Trending in Cosmology and Nongalactic Astrophysics
The Bayesian view of DESI DR2: Evidence and tension in a combined analysis with CMB and supernovae across cosmological models
We apply the unimpeded framework to perform a fully Bayesian reanalysis of the DESI DR2 data, using nested sampling with PolyChord to compute evidences for $Λ$CDM and seven extensions across combinations of DESI DR1/DR2, Planck CMB, supernovae (Pantheon+, Union3, DES-SN5YR, DES-Dovekie), and DES-Y1 weak lensing. The Bayesian Ockham's razor penalises extended models, yielding weaker or opposite preferences compared to $Δχ^2$-based analyses. For DESI DR2 BAO combined with Planck CMB alone, the DESI collaboration's $3.1σ$ frequentist preference for $w_0w_a$CDM is eliminated entirely: we obtain ${\ln B = -0.57{\scriptstyle\pm0.26}}$, modestly favouring $Λ$CDM. Adding the corrected DES-Dovekie supernova calibration maintains this concordance (${\ln B = -0.01{\scriptstyle\pm0.27}}$). However, when the original DES-SN5YR calibration is included instead, the DESI collaboration's $4.2σ$ result survives the Bayesian Ockham penalty as a $3.07{\scriptstyle\pm0.10}\,σ$ preference (${\ln B = +3.32{\scriptstyle\pm0.27}}$). That this signal persists despite the Ockham penalty makes the role of tension quantification essential: our analysis traced the preference to the DES-SN5YR calibration error, which introduced a $2.95{\scriptstyle\pm 0.04}\,σ$ conflict with DESI DR2 within $Λ$CDM -- a tension that stands out from the grid -- reduced to $1.96{\scriptstyle\pm 0.04}\,σ$ once the calibration was corrected. With the calibration corrected, the Bayesian evidence for dynamical dark energy vanishes.
2603.05472
Mar 2026Cosmology and Nongalactic Astrophysics
2602.05973Does Cosmology require Hermiticity in Quantum Mechanics?
We explore the consequences of allowing non-Hermitian structures in quantum cosmology by extending the Wheeler DeWitt framework beyond strictly Hermitian dynamics. Using a controlled semiclassical reduction, we show how anti Hermitian contributions propagate into both early universe primordial fluctuations and late-time structure growth as effective damping or gain terms. Confronting this framework with inflationary observables, growth of structure and the observed near flatness of the universe, we derive strong infrared constraints that suppress non Hermiticity across cosmic history. We demonstrate that these bounds are mutually consistent between early and late-time probes and can be partially relaxed in theories beyond General Relativity. Our results establish cosmology as a novel arena for testing foundational aspects of quantum mechanics and suggest that Hermiticity may emerge dynamically along the semiclassical branch describing our universe.
2602.05973
Feb 2026Cosmology and Nongalactic Astrophysics
Fuzzy dark matter soliton core hosting a supermassive black hole as a dense low-mass perturber in strong gravitational lensing
Recent high-resolution imaging observations of strong lens systems reveal dense low-mass perturbers. We propose a soliton core, whose central density is boosted by a supermassive black hole (SMBH), in the fuzzy dark matter (FDM) model as an efficient perturber in strong gravitational lensing. The higher central density makes it less efficient in the tidal mass loss, and leads to the higher impact in gravitational lensing. We show that the mass profile of a $\sim 10^6M_\odot$ perturber in JVAS B1938+666, which does not resemble any known astronomical object, can be wel explained by a soliton core in the FDM model with the mass of $4\times 10^{-21}$eV hosting an SMBH with the mass of $4\times 10^5M_\odot$. The high mass of the SMBH may be explained by several scenarios that predcit heavy SMBH seeds such as the direct collapse black hole formation and primordial black holes.
2601.15718
Jan 2026Cosmology and Nongalactic Astrophysics
Reanalyzing DESI DR1: 4. Percent-Level Cosmological Constraints from Combined Probes and Robust Evidence for the Normal Neutrino Mass Hierarchy
We present cosmological parameters measurements from the full combination of DESI DR1 galaxy clustering data described with large-scale structure effective field theory. By incorporating additional datasets (photometric galaxies and CMB lensing cross-correlations) and extending the bispectrum likelihood to smaller scales using a consistent one-loop theory computation, we achieve substantial gains in constraining power relative to previous analyses. Combining with the latest DESI baryon acoustic oscillation data and using cosmic microwave background (CMB) priors on the power spectrum tilt and baryon density, we obtain tight constraints on the $Λ$CDM model, finding the Hubble constant $H_0=69.08\pm 0.37~\mathrm{km}\,\mathrm{s}^{-1}\mathrm{Mpc}^{-1}$, the matter density fraction $Ω_m=0.2973\pm 0.0050$, and the mass fluctuation amplitude $σ_8 = 0.815\pm 0.016$ (or the lensing parameter $S_8\equivσ_8\sqrt{Ω_m/0.3}=0.811\pm 0.016$), corresponding to $0.6\%$, $1.7\%$, and $2\%$ precision respectively. Adding the Pantheon+ supernova sample (SNe), we find a preference of $2.6σ$ for the $w_0w_a$ dynamical dark energy model from low-redshift data alone, which increases to $2.8σ$ when exchanging the SNe with Planck CMB data. Combining full-shape data with BAO, CMB, and SNe likelihoods, we improve the dark energy figure-of-merit by $18\%$ and bound the sum of the neutrino masses to $M_ν<0.057$ eV in $Λ$CDM and $M_ν<0.095$ eV in the $w_0w_a$ dynamical dark energy model (both at 95\% CL). This represents an improvement of $25\%$ over the background expansion constraints and the strongest bound on neutrino masses in $w_0w_a$CDM to date. Our results suggest that the preference for the normal ordering of neutrino mass states holds regardless of the cosmological background model, and is robust in light of tensions between cosmological datasets.
2601.16165
Jan 2026Cosmology and Nongalactic Astrophysics
Mitigating Simulator Dependence in AI Parameter Inference for the Epoch of Reionization: The Importance of Simulation Diversity
The 21cm signal of neutral hydrogen contains a wealth of information about the poorly constrained era of cosmological history, the Epoch of Reionization (EoR). Recently, AI models trained on EoR simulations have gained significant attention as a powerful and flexible option for inferring parameters from 21cm observations. However, previous works show that AI models trained on data from one simulator fail to generalize to data from another, raising doubts about AI models' ability to accurately infer parameters from observation. We develop a new strategy for training AI models on cosmological simulations based on the principle that increasing the diversity of the training dataset improves model robustness by averaging out spurious and contradictory information. We train AI models on data from different combinations of four simulators, then compare the models' performance when predicting on data from held-out simulators acting as proxies for the real universe. We find that models trained on data from multiple simulators perform better on data from a held-out simulator than models trained on data from a single simulator, indicating that increasing the diversity of the training dataset improves a model's ability to generalize. This result suggests that future EoR parameter inference methods can mitigate simulator-specific bias by incorporating multiple simulation approaches into their analyses.
2601.05229
Jan 2026Cosmology and Nongalactic Astrophysics
Dissecting the Hubble tension: Insights from a diverse set of Sound Horizon-free H0 measurements
The Hubble tension is commonly framed as a discrepancy between local, late-time measurements favoring $H_0 \approx 73$ km s$^{-1}$ Mpc$^{-1}$ and early-time, Sound-Horizon-based measurements favoring $H_0 \approx 67$ km s$^{-1}$ Mpc$^{-1}$. We challenge this viewpoint by analyzing 83 Sound-Horizon-independent $H_0$ measurements, categorized into four classes: Distance Ladder measurements using local calibrators; Local One-Step $Λ$CDM measurements assuming the standard expansion history; Pure Local One-Step measurements independent of $H(z)$ shape; and CMB Sound Horizon free measurements using CMB data without the Sound Horizon scale. We find that the 29 Distance Ladder measurements yield $H_0 = 72.74 \pm 0.40$ km s$^{-1}$ Mpc$^{-1}$ ($χ^2_ν\equiv χ^2/d.o.f= 0.74$), while the 54 One-Step measurements collectively yield $H_0 = 68.67 \pm 0.46$ km s$^{-1}$ Mpc$^{-1}$ ($χ^2_ν= 0.85$), a $6.7σ$ tension exceeding the Planck--SH0ES discrepancy. This tension remains significant at $4.5σ$ after accounting for correlations. Among One-Step categories, Local One-Step $Λ$CDM measurements favor the lowest value ($H_0 = 67.18 \pm 0.90$ km s$^{-1}$ Mpc$^{-1}$), Pure Local One-Step yield an intermediate value ($H_0 = 70.38 \pm 1.00$ km s$^{-1}$ Mpc$^{-1}$), and CMB Sound Horizon Free measurements give $H_0 = 68.71 \pm 0.63$ km s$^{-1}$ Mpc$^{-1}$. Thus, that the Hubble tension is better characterized as a discrepancy between the Distance Ladder and all other methodologies, rather than an early-vs-late-time split. We also identify a $2.4σ$ internal tension among One-Step measurements: analyses assuming $Λ$CDM systematically recover lower $H_0$ values by about 3.2 km s$^{-1}$ Mpc$^{-1}$ compared to model-independent methods. This suggests either unrecognized systematics/physics in the Distance Ladder or deviations from $Λ$CDM in the late-time Universe.
2601.00650
Jan 2026Cosmology and Nongalactic Astrophysics
Dynamical Dark Energy Imprints in the Lyman-Alpha Forest
The nature of dark energy (DE) remains elusive, even though it constitutes the dominant energy-density component of the Universe and drives the late-time acceleration of cosmic expansion. By combining measurements of the expansion history from baryon acoustic oscillations, supernova surveys, and cosmic microwave background data, the Dark Energy Spectroscopic Instrument (DESI) Collaboration has inferred that the DE equation of state may evolve over time. The profound implications of a time-variable, ``dynamical" DE (DDE) that departs from a cosmological constant motivate the need for independent observational tests. In this work, we use cosmological hydrodynamical simulations of structure formation to investigate how DDE affects the properties of the Lyman-Alpha ``forest'' of absorption features produced by neutral hydrogen in the cosmic web. We find that DDE models consistent with the DESI constraints induce a spectral tilt in the forest transmitted flux power spectrum, imprinting a scale- and redshift-dependent signature relative to standard Lambda-CDM cosmologies. These models also yield higher intergalactic medium temperatures and reduced Lyman-Alpha opacity compared to Lambda-CDM. We discuss the observational implications of these trends as potential avenues for independent confirmation of DDE.
2601.00767
Jan 2026Cosmology and Nongalactic Astrophysics
One-loop power spectrum corrections in interacting dark energy cosmologies
Interacting Dark Energy (IDE) models offer a promising avenue to explore possible exchanges of energy and momentum between dark matter and dark energy, providing a dynamical extension of the standard $Λ$CDM paradigm. Such interactions modify the growth of cosmic structures, imprinting distinctive signatures on the matter power spectrum that can be tested through large-scale structure (LSS) observations. In this work, we compute the one-loop corrections to the matter power spectrum in IDE models. We then reinterpret these results within the standard framework of the Effective Field Theory of Large-Scale Structure (EFTofLSS), which provides a consistent description of mildly non-linear scales and allows for reliable comparisons with observational data. We investigate two commonly studied forms of the coupling function, $Q$, namely $Q = ξ\mathcal{H} ρ_{\rm m}$ and $Q = ξ\mathcal{H} ρ_{\rm DE}$, and introduce a novel interaction term, $Q = Γ\, ρ_{\rm m} \, ρ_{\rm DE} \, θ_{\rm m}$, characterized by the non-linear coupling constant $Γ$, which links the interaction strength to the velocity divergence of dark matter. This coupling function is proposed to isolate the effects solely of the IDE model on mildly non-linear scales. Using Full-Shape (FS) measurements of the galaxy power spectrum from BOSS DR12, we constrain the interaction rate $Γ$, the cosmological parameters, and the bias parameters. We find $Γ= 0.0039 \pm 0.0082$, which is highly consistent with the $Λ$CDM model. This work opens the possibility of testing IDE models at mildly non-linear scales, potentially providing new insights for this class of models beyond the standard $Λ$CDM framework.
2512.11678
Dec 2025Cosmology and Nongalactic Astrophysics
