Dilaton backreaction on an anomaly-inspired axion potential generates a closed-form Lambert-W flattened hilltop, giving r ≈ 0.033–0.036 and α_s ≈ −4.6×10^{-4} at N=56 with strictly adiabatic dynamics.
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The Atacama Cosmology Telescope: DR6 Power Spectra, Likelihoods and $\Lambda$CDM Parameters
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abstract
We present power spectra of the cosmic microwave background (CMB) anisotropy in temperature and polarization, measured from the Data Release 6 maps made from Atacama Cosmology Telescope (ACT) data. These cover 19,000 deg$^2$ of sky in bands centered at 98, 150 and 220 GHz, with white noise levels three times lower than Planck in polarization. We find that the ACT angular power spectra estimated over 10,000 deg$^2$, and measured to arcminute scales in TT, TE and EE, are well fit by the sum of CMB and foregrounds, where the CMB spectra are described by the $\Lambda$CDM model. Combining ACT with larger-scale Planck data, the joint P-ACT dataset provides tight limits on the ingredients, expansion rate, and initial conditions of the universe. We find similar constraining power, and consistent results, from either the Planck power spectra or from ACT combined with WMAP data, as well as from either temperature or polarization in the joint P-ACT dataset. When combined with CMB lensing from ACT and Planck, and baryon acoustic oscillation data from DESI DR1, we measure a baryon density of $\Omega_b h^2=0.0226\pm0.0001$, a cold dark matter density of $\Omega_c h^2=0.118\pm0.001$, a Hubble constant of $H_0=68.22\pm0.36$ km/s/Mpc, a spectral index of $n_s=0.974\pm0.003$, and an amplitude of density fluctuations of $\sigma_8=0.813\pm0.005$. Including the DESI DR2 data tightens the Hubble constant to $H_0=68.43\pm0.27$ km/s/Mpc; $\Lambda$CDM parameters agree between the P-ACT and DESI DR2 data at the $1.6\sigma$ level. We find no evidence for excess lensing in the power spectrum, and no departure from spatial flatness. The contribution from Sunyaev-Zel'dovich (SZ) anisotropy is detected at high significance; we find evidence for a tilt with suppressed small-scale power compared to our baseline SZ template spectrum, consistent with hydrodynamical simulations with feedback.
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- abstract We present power spectra of the cosmic microwave background (CMB) anisotropy in temperature and polarization, measured from the Data Release 6 maps made from Atacama Cosmology Telescope (ACT) data. These cover 19,000 deg$^2$ of sky in bands centered at 98, 150 and 220 GHz, with white noise levels three times lower than Planck in polarization. We find that the ACT angular power spectra estimated over 10,000 deg$^2$, and measured to arcminute scales in TT, TE and EE, are well fit by the sum of CMB and foregrounds, where the CMB spectra are described by the $\Lambda$CDM model. Combining ACT with
- dataset [24] SPT-3G Collaboration, E. Camphuis et al., SPT-3G D1: CMB temperature and polarization power spectra and cosmology from 2019 and 2020 observations of the SPT-3G Main field, arXiv:2506.20707. [25] SPT-3G Collaboration, W. Quan et al., SPT-3G D1: Maps of the millimeter-wave sky from 2019 and 2020 observations of the SPT-3G Main field , arXiv:2603.20163. [26] ACT Collaboration, Thibaut Louis et al., The Atacama Cosmology Telescope: DR6 Power Spectra, Likelihoods and ΛCDM Parameters, arXiv:2503.
- dataset 1 E QUATION OF MOTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 A.2 E QUATION -OF-STATE PARAMETERS . . . . . . . . . . . . . . . . . . . . . . . . . 22 A.3 N UMBER OF E -F OLDINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 1 I NTRODUCTION The Data Release 6 (DR6) from the Atacama Cosmology Telescope (ACT) [1, 2] favors a slightly higher scalar spectral index, ns, than the one indicated from the Planck data [3] prompting renewed interest in inflationary m
- dataset CMB analyses reportn s = 0.9649±0.0042 (Planck 2018 TT,TE,EE+lowE)[1] and ln(10 10As) = 3.044±0.014 at k⋆ = 0.05 Mpc−1, withn s = 0.9665±0.0038 when adding lensing+BAO[1];B-mode polarization further constrains tensors (e.g.r 0.05 <0.036 at 95% C.L. from BICEP/Keck)[2], while ACT DR6 reportsn s = 0.9743±0.0034 and ln(1010As) = 3.053±0.013 for the P-ACT-LB combination[3]. Next, to make the Gauss-Bonnet imprint at the pivot more visible, the coupling parameters are updated toA= 0.9, ∆ = 0.45,p= 12,
- dataset • CMB: the CamSpec likelihood based on the Planck PR4 NPIPE high-multipole ( ℓ > 30) TT, TE, and EE spectra [ 77], together with the low-multipole temperature and E-mode polarization power spec- tra, C T T ℓ and C EE ℓ , derived using Commander and SimAll [78], respectively. We also include the CMB lensing likelihood constructed from the combina- tion of Planck PR4 NPIPE [ 79] and ACT DR6 [ 80]. • BAO: the DESI Y3 BAO measurements listed in Table IV of the DR2 paper [ 24]. TABLE I. Uniform prior
- dataset likelihood [29] while the polarization one is given bySroll2[30]. •Planck PR4:The Planck PR4 TTTEEE, i.e. CMB temperature, polarization, and cross-correlation measurements at high-ℓusing the NPIPE pipeline [31] over≈80 % of the sky. The data is based on theCamSpeclikelihood [32, 33] and covers 30≤ℓ≤2500. •ACT DR6:The Atacama Cosmology telescope (ACT) Data Release 6 (DR6) CMB TTTEEE measurements [34]. The DR6 maps cover almost half the sky, but only roughly half of that is used after masking the
- background Karam, and A. Racioppi, JCAP11, 014 (2020), arXiv:2006.09124 [gr-qc]. [52] J. Kim, Z. Yang, and Y.-l. Zhang, (2025), arXiv:2503.16907 [astro-ph.CO]. [53] J. Kim, X. Wang, Y.-l. Zhang, and Z. Ren, (2025), arXiv:2504.12035 [astro-ph.CO]. [54] A. S. Koshelev, K. S. Kumar, and A. A. Starobinsky, Int. J. Mod. Phys. D29, 2043018 (2020), arXiv:2005.09550 [hep-th]. [55] T. Louiset al.(ACT), arXiv preprint (2025), arXiv:2503.14452 [astro-ph.CO]. [56] E. Calabreseet al.(ACT), arXiv preprint (2025), arXiv:
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representative citing papers
DESI DR1 Lyman-alpha data yields Δ²★=0.379±0.032 and n★=-2.309±0.019 at k★=0.009 km⁻¹s and z=3, sharpening N_eff, α_s, and β_s constraints by factors of 1.18-1.90 when combined with other probes.
Scalar metric perturbations after inflation break conformal invariance and induce quantum production of gravitons, generating a GW spectrum that peaks near GHz frequencies for standard primordial scalar power spectra.
Hybrid inflation model with Z_N-symmetric waterfall fields cancels quadratic radiative corrections for any N and logarithmic ones for N>2, yielding a stable inflaton potential and domain-wall-free reheating via Higgs-portal couplings.
An interacting sterile neutrino component via pseudoscalar mediator reconciles CMB and DESI DR2 BAO measurements with 2.7 sigma preference and reduces H0 tension to 2.4 sigma.
A supergravity construction using two chiral superfields embeds arbitrary F(R) gravity as a UV completion of Starobinsky inflation, stabilized by the dilaton and consistent with swampland constraints in a heterotic string example.
Estimators from squeezed bispectrum and collapsed trispectrum recover unbiased small-scale matter power spectrum covariance at the percent level using 25 Quijote simulations.
Gaussian process regression on nuclear data predicts 10^5 D/H = 2.442 ± 0.040, 1.70 sigma below observation and consistent with first-principles calculations.
kSZ measurements constrain the gravitational acceleration between galaxy halos to follow g ∝ 1/r^{2.1±0.3}, consistent with Newtonian gravity in ΛCDM.
Two-field axion-like early dark energy reduces Hubble tension to 1.5 sigma residual and improves high-ell CMB fits over single-field models.
A Gompertzian reionization model with three nuisance parameters demotes optical depth to a derived quantity, reducing its uncertainty by a factor of three and revealing potential neutrino mass tension in CMB analyses.
A phase-space gating function μ(φ,X) localizes Gauss-Bonnet contributions to a finite e-fold window in inflation while preserving ghost and gradient stability for scalar and tensor modes.
A new quintessence model with non-minimal coupling produces an effective sign-switching interaction that fits current data better than LambdaCDM or w0waCDM and accounts for late-time dark energy weakening without phantom crossing.
KiDS-Legacy weak lensing plus CMB data yields a 3 sigma deviation in light deflection from GR in a Lambda CDM background, with the signal driven by large-scale CMB lensing amplitudes.
Nonminimal derivative coupling realizes the Harrison-Zeldovich attractor for monomial, hilltop, and α-attractor E-models, pulling them to the scale-invariant spectrum suggested by ACT data.
Proposes an FRB-based estimator F_G combining galaxy-DM and weak-lensing cross-correlations to measure G_light at ~10% precision in 10 redshift bins at z≲1 under a conservative k-cut.
No evidence for primordial hotspots in Planck polarization data leads to improved bounds on inflationary particle production couplings for light particles.
Minimal setup with one RHN and Higgs inflaton generates neutrino masses, baryon asymmetry via Affleck-Dine leptogenesis, and matches PLANCK/ACT inflation data with a small parameter space.
A sign-switching dark energy model (Λ_s CDM) recovers positive effective neutrino masses (0.055 ± 0.050 eV) consistent with oscillation data, unlike ΛCDM which prefers negative values (-0.075 eV), for DESI DR2 + CMB + supernova fits with z_† > 2.4.
Inflaton accretion during reheating drives non-linear PBH mass growth that extends lifetimes and amplifies emitted SGWB by multiple orders of magnitude.
Positive running of the spectral index is achievable in Einstein-Gauss-Bonnet gravity with viable inflation, unlike standard scalar field and F(R) models which face challenges.
Ward identities from large gauge symmetry impose model-independent constraints on renormalizing inflationary loops and non-perturbatively govern the infrared power spectrum evolution.
Naive nonlinear modelling of non-cold matter produces an artificial preference for a subdominant ultralight axion dark matter component at m ≈ 10^{-24} eV via a lensing-like enhancement in the CMB power spectrum.
Einstein-Cartan pseudoscalaron inflation coupled to type-I seesaw neutrinos makes nonthermal leptogenesis a necessary mechanism for the baryon asymmetry, yielding ns ~ 0.97, r ~ 0.004 and nB/s ~ 8.7e-11 for gamma ~ -1/100 and lightest Majorana mass ~ 10^13 GeV.
citing papers explorer
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Dilaton-Flattened Axion Inflation
Dilaton backreaction on an anomaly-inspired axion potential generates a closed-form Lambert-W flattened hilltop, giving r ≈ 0.033–0.036 and α_s ≈ −4.6×10^{-4} at N=56 with strictly adiabatic dynamics.
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Cosmological analysis of the DESI DR1 Lyman alpha 1D power spectrum
DESI DR1 Lyman-alpha data yields Δ²★=0.379±0.032 and n★=-2.309±0.019 at k★=0.009 km⁻¹s and z=3, sharpening N_eff, α_s, and β_s constraints by factors of 1.18-1.90 when combined with other probes.
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Quantum production of gravitational waves after inflation
Scalar metric perturbations after inflation break conformal invariance and induce quantum production of gravitons, generating a GW spectrum that peaks near GHz frequencies for standard primordial scalar power spectra.
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Pseudo-Nambu-Goldstone inflation with $Z_N$ symmetric waterfall fields
Hybrid inflation model with Z_N-symmetric waterfall fields cancels quadratic radiative corrections for any N and logarithmic ones for N>2, yielding a stable inflaton potential and domain-wall-free reheating via Higgs-portal couplings.
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Recoupled Dark Radiation reconciling CMB and DESI BAO measurements
An interacting sterile neutrino component via pseudoscalar mediator reconciles CMB and DESI DR2 BAO measurements with 2.7 sigma preference and reduces H0 tension to 2.4 sigma.
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Ultraviolet completion of Starobinsky inflation
A supergravity construction using two chiral superfields embeds arbitrary F(R) gravity as a UV completion of Starobinsky inflation, stabilized by the dilaton and consistent with swampland constraints in a heterotic string example.
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If at First You Don't Succeed, Trispectrum: I. Estimating the Matter Power Spectrum Covariance with Higher-Order Statistics
Estimators from squeezed bispectrum and collapsed trispectrum recover unbiased small-scale matter power spectrum covariance at the percent level using 25 Quijote simulations.
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A data-driven prediction for the primordial deuterium abundance
Gaussian process regression on nuclear data predicts 10^5 D/H = 2.442 ± 0.040, 1.70 sigma below observation and consistent with first-principles calculations.
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The Atacama Cosmology Telescope: A Test of the Gravitational Force Law on Cosmological Scales Using the Kinematic Sunyaev-Zeldovich Effect
kSZ measurements constrain the gravitational acceleration between galaxy halos to follow g ∝ 1/r^{2.1±0.3}, consistent with Newtonian gravity in ΛCDM.
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Double the axions, half the tension: multi-field early dark energy eases the Hubble tension
Two-field axion-like early dark energy reduces Hubble tension to 1.5 sigma residual and improves high-ell CMB fits over single-field models.
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Into the Gompverse: A robust Gompertzian reionization model for CMB analyses
A Gompertzian reionization model with three nuisance parameters demotes optical depth to a derived quantity, reducing its uncertainty by a factor of three and revealing potential neutrino mass tension in CMB analyses.
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Beyond $f(\phi)\mathcal{G}$: Gauss--Bonnet inflation with $\mu(\phi,X)$
A phase-space gating function μ(φ,X) localizes Gauss-Bonnet contributions to a finite e-fold window in inflation while preserving ghost and gradient stability for scalar and tensor modes.
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Non-minimally coupled quintessence with sign-switching interaction
A new quintessence model with non-minimal coupling produces an effective sign-switching interaction that fits current data better than LambdaCDM or w0waCDM and accounts for late-time dark energy weakening without phantom crossing.
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Evidence for deviation in gravitational light deflection from general relativity at cosmological scales with KiDS-Legacy and CMB lensing
KiDS-Legacy weak lensing plus CMB data yields a 3 sigma deviation in light deflection from GR in a Lambda CDM background, with the signal driven by large-scale CMB lensing amplitudes.
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Harrison-Zeldovich attractor: From Planck to ACT results
Nonminimal derivative coupling realizes the Harrison-Zeldovich attractor for monomial, hilltop, and α-attractor E-models, pulling them to the scale-invariant spectrum suggested by ACT data.
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Cavendish experiment with fast radio bursts on cosmological scales
Proposes an FRB-based estimator F_G combining galaxy-DM and weak-lensing cross-correlations to measure G_light at ~10% precision in 10 redshift bins at z≲1 under a conservative k-cut.
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Constraining Inflationary Particle Production with CMB Polarization
No evidence for primordial hotspots in Planck polarization data leads to improved bounds on inflationary particle production couplings for light particles.
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Leptogenesis and neutrino mass with one right-handed neutrino and Higgs inflaton
Minimal setup with one RHN and Higgs inflaton generates neutrino masses, baryon asymmetry via Affleck-Dine leptogenesis, and matches PLANCK/ACT inflation data with a small parameter space.
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Negative neutrino mass or negative dark energy?
A sign-switching dark energy model (Λ_s CDM) recovers positive effective neutrino masses (0.055 ± 0.050 eV) consistent with oscillation data, unlike ΛCDM which prefers negative values (-0.075 eV), for DESI DR2 + CMB + supernova fits with z_† > 2.4.
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Inflaton Accretion onto Primordial Black Holes During Reheating
Inflaton accretion during reheating drives non-linear PBH mass growth that extends lifetimes and amplifies emitted SGWB by multiple orders of magnitude.
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Positive Running of the Spectral Index for Scalar Theory and Modified Gravity
Positive running of the spectral index is achievable in Einstein-Gauss-Bonnet gravity with viable inflation, unlike standard scalar field and F(R) models which face challenges.
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Fixing the Renormalization of Inflationary Loops via Ward Identities
Ward identities from large gauge symmetry impose model-independent constraints on renormalizing inflationary loops and non-perturbatively govern the infrared power spectrum evolution.
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Ultra-light axion constraints from Planck and ACT: the role of nonlinear modelling
Naive nonlinear modelling of non-cold matter produces an artificial preference for a subdominant ultralight axion dark matter component at m ≈ 10^{-24} eV via a lensing-like enhancement in the CMB power spectrum.
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Einstein-Cartan pseudoscalaron inflation, reheating and nonthermal leptogenesis
Einstein-Cartan pseudoscalaron inflation coupled to type-I seesaw neutrinos makes nonthermal leptogenesis a necessary mechanism for the baryon asymmetry, yielding ns ~ 0.97, r ~ 0.004 and nB/s ~ 8.7e-11 for gamma ~ -1/100 and lightest Majorana mass ~ 10^13 GeV.
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On the origin of the environmental step: A BayeSN view of the ZTF SN Ia DR2
BayeSN analysis of ZTF Type Ia supernovae confirms a ~0.1 mag intrinsic environmental step in standardized brightness that is not explained by differences in dust extinction properties.
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DESI and Gravitational Wave Constraints Challenge Quintessential {\alpha}-Attractor Inflation
Alpha-attractor quintessential inflation models are disfavored by DESI observations and Delta Neff limits from gravitational waves, as they predict an inconsistent scalar spectral index when the gravitational-wave abundance is constrained.
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The End of the First Act: Spectral Running, Interacting Dark Radiation, and the Hubble Tension in Light of ACT DR6 Data
Including spectral running α_s, β_s and self-interacting dark radiation relaxes the ACT DR6 bound on ΔN_eff to <0.58 and lowers the Hubble tension to 2.2σ with three extra parameters.
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Do equation of state parametrizations of dark energy faithfully capture the dynamics of the late universe?
Node-based reconstruction of cosmic expansion prefers stronger deceleration at z≈1.7 than smooth DE EoS parametrizations, isolating z~1.5-2 as a window where the latter may compress localized kinematic features permitted by current data.
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FolpsD: combining EFT and phenomenological approaches for joint power spectrum and bispectrum analyses
FolpsD combines EFT power spectrum and tree-level bispectrum with damping to enable joint analyses that improve cosmological constraints from DESI-like galaxy mocks by up to 30% on As and omega_cdm while extending the usable k-range without significant biases for LRG samples.
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Disentangling cosmic distance tensions with early and late dark energy
Early dark energy resolves CMB-BAO tension and, combined with thawing quintessence, reduces overall cosmological tensions without phantom crossing.
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Is the $w_0w_a$CDM cosmological parameterization evidence for dark energy dynamics partially caused by the excess smoothing of Planck PR4 CMB anisotropy data?
Planck PR4 CMB data mildly favors dynamical dark energy, but this preference weakens when accounting for possible excess smoothing, indicating the signal may partly arise from data processing issues.
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Measuring neutrino mass in light of ACT DR6 and DESI DR2
New ACT and DESI data yield model-dependent upper limits on sum of neutrino masses, with holographic dark energy giving the tightest bounds and a consistent preference for degenerate hierarchy.
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Probing Dynamical Dark Energy with Late-Time Data: Evidence, Tensions, and the Limits of the $w_0w_a$CDM Framework
Evidence for dynamical dark energy in the w0waCDM framework is strongly dataset-dependent, driven by mismatches in low-redshift BAO distance ratios that produce divergent expansion histories and inconsistent Hubble tension relief.
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Self-resonance preheating in deformed attractor models: oscillon formation and evolution
Deformed alpha-attractor T-models with a Gaussian feature near the minimum yield more smaller shorter-lived oscillons during self-resonance preheating, suppressing energy in oscillons and altering the high-frequency gravitational wave tail while leaving low frequencies unchanged.
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Revisiting the Matter Creation Process: Observational Constraints on Gravitationally Induced Dark Energy and the Hubble Tension
Gravitationally induced particle creation models fit cosmological data as well as ΛCDM and reduce the Hubble tension from 4.3σ to 2.4–3σ.
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Thawing Quintessence: Priors, evidence, and likely trajectories
Bayesian evidence from DESI DR2 BAO, Planck+ACT CMB, and multiple supernova samples favors thawing quintessence over a cosmological constant.
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Echoes of $R^3$ modification and Goldstone preheating in the CMB-BAO landscape
An R^3 modification to R^2-Higgs inflation fits the high n_s by inducing Goldstone preheating that reconciles CMB and inflationary energy scales.
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Curvaton-assisted hilltop inflation
Curvaton coupling relaxes initial tuning in hilltop inflation and revives the sub-Planckian quartic model while remaining consistent with cosmological observations.
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The implications of inflation for the last ACT
A parameterized slow-roll model and a new exponential f(R) inflation model are constrained by P-ACT-LB-BK18 data, with the latter aligning to the ACT scalar spectral index preference in both standard and EDE frameworks.
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SPT-3G D1: Axion Early Dark Energy with CMB experiments and DESI
CMB-only data give f_EDE < 0.07 at 95% CL with no strong AEDE signal, while CMB+DESI yields f_EDE = 0.055^{+0.024}_{-0.047} at 68% CL and lowers Hubble tension to 2.6 sigma.
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Equation of state during (p)reheating with trilinear interactions
Lattice simulations show that the post-inflationary equation of state with trilinear interactions returns to zero after an initial deviation, substantially lowering stochastic gravitational wave amplitudes relative to prior estimates.
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Stable initial conditions and analytical investigations of cosmological perturbations in a modified loop quantum cosmology
A stable initial state is identified in mLQC-I that diagonalizes the Hamiltonian and minimizes particle creation, with mode functions approximated analytically by Airy or cylindrical functions whose constants are fixed by that state.
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ACT-ing on inflation: Implications of non Bunch-Davies initial condition and reheating on single-field slow roll models
Non-Bunch-Davies initial conditions substantially improve the fit of various single-field slow-roll inflation models to updated n_s-r constraints from ACT DR6 combined with Planck, DESI, and BICEP/Keck data.
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Constraints on primordial non-Gaussianity from Quaia
Reports f_NL = -20.5^{+19.0}_{-18.1} (68% CL) from combined Quaia quasar auto-correlation and CMB lensing cross-correlation assuming p_phi=1, or -28.7^{+26.1}_{-24.6} for p_phi=1.6.
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DEMNUni: the Sunyaev-Zel'dovich effect in the presence of massive neutrinos and dynamical dark energy
N-body simulations show the log Compton-y distribution mean decreases linearly with neutrino fraction (slope ~10 f_ν) and tSZ power spectrum scales as power law in σ8^cb (exponents 7.3-8.1), with ∑m_ν=0.16 or 0.32 eV fitting Planck data better than massless case.
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Warm inflation in Weyl geometric gravity
Warm inflation with linear dissipation and quartic potential is realized in Weyl geometric gravity, incorporating the Weyl vector to produce a smooth transition to radiation domination with observables consistent with ACT data.
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Single field matter bounce with dark energy era: comparison with CMB Planck 2018 data and best fit parameters
A matter bounce model driven by a scalar field with exponential potential fits Planck 2018 CMB data comparably to inflationary ΛCDM, with the potential slope λ directly setting the scalar spectral index ns.
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F-Term Hybrid Inflation with T-Model K\"ahler Geometry and Beyond
F-term hybrid inflation with SU(1,1)/U(1) or SU(2)/U(1) Kähler geometry in GUTs can be realized without inflationary extrema for broad parameters, matching ACT/SPT data via curvature and tadpole adjustments while predicting cosmic string gravitational waves.
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The Status of Gravitational Vector Perturbations with Recent CMB Data
Recent CMB datasets tighten 95% CL upper bounds on vector-mode amplitude r_v to 1.3e-4 (neutrino isocurvature), 6.8 (octupole), and 4.2 (sourced) at k=0.05 Mpc^-1, with no significant detection.
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String-inspired Gauss-Bonnet Gravity Inflation and ACT
MCMC analysis of sixteen ghost-free f(R,G) inflation models shows all reproduce ns ≈ 0.97 at 60 e-folds with stable μ ≈ 0.1, preference set by Hubble parametrization.