A hierarchical Bayesian framework that uses the empirical anti-correlation between AGN variability amplitude and luminosity to infer cosmological parameters from moderate-baseline light curves via importance reweighting.
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Cortˆ es, A
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abstract
The latest results on baryon acoustic oscillations from DESI (Dark Energy Spectroscopic Instrument), when combined with cosmic microwave background and supernova data, show indications of a deviation from a cosmological constant in favour of evolving dark energy. Use of a pivot scale for the equation of state $w$ shows that this evidence is concentrated in the derivative of $w$ rather than its mean offset from $-1$, indicating a new cosmic coincidence where the mean equation of state matches that of the $\Lambda$CDM model precisely in the region probed by the observations. An equivalent way to express this is to say that the dark energy hits the maximum value that it will ever achieve within the observed window. We argue that conclusions on dark energy evolution are strongly driven by the assumed parameter priors and that this coincidence, which we are naming the PhantomX coincidence (where X stands for crossing), may be a signature of this.
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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.
SVD analysis of DESI BAO and SN data identifies the leading measurable direction as Omega_m h^2, with BAO providing tighter constraints than the CMB and tensions localized there across model extensions.
Cosmic variance is modeled as Eulerian bias parameters of a finite-volume realization relative to the ensemble average, disentangling it from galaxy bias in the nonlinear BAO shift.
No CMB-consistent CPL dark energy model can simultaneously fit both the BAOtr and DESI datasets; the 3.7-sigma disagreement at z=0.51 sets an irreducible floor.
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.
A scale-invariant model uses a diluting-matter-dependent potential to connect early and late dark energy via tunneling, alleviating the Hubble tension with best-fit early dark energy fraction ~0.3 at z~5000.
Quintessence models satisfying NEC everywhere predict the w0 > -1 and w0+wa < -1 sector favored by data, due to an approximate degeneracy in the w(z) = w0 + wa z/(1+z) parameterization.
Bin-wise uncorrelated reconstruction from DESI/SDSS BAO and Pantheon+/Union3.1/DES-Dovekie supernovae yields dark energy density peaking then declining and equation of state oscillating with phantom crossing near z~0.7, consistent across datasets at moderate significance.
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.
Reanalysis of DESI full-shape clustering data tightens constraints on neutrino mass, spatial curvature, and dark energy equation-of-state parameters relative to BAO-only results.
DESI BAO+CMB yielding a positive present-day deceleration parameter q0≈0.10 (vs SDSS's q0≈−0.22) is explained by DESI's higher lowest effective redshift (0.295 vs 0.15), not by new physics.
A swampland-inspired DM-EDE coupling is tested against DESI DR2 BAO data, showing the EDE potential construction affects late-time dark energy constraints.
Exponential IR f(T) gravity Model I alleviates Hubble tension but is disfavoured by combined Planck/ACT/SPT+DESI+Pantheon+ data; Model II is ruled out because background constraints force unphysical shifts in CMB parameters.
Extended analysis constrains pseudo-scalar dark energy potentials using expansion history and cosmic birefringence, finding quadratic, linear, and Ratra-Peebles forms viable near GUT scale while axion-like requires large anomaly coefficient.
Upper bounds on total neutrino mass in four phenomenological interacting dark energy models are derived from DESI DR2 BAO plus CMB and SNIa data, showing strong dependence on the interaction term form and statistical preference for models that tighten the bound below the oscillation lower limit.
Interacting k-essence dark energy and non-pressureless dark matter models with two interaction forms are shown to reproduce major cosmological epochs and fit observations comparably to LambdaCDM while admitting late-time de Sitter attractors.
Systematic dataset swaps show DESY5 low-redshift SNIa, Planck CMB plus lensing, and DESI-DR2 BAO as the dominant sources of w0waCDM tension with ΛCDM, while other combinations remain consistent.
Extended 12-parameter fits to Planck PR4, DESI BAO, and Pantheon+/DESY5 supernovae find dynamical dark energy not yet robust, an upper bound on neutrino mass sum of 0.3 eV, reduced lensing anomaly, and persistent Hubble tension at 3.2-3.9 sigma.
This review traces the history of dynamical dark energy, presents the no-go theorem against single-field crossing of w = -1, and surveys viable Quintom constructions including multi-field models and modified gravity in light of DESI DR2 hints.
A review arguing that current DESI/DES data favor Quintom-B dark energy, where the equation of state crosses w=-1 from below to above, with applications to bounces and CMB birefringence.
citing papers explorer
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A hierarchical Bayesian framework for cosmology using Type 1 AGN variability
A hierarchical Bayesian framework that uses the empirical anti-correlation between AGN variability amplitude and luminosity to infer cosmological parameters from moderate-baseline light curves via importance reweighting.
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Data-Driven Discovery of a Simple Phantom-Crossing Dark Energy Parametrization
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.
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Universal distance modes from DESI BAO and Type Ia supernovae: what do cosmological rulers actually measure?
SVD analysis of DESI BAO and SN data identifies the leading measurable direction as Omega_m h^2, with BAO providing tighter constraints than the CMB and tensions localized there across model extensions.
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Cosmic variance or galaxy bias? Disentangling finite-volume and galaxy formation effects in cosmological analysis
Cosmic variance is modeled as Eulerian bias parameters of a finite-volume realization relative to the ensemble average, disentangling it from galaxy bias in the nonlinear BAO shift.
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On the origin of the BAOtr-DESI tension
No CMB-consistent CPL dark energy model can simultaneously fit both the BAOtr and DESI datasets; the 3.7-sigma disagreement at z=0.51 sets an irreducible floor.
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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.
-
Connecting Early Dark Energy to Late Dark Energy by the Diluting Matter Potential
A scale-invariant model uses a diluting-matter-dependent potential to connect early and late dark energy via tunneling, alleviating the Hubble tension with best-fit early dark energy fraction ~0.3 at z~5000.
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Assessing observational constraints on dark energy
Quintessence models satisfying NEC everywhere predict the w0 > -1 and w0+wa < -1 sector favored by data, due to an approximate degeneracy in the w(z) = w0 + wa z/(1+z) parameterization.
-
Reconstructing dark energy with fewer assumptions
Bin-wise uncorrelated reconstruction from DESI/SDSS BAO and Pantheon+/Union3.1/DES-Dovekie supernovae yields dark energy density peaking then declining and equation of state oscillating with phantom crossing near z~0.7, consistent across datasets at moderate significance.
-
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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Reanalyzing DESI DR1: 2. Constraints on Dark Energy, Spatial Curvature, and Neutrino Masses
Reanalysis of DESI full-shape clustering data tightens constraints on neutrino mass, spatial curvature, and dark energy equation-of-state parameters relative to BAO-only results.
-
Present Day Cosmic Acceleration from SDSS and DESI BAO: A Call for Finer Tomography of the DESI Bright Galaxy Survey
DESI BAO+CMB yielding a positive present-day deceleration parameter q0≈0.10 (vs SDSS's q0≈−0.22) is explained by DESI's higher lowest effective redshift (0.295 vs 0.15), not by new physics.
-
Imprint of swampland-inspired coupled early dark energy
A swampland-inspired DM-EDE coupling is tested against DESI DR2 BAO data, showing the EDE potential construction affects late-time dark energy constraints.
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Cosmological Viability of Exponential Infrared $f(T)$ Gravity
Exponential IR f(T) gravity Model I alleviates Hubble tension but is disfavoured by combined Planck/ACT/SPT+DESI+Pantheon+ data; Model II is ruled out because background constraints force unphysical shifts in CMB parameters.
-
On the potential of pseudo-scalar dark energy
Extended analysis constrains pseudo-scalar dark energy potentials using expansion history and cosmic birefringence, finding quadratic, linear, and Ratra-Peebles forms viable near GUT scale while axion-like requires large anomaly coefficient.
-
Neutrino mass constraints in interacting dark energy models after DESI DR2
Upper bounds on total neutrino mass in four phenomenological interacting dark energy models are derived from DESI DR2 BAO plus CMB and SNIa data, showing strong dependence on the interaction term form and statistical preference for models that tighten the bound below the oscillation lower limit.
-
Interacting $k$-essence field with non-pressureless Dark Matter: Cosmological Dynamics and Observational Constraints
Interacting k-essence dark energy and non-pressureless dark matter models with two interaction forms are shown to reproduce major cosmological epochs and fit observations comparably to LambdaCDM while admitting late-time de Sitter attractors.
-
New Insights into Dark Energy from DESI DR2 with CMB and SNIa
Systematic dataset swaps show DESY5 low-redshift SNIa, Planck CMB plus lensing, and DESI-DR2 BAO as the dominant sources of w0waCDM tension with ΛCDM, while other combinations remain consistent.
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Updated Cosmological Constraints in Extended Parameter Space with Planck PR4, DESI Baryon Acoustic Oscillations, and Supernovae: Dynamical Dark Energy, Neutrino Masses, Lensing Anomaly, and the Hubble Tension
Extended 12-parameter fits to Planck PR4, DESI BAO, and Pantheon+/DESY5 supernovae find dynamical dark energy not yet robust, an upper bound on neutrino mass sum of 0.3 eV, reduced lensing anomaly, and persistent Hubble tension at 3.2-3.9 sigma.
-
The Quintom theory of dark energy after DESI DR2
This review traces the history of dynamical dark energy, presents the no-go theorem against single-field crossing of w = -1, and surveys viable Quintom constructions including multi-field models and modified gravity in light of DESI DR2 hints.
-
A short review on Quintom dark energy theory
A review arguing that current DESI/DES data favor Quintom-B dark energy, where the equation of state crosses w=-1 from below to above, with applications to bounces and CMB birefringence.
- Intertwined Constraints in Extended Cosmologies: Dark Energy, Curvature, Neutrinos, and Inflation
- Probing dynamical dark energy with late-time data: Evidence, tensions, and the limits of the $w_0w_a$CDM framework