An Anti-de Sitter (AdS) phase around recombination can make the injected energy decay faster, which thus allows a higher EDE fraction (so larger $H_0$) while prevents degrading the CMB fit. In this work, we test the AdS-EDE model with CMB and Large-Scale Structure (LSS) data. Our CMB dataset consists of low-$ell$ part of Planck TT spectrum and SPTpol polarization and lensing measurements, since this dataset predicts the CMB lensing effect consistent with $Lambda$CDM expectation. Combining it with BAO and Pantheon data, we find the bestfit values $H_0=71.92$ km/s/Mpc and $H_0=73.29$ km/s/Mpc without and with the SH0ES prior, respectively. Including cosmic shear and galaxy clusters data, we have $H_0=71.87$ km/s/Mpc and $S_8=0.785$, i.e. only $1.3sigma$ discrepancy with direct $S_8$ measurement.
Early dark energy (EDE) offers a particularly interesting theoretical approach to the Hubble tension, albeit one that introduces its own set of challenges, including a new `why then problem related to the EDE injection time at matter-radiation equality, and a mild worsening of the large-scale structure (LSS) tension. Both these challenges center on the properties of dark matter, which becomes the dominant component of the Universe at EDE injection and is also responsible for seeding LSS. Motivated by this, we explore the potential of couplings between EDE and dark matter to address these challenges, focusing on a mechanism similar to chameleon dark energy theories, deeming this chameleon early dark energy (CEDE). We study the cosmological implications of such theories by fitting to the CMB, BAO, supernovae and the local value of $H_0$. We find that the Hubble tension is resolved by CEDE with $H_0 = 71.19(71.85)pm 0.99$ km/s/Mpc. Further, the model provides an excellent fit to all the data, with no change to the CMB $chi^2$ relative to a $Lambda$CDM fit to just the CMB, BAO and SNe (i.e. excluding the $H_0$ tension for $Lambda$CDM). We find a mild preference $(sim 2sigma)$ for the chameleon coupling constant $beta >0$.
Early Dark Energy (EDE) contributing a fraction $f_{rm EDE}(z_c)sim 10 %$ of the energy density of the universe around $z_csimeq 3500$ and diluting as or faster than radiation afterwards, can provide a resolution to the Hubble tension, the $sim 5sigma$ discrepancy between the $H_0$ value derived from early- and late-universe observations within $Lambda$CDM. However, it has been pointed out that Large-Scale Structure (LSS) data, which are in $sim3sigma$ tension with $Lambda$CDM and EDE cosmologies, might alter these conclusions. We reassess the viability of the EDE against a host of high- and low-redshift measurements, by combining LSS observations from recent weak lensing (WL) surveys with CMB, Baryon Acoustic Oscillation (BAO), growth function (FS) and Supernova Ia (SNIa) data. Introducing a model whose only parameter is $f_{rm EDE}(z_c)$, we report a $sim 2sigma$ preference for non-zero $f_{rm EDE}(z_c)$ from Planck data alone and the tension with SH0ES is reduced below $2sigma$. Adding BAO, FS and SNIa does not affect this result, while the inclusion of a prior on $H_0$ from SH0ES increase the preference for non-zero EDE to $sim3.6sigma$. After checking the EDE non-linear matter power spectrum predicted by standard semi-analytical algorithms via a set of $N$-body simulations, we show that current WL data do not rule out EDE. We also caution against the interpretation of constraints obtained from combining statistically inconsistent data sets within the $Lambda$CDM cosmology. In light of the CMB lensing anomalies, we show that the lensing-marginalized CMB data also favor non-zero $f_{rm EDE}(z_c)$ at $sim2sigma$, predicts $H_0$ in $1.4sigma$ agreement with SH0ES and $S_8$ in $1.5sigma$ ($0.8sigma$) agreement with KV (DES) data. Alternatively, we discuss promising extensions of the EDE cosmology that could allow to fully restore cosmological concordance.
Quantifying tensions -- inconsistencies amongst measurements of cosmological parameters by different experiments -- has emerged as a crucial part of modern cosmological data analysis. Statistically-significant tensions between two experiments or cosmological probes may indicate new physics extending beyond the standard cosmological model and need to be promptly identified. We apply several tension estimators proposed in the literature to the Dark Energy Survey (DES) large-scale structure measurement and Planck cosmic microwave background data. We first evaluate the responsiveness of these metrics to an input tension artificially introduced between the two, using synthetic DES data. We then apply the metrics to the comparison of Planck and actual DES Year 1 data. We find that the parameter differences, Eigentension, and Suspiciousness metrics all yield similar results on both simulated and real data, while the Bayes ratio is inconsistent with the rest due to its dependence on the prior volume. Using these metrics, we calculate the tension between DES Year 1 $3times 2$pt and Planck, finding the surveys to be in $sim 2.3sigma$ tension under the $Lambda$CDM paradigm. This suite of metrics provides a toolset for robustly testing tensions in the DES Year 3 data and beyond.
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