An iterative AI reasoning process proposes new dynamical dark energy equations of state that are competitive with traditional forms on supernova, BAO, and Planck data.
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The Cosmic Linear Anisotropy Solving System (CLASS) II: Approximation schemes
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abstract
Boltzmann codes are used extensively by several groups for constraining cosmological parameters with Cosmic Microwave Background and Large Scale Structure data. This activity is computationally expensive, since a typical project requires from 10'000 to 100'000 Boltzmann code executions. The newly released code CLASS (Cosmic Linear Anisotropy Solving System) incorporates improved approximation schemes leading to a simultaneous gain in speed and precision. We describe here the three approximations used by CLASS for basic LambdaCDM models, namely: a baryon-photon tight-coupling approximation which can be set to first order, second order or to a compromise between the two; an ultra-relativistic fluid approximation which had not been implemented in public distributions before; and finally a radiation streaming approximation taking reionisation into account.
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representative citing papers
Bayesian reconstruction and exhaustive symbolic regression on CMB, BAO, and supernova data yield the one-parameter dark energy parametrization w(a) = w0 / sqrt(a) that fits observations comparably to CPL and better than LambdaCDM.
Derives exact rational-plus-π² closed forms for every multipole coefficient α_ℓ in the neutrino collision kernel by rewriting the kernel as angular derivatives of a Yukawa potential and reducing the integrals via a first-order recurrence.
Control variates with Zeldovich mocks reduce covariance matrix variance by up to an order of magnitude on large scales in DESI-like mocks.
The work demonstrates that multi-tracer field-level SBI on galaxy and HI maps yields 2-7 times better constraints on Omega_m and sigma_8 than single-tracer or summary-statistic approaches, with 3D maps performing best.
Any unified early and late dark energy scenario with a single tracking scalar field requires a potential with three distinct slopes arranged in a steep-steeper-shallow hierarchy.
A Newtonian Motion Gauge found via Einstein-Boltzmann solver maps linear dynamics with scale-dependent growth and GR corrections to Newtonian equations, enabling consistent nonlinear EFT calculations that are transformed back for accuracy in real and redshift space.
Second-order relativistic corrections to the redshift drift are derived; the dominant sub-Hubble term is the squared radial velocity gradient, producing a bispectrum that can exceed the squared power spectrum at low z.
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.
Derives the power spectrum evolution and cross-spectra for arbitrary multi-species wave and particle dark matter, incorporating free-streaming, Jeans scales, and intrinsic fluctuations.
The paper calculates multifrequency angular power spectra of the 21 cm line for models with primordial magnetic fields of strength 4 nG and spectral indices -2.9 and -2.5, then estimates signal-to-noise ratios for uGMRT, MeerKAT and SKA1-MID.
Λ_s VCDM is a predictive model combining Λ_s CDM with VCDM gravity via an auxiliary scalar field and sigmoid-smoothed potentials to enable stable mirror AdS-to-dS transitions with possible transient acceleration.
Cobaya is a modular Bayesian analysis code that exploits model interdependencies via automatic caching and a novel parameter-blocking algorithm to minimize sampling cost.
Neglecting linear GR effects biases f_NL at 1–3σ for Euclid/SPHEREx in SFB forecasts; multi-tracer improves Doppler detection and weakly breaks b_ϕ f_NL degeneracy.
Optimal redshift weighting on eBOSS QSO full-shape data reduces uncertainties on H0 by 43.3%, σ8 by 19.7%, w0 by 20.5% and produces a bounded posterior on wa in the CPL model.
HIcosmo is a new JAX-based differentiable framework for background cosmology inference that matches Cobaya results while delivering 8.7x CPU and up to 20x GPU speedups.
A geometric invariance makes the BAO-SN Ω_m gap invariant under sound-horizon rescaling α and requires opposite w(z) deformations for the two datasets, so their combination cannot reach the local H0 value.
iDCDM adds two parameters to LambdaCDM so that dark matter decay produces late-time interacting radiation, yielding a distinctive low-redshift suppression of structure growth while leaving BBN and primary CMB unchanged.
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.
First UVLF-based constraints on model-agnostic isocurvature power spectra for CDM, baryon, neutrino, and dark radiation modes yield consistent 95% credible envelopes over k ~ 0.5-10 Mpc^{-1}.
Planck CMB data set upper limits on vector and axial-vector dark matter-electron couplings for masses 100 eV to 100 keV via energy injection from inelastic scattering and hydrogen absorption.
Develops a short-timescale injection formalism for post-recombination fluctuations, derives CMB impacts from scalar/vector/tensor perturbations, and constrains sequestered dark sector phase transitions to permille-level fractional energy injections.
Model-independent reconstruction shows that early-universe modifications resolving the Hubble tension exist at the background level, requiring a smooth ~15% pre-recombination expansion rate enhancement.
Future global 21-cm observations could beat CMB limits on TeV-scale decaying dark matter for lifetimes ≳10^15 s, especially for decays into neutrinos.
citing papers explorer
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Effective Field Theory of Large Scale Structure and Newtonian Motion Gauges
A Newtonian Motion Gauge found via Einstein-Boltzmann solver maps linear dynamics with scale-dependent growth and GR corrections to Newtonian equations, enabling consistent nonlinear EFT calculations that are transformed back for accuracy in real and redshift space.
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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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CMB Limits on the Absorption of Light Vector and Axial-Vector Dark Matter
Planck CMB data set upper limits on vector and axial-vector dark matter-electron couplings for masses 100 eV to 100 keV via energy injection from inelastic scattering and hydrogen absorption.
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Cosmological constraints on TeV-scale dark matter subcomponents decaying between recombination and reionisation
Future global 21-cm observations could beat CMB limits on TeV-scale decaying dark matter for lifetimes ≳10^15 s, especially for decays into neutrinos.
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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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A unified harmonic framework for dark siren cosmology
The GW-galaxy cross-correlation method, unified with spectral sirens in a harmonic framework, can measure H0 to 1% and Omega_m to 5% precision with 2 years of data from next-generation detectors like Einstein Telescope and Cosmic Explorer.
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Nonlinear Matter Power Spectrum from relativistic $N$-body Simulations: $\Lambda_{\rm s}$CDM versus $\Lambda$CDM
Relativistic N-body simulations of Lambda_s CDM produce a redshift-dependent crest in the matter power spectrum ratio, peaking at 20-25% near the transition and leaving a 15-20% uplift at z=0 on group scales.
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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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Primordial Magnetic Fields at Cosmic Dawn: 21-cm Forecasts with HERA and SKA
Primordial magnetic fields enhance low-mass halo abundance at Cosmic Dawn, advancing Lyman-alpha coupling, X-ray heating and reionization and imprinting detectable signatures on global and fluctuating 21-cm signals observable by HERA and SKA.
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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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What it takes to solve the Hubble tension through Modifications of Cosmological Recombination II: in light of ACT DR6 and DESI DR2
Perturbative modifications to the electron mass m_e(z) resolve the Hubble tension with Planck+ACT CMB data but cannot when DESI DR2 BAO data are added due to lowered Omega_m.
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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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Constraining Cosmological and Astrophysical Parameters with the Cosmic Star Formation History
Cosmic star formation history provides complementary constraints on cosmological parameters, breaking degeneracies when combined with standard probes and yielding H0 = 68.28 ± 0.18 km s^{-1} Mpc^{-1} with DESI data.
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Extended Dark Energy analysis using DESI DR2 BAO measurements
Extended analysis of DESI DR2 data confirms robust evidence for dynamical dark energy with phantom crossing preference, stable under parametric and non-parametric modeling.
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2020 Global reassessment of the neutrino oscillation picture
Updated global fit of neutrino oscillation data gives precise measurements of mixing parameters with a 2.5 sigma preference for normal mass ordering.