claims depot shelf
Dark Energy
Formal claims (Lean)
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On the paper's own terms, the central discovery is that the field equations of phantom scalar-field cosmologies with dark-matter interactions allow a normalization $D = \sqrt{\tfrac12\dot{\phi}^2 + V + \rho_m}$ such that the dimensionless state variables $\chi$, $\zeta$, $\xi$ lie on the unit sphere and the first Friedmann constraint closes the system, giving a compact two-dimensional phase space
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The central claim is that a dust sphere of mass $M$ initially at rest in a spacetime with cosmological constant $\Lambda$ can collapse only if its radius satisfies $b_0 \le (3 r_g/(2\Lambda))^{1/3}$, which becomes $b_0 \le (GM/H^2)^{1/3}$ after substituting $\Lambda = 3H^2$. The derivation works from the Tolman metric, which yields an evolution equation for the boundary radius, $\dot b^2 = f(R_0)
Stated claims
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The central discovery is that axion isocurvature is not merely a CDM analogue but a mass-dependent CMB observable with three regimes. For $m_a \gg H_{\rm eq}$ the axion isocurvature transfer function is indistinguishable from CDM isocurvature, so Planck's $\beta_{\rm iso} < 0.038$ bound applies directly and yields the $r f_{\rm dm}$ inequality of Eq. (22). For $H_0 \ll m_a \lesssim H_{\rm eq}$, Jeans suppression cuts off the spectrum with a $\sim(\ell_J/\ell)^6$ falloff, breaking the degeneracy with CDM and leaving unique scale-dependent signatures, but also making the inflationary signal undetectable even under optimistic cosmic-variance-limited forecasts. For $m_a \lesssim H_0$, the axion behaves as dark energy and the isocurvature signal peaks at the quadrupole, scaling as $(m_a/H_0)^2$; a detection there would contradict the standard inflationary production mechanism. The paper's quantitative claim is that the crossover where isocurvature constraints beat tensor constraints occurs at $m_a f_{\rm dm}^2 \gtrsim 10^{-26.4}\,{\rm eV}$, with an open coexistence window near $10^{-25}\,{\rm eV}$.
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The central discovery is that the level of evidence for dynamical dark energy, measured by fitting the CPL parametrization $w(a)=w_0+w_a(1-a)$ to BAO and uncalibrated supernova data, is not a single number but a field over the early-universe parameters ($H_0 r_d,\Omega_m$). Only the product $H_0 r_d$ and the expansion shape $E(z)$ are accessible to these late-time probes, so the same data can support 'cosmological constant' or 'dynamical dark energy' depending on where the early universe places the model. The CMB angular scale provides an almost model-independent ridge in this plane, and the minimum of the dynamical-dark-energy preference, the 'nexus,' sits on that ridge without having used CMB data. Early-universe solutions to the Hubble tension, which move the joint fit to higher $H_0 r_d$ and lower $\Omega_m$, push the fit toward that nexus and reduce the significance from about 2.5σ to 1.3σ, making the apparent preference depend on the assumed early cosmology. A fourth-order Chebyshev reconstruction of the dark energy density confirms the same weakening near the nexus.
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GCT modifies gravity from the fluid side by coupling a vector field $S_\mu$ to the standard energy-momentum tensor through a source term proportional to $(\partial w_f)^2$, where $w_f$ is the total fluid equation of state. In the radiation- and matter-dominated eras this source vanishes and the field decays to a stable critical point, while during the radiation-matter transition it drives a transient EDE component whose peak occurs near equality. The same field admits Λ-cancelling solutions that asymptote to a linearly expanding universe, and, through a critical point at infinity, an Early Static Hot Universe in which the field offsets hot gas so that a large comoving Hubble radius is generated. A Minkowski-space perturbation analysis singles out $c_2 = 1$ for stability, recovers the Newtonian limit with $\gamma_{\rm PPN}=1$ under asymptotically flat boundary conditions, and yields six gravitational-wave polarizations propagating at the speed of light.
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The central claim is that the dark energy driving late-time acceleration can be an emergent geometric component rather than a cosmological constant or a phenomenological parametrization. In the CKG framework the divergence-free conformal Killing tensor of the Robertson–Walker spacetime behaves as a perfect fluid with density $\mu_D = -\frac{1}{2} C a^2 + \Lambda$ and pressure $p_D = \frac{5}{6} C a^2 - \Lambda$, which contributes to the Friedmann equation only as $\Omega_D/(1+z)^2$. With $\Omega_D < 0$, the effective equation of state $w_D(z) = -1 - \frac{2}{3}\frac{\Omega_D}{\Omega_D + \Omega_\Lambda(1+z)^2}$ is above $-1$ at late times and approaches $-1$ at high redshift, so the expansion history differs from ΛCDM only after recombination and never crosses the phantom divide. The fits yield $\Omega_D$ negative (bounded below by $-0.0413$ for CMB+DESI DR2 alone, with means around $-0.04$ to $-0.07$ when supernovae are added), an unchanged sound horizon of about $147.8$ Mpc, a future critical redshift $z_c \approx -0.7$ to $-0.8$ at which $H(z_c)=0$, and log Bayes factors of $-5.5$ to $-6.8$ favoring CKG.
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On the fixed RN–AdS–Kiselev geometry, with a negatively charged test particle in a monotone electrostatic potential $\Psi(r)$, the paper establishes three claims. The generalized electrostatic ergosphere defined by $|q|\Psi(r_E)=\sqrt{f(r_E)}$ has a unique exterior boundary, and this boundary moves outward with increasing charge magnitude, mass, black-hole charge, quintessence amplitude, and more negative state parameter. Any negative-energy trajectory has a unique turning point and then moves monotonically inward to the horizon, so the infalling fragment cannot return. The energy of the escaping fragment is locally bounded by $E_{2,\max}=E_0+|q_1|\Psi(r_*)-\sqrt{f(r_*)}$, with efficiency ceiling $\eta_{\max}=(|q_1|\Psi(r_*)-\sqrt{f(r_*)})/E_0$, and combining this with a finite-radius reception inequality gives a sufficient condition for extraction to a detector at radius $R_{\rm obs}$. The paper also presents first-order adiabatic laws showing that, under slow Maxwell discharge at fixed mass, the horizon moves outward while the electrostatic boundary stays nearly stationary, so the negative-energy layer thins; with simultaneous accretion both surfaces move outward.
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The paper's central claim is that isotropic cosmic birefringence, $\beta\approx0.3^\circ$, can be produced by a 3-form dark-energy field through the parity-violating interaction $\mathcal{L}_{\mathrm{int}}=\epsilon\lambda\,C_{\mu\nu\rho}F^{\mu\nu}A^{\rho}$. In a homogeneous isotropic background the 3-form reduces to a single function $\chi(t)$, with $C_{ijk}=a^3\chi\,\epsilon_{ijk}$, and the interaction shifts the two photon helicity dispersion relations oppositely, giving $\beta=-(\epsilon\lambda/2)\int dt\,\chi$. With $\lambda\sim m_\gamma/M_p$ from a smooth decoupling limit of the Stückelberg completion, this becomes $\beta\sim(m_\gamma/H_0)\,I$, where $I$ is an order-unity phase-space integral, so matching $\beta\approx0.3^\circ$ requires $m_\gamma$ within a few orders of magnitude of $H_0$. The dimension-6 gauge-invariant operator $G_{\mu\nu\rho\sigma}F^{\mu\nu}F^{\rho\sigma}$ instead requires an effective coupling $\Lambda^{-2}$ of order $10^{20}\,\mathrm{GeV}^{-2}$ or larger, which the authors argue is incompatible with effective field theory. The paper also derives potential-independent universal profiles $\beta(z)$ for the dimension-4 operator: the small-field branch matches the axion-like-particle dark-energy profile, while the large-field branch damps at low redshift, with middle-field initial conditions interpolating between them.
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The central claim, stated on the paper's own terms, is that the gravitational-wave background generated at the inflation–kination transition constrains the post-inflationary field excursion enough to decide the viability of quintessential inflation. Concretely, the GW abundance fixes a minimum radiation fraction at the onset of kination, $\rho_{r,\mathrm{kin}} \ge 100\,\rho_{\mathrm{GW,kin}}$, which becomes a lower limit on $T_{\mathrm{RH}}$ and an upper limit on the excursion $\Delta\varphi \simeq \sqrt{6}\,M_{\mathrm{Pl}}(N_{\mathrm{RH}}+\ln 2)$. The potential must drop by $D_{\mathrm{req}} = \ln[\tilde V(\varphi_{\mathrm{kin}})/\rho_{\Lambda,0}] \sim 216$–$242$ over this excursion, so the average logarithmic slope must be $\bar\lambda = D_{\mathrm{req}}M_{\mathrm{Pl}}/\Delta\varphi$. For the single-exponential coupling the local slope is constant, $\lambda_0 = 2M_{\mathrm{Pl}}/f_0$, so the matching condition $\bar\lambda \simeq \lambda_0$ forces $f_0 \lesssim 0.3\,M_{\mathrm{Pl}}$, meaning $\lambda_0^2 \gtrsim 44$; the standard attractor analysis of exponential quintessence then places the field unavoidably on the matter-scaling solution with $w_\varphi \to 0$ and $\Omega_\varphi \to 3/\lambda_0^2 \lesssim 0.07$. The double-exponential coupling $K = e^{-\phi/f_0} + A\,e^{-\phi/f_1}$ leaves the average slope steep while the shallower exponential softens the asymptotic slope to $\lambda_1 = 0.7$ near freezing, and the full numerical evolution from inflation to the present epoch yields thawing quintessence with $w_{\varphi,0} \simeq (-0.90,-0.95)$, a deviation from $-1$ large enough for current and forthcoming dark-energy surveys to see.
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The central claim is that a two-axion dark sector with a light dark-energy axion and a heavy dark-matter axion can be recast exactly as coupled quintessence, provided the heavy axion stays on its WKB branch. The interaction endows the dark-matter mass with a phi dependence given by $m_\chi(\phi) = m_\chi \sqrt{1 + \beta \cos(\phi/f_\phi)}$, Eq. (11), so the dark-matter density follows $\rho_\chi/\rho_{\chi,0} = (m_\chi(\phi)/m_{\chi,0}) a^{-3}$, Eq. (18). Because the effective potential for $\phi$ shifts its minimum from $\phi = \pi$ at early times to $\phi = 0$ at late times, the field's derivative changes sign; the coupling $Q(\phi)$ consequently switches from negative to positive, injecting energy into the dark-matter component and producing a percent-level dip in $\rho_\chi$ relative to cold dark matter. When this is interpreted as a standard dark-energy component plus standard CDM, the resulting effective equation of state, Eq. (38), crosses below $w = -1$ at low redshift although the actual field equation of state stays above $-1$. This offers a string-motivated, non-phantom explanation of the DESI DR2 preference for an apparent phantom crossing.
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The central claim, stated in the abstract and conclusions, is that for the five dark energy parameterizations the present-day growth index and its first derivative are compatible with previously reported ranges, and the combination parameter A(z) is lower than the LambdaCDM value for all five models and all three supernova compilations, while statefinder diagnostics differ from LambdaCDM. If correct, these are real phenomenological signatures of slowing cosmic acceleration that future redshift-space distortion and weak lensing measurements could in principle distinguish.
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The central discovery is a joint dark-sector degeneracy: late-time BAO and supernova distances prefer $w_{\mathrm{DE}}>-1$, while the CMB fixes the early-Universe matter density around last scattering; a positive $w_{\mathrm{DM}}$ changes how that early density maps to the present, lowering the dark-matter density at $z=2.33$ and increasing the matter-era distance interval by about 0.2%, which relieves a tension with the high-redshift acoustic scale. In the constant-$w$ extension this yields $w_{\mathrm{DM}}\sim0.001$ and $w_{\mathrm{DE}}\sim-0.94$, with both standard values outside the 95% contour, while releasing only one parameter at a time gives no comparable departure. With dynamical dark energy, allowing phantom crossing absorbs this geometric freedom and makes $w_{\mathrm{DM}}=0$ consistent; when phantom crossing is forbidden, the positive $w_{\mathrm{DM}}$ preference returns. A non-phantom Pad\'e-$w$+$w_{\mathrm{DM}}$ model is mildly preferred over the phantom-crossing $w_0w_a$ model by best-fit $\chi^2$ and DIC, leading the authors to conclude that the apparent phantom-crossing preference may instead reflect deviations in the dark-matter sector.
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The central claim is that, with DESI BAO DR2, Pantheon+, and compressed Planck 2018 CMB distance priors, the $w_0w_a$CDM model is not favored over $\Lambda$CDM. In every redshift-cut fit, $\Lambda$CDM ($w_0=-1$, $w_a=0$) remains inside the 95% confidence region. The largest deviation, about $2\sigma$, occurs when BAO and SNe Ia in $z\sim0.4$--$0.8$ are included, coinciding with the DESI LRG1 and LRG2 samples; excluding or adding higher-redshift data weakens the shift. AIC values give $|\Delta\mathrm{AIC}|<1$ in the most relevant cuts and at most weak evidence elsewhere, while BIC consistently penalizes the extra parameters of $w_0w_a$CDM. A parameter-shift consistency test between complementary subsamples finds no significant tension, with the smallest probability-to-exceed at $z_{\rm cut}=0.8$ being $\mathrm{PTE}=0.062$.
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On its own terms, the paper's central claim is that the analytically tractable Extended Cuscuton sector provides a controlled, minimally modified dark-energy target that remains close to $\Lambda$CDM but is not observationally inert. The four benchmark submodels defined by the sign of $\tilde c_1$ and by the two asymptotic de Sitter branches all fit the combined CC+BAO+SN data with $\Omega_\Lambda = 0.73 \pm 0.01$ and $H_0 \simeq 71.7$ km s$^{-1}$ Mpc$^{-1}$, with the model dependence absorbed entirely by the shape parameters $\tilde c_2$ and $\tilde c_4$; none of the models removes the $H_0$ offset between the supernova-calibrated and BAO-calibrated combinations (about 72.5 versus 69.2 km s$^{-1}$ Mpc$^{-1}$). The forecast claim is that third-generation bright-siren networks, especially the kilonova channel with two Cosmic Explorer detectors added to Einstein Telescope, can recover the fiducial $\Lambda$CDM cosmology within the enlarged parameter space and measure $H_0$ with relative uncertainty as low as 0.21% and $\Omega_\Lambda$ at the 1.87% level, with all configurations staying below 13.18% on $H_0$. The paper concludes that standard sirens at third generation can provide a precise complementary probe of non-dynamical dark energy beyond $\Lambda$CDM.
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The central discovery is that a specific interacting dark-sector theory—a quintessence field coupled to dark matter by the conformal transformation g̃μν = e^{-2αφ}gμν, with a potential engineered so ρφ = Λ + ρDM - ρc—can simultaneously keep the ΛCDM background and lower late-time structure growth enough to reconcile early-universe CMB measurements with growth data. In the fit, the conformal coupling drains energy from dark matter into the field, reducing the matter density at low redshifts and suppressing clustering, yielding σ8,0 ≈ 0.762 ± 0.010 and Ωm,0 ≈ 0.311 ± 0.007. The same analysis shows that adding a disformal coupling D_m^4 e^{-2(α+β)φ}∂μφ∂νφ acts as friction that damps this exchan
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The paper establishes a reliable operating point for Augur: normalized derivative step size of 5% of the uniform prior range for every parameter, evaluated with the 5-point stencil or numdifftools, and n(z) represented by roughly 500 spline knots. At this point the Fisher matrix approximates the local likelihood well enough that its full correlation matrix sits within 0.05 of the nested-sampling correlation matrix for both Y1 and Y10 setups, its w0-wa degeneracy direction matches sampling, and its Dark Energy Figure of Merit agrees with the DESC SRD pipeline to 10% (Y1) and 2% (Y10). The paper also characterizes unstable regimes: at smaller step sizes, oscillatory features in non-linear matt
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The central claim is that the observed gravitational-wave strain from a compact binary merger contains two separable cosmological observables: the luminosity distance dL from the oscillatory part of the signal, and the integrated cosmological memory (ICM) offset from the post-merger step. The ICM amplitude follows N+ = h⊕/(3 E^{2/3}(z0)) ∫0^{z0} (1+z)/E^{4/3}(z) dz, where E(z)=H(z)/H0; because this integral weights the expansion history differently than dL does, the pair (dL, R=N+/h⊕) lands on a unique point in the R–dL plane for each expansion history, fixing both distance and redshift for a single event. The authors demonstrate the extraction in simulation: standard Bayesian parameter esti
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The paper's central discovery is a replication: taking the numbers (264°, 48°) from the criticized analysis and treating them as equatorial right ascension and declination exactly reproduces the reported hemisphere split of 724/840 supernovae in the N=1564 Pantheon+ sample, whereas the CMB dipole direction properly converted from Galactic to ICRS coordinates, (167.8°, -7.1°), yields 539/1025. This shows the criticized analysis computed cosθ with a reference direction that was not the CMB dipole at all, because the supernova positions in Pantheon+ are given in equatorial coordinates, so the reference direction must also be equatorial.
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The central assertion is that an exactly FLRW background can coexist with a matter sector that has a preferred spatial direction, because isotropy is realized only on shell. For a vector-field Lagrangian of the form (2.4), the conditions (2.8) cancel the anisotropic stress for arbitrary homogeneous configurations, and the temporal vector equations (together with an off-shell identity from Ref. [32]) make the momentum density vanish. The paper shows that the resulting background cosmology looks identical to an isotropic dark sector, while the same hidden direction controls perturbation effects: direction-dependent GW propagation and a linear mixing term (4.4) between a scalar-type vector pert
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The paper claims that linear matter clustering at scales near k=0.1 h/Mpc is plausibly suppressed relative to the GR/ΛCDM prediction, with an effective gravitational coupling Geff=G/(1+Aξ) where ξ∝(1+z)/k². Using a joint MCMC analysis of 35 uncorrelated fσ8 measurements, cosmic chronometer H(z) data, Pantheon+ supernovae, and CMB power spectra and lensing, the inferred amplitude A=4425±2000 (equivalently B=0.36+0.14−0.12) gives a 2.2σ preference for a non-zero scale-dependent term. The suppression is stronger during the matter-dominated era than in the dark-energy-dominated epoch, and the derived S8=0.831±0.011 matches the CMB-inferred value without exacerbating either the S8 or H0 tensions.
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The paper establishes that a constant 'radioactive' decay rate Γ for dark energy, measured in units of the Hubble rate H0, is compatible with the full current data set. For distance data alone (DESI DR2 BAO plus supernovae), the posterior for Γ/H0 shifts positive by about 2σ, corresponding to a dark-energy density that decreases with time and an effective equation of state w > -1 at low redshift. Adding CMB data from Planck or Planck+ACT removes this preference, making Γ/H0 consistent with the ΛCDM value of zero. The DESI DR1 full-shape analysis, which is new for these models, breaks the degeneracy between decay channels: decaying into dark matter changes the matter abundance and perturbatio
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The paper's central claim is that the density-level pivot construction applied to CPL removes the parameter correlation that made the standard $(\omega_0,\omega_a)$ basis look degenerate, and that in this physically motivated basis $\omega_0\omega_a$CDM remains favored over $f_af_b$CDM and reproduces quintessence backgrounds more accurately. The transformation is exact: $(\omega_0,\omega_a)\leftrightarrow(\omega_p,f_p)$ leaves the expansion history and likelihood unchanged, so any statistical difference comes from the coordinate system. For CPL, the optimized pivot scale factor is $a_p\simeq0.76$, giving $\mathrm{corr}(\omega_p,f_p)\simeq0$; for $f_af_b$CDM, the same procedure leaves a resid
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On the paper's own terms, the discovery is that after subtracting a redshift-dependent magnitude offset of the form Δμ = 0.183(1 − e^{−2.2z}) from each distance modulus, the corrected Pantheon+ and DES-SN5YR Hubble diagrams are described almost exactly by the closed form d_L = (c/H0)(1+z)ln(1+z). Fitting only H0 per survey gives lower χ² than a two-parameter flat ΛCDM model; an extended quadratic term in ln(1+z) is consistent with zero; and the wCDM confidence contours pass through the corresponding point (Ω_DE = 1, w = −1/3). The same conclusion emerges from a model-independent construction of the kernel K = (H0/c) d[d_L/(1+z)]/d ln(1+z), which is consistent with the logarithmic prediction
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On the paper's own terms, the central discovery is a reframing: the 'Hubble tension' between local distance measurements and the CMB is not primarily a conflict over the expansion rate H0 but a conflict over the standardized peak absolute magnitude M_B of Type Ia supernovae. The first two rungs of the distance ladder measure M_B = -19.204 ± 0.030 from 17 nearby Cepheid-calibrated host galaxies, with no cosmological assumption. The same supernova population, inserted into CMB-constrained standard cosmology and fit over redshifts 0.04 to 1, demands M_B = -19.430 ± 0.013. The 0.23-magnitude gap is about 7 sigma and survives any smooth change in the late-time expansion history; fitting the magni
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For the parameters Ωm, Ωb, w0, and wa, the combination of WL peak statistics provides a tighter constraint than the shear two-point correlation functions ξ±, with the redshift distribution of SNR>3 peaks being the most powerful individual statistic—driving the Ωm, w0, and wa constraints and breaking degeneracies that let the combination also probe Ωb and h. The height distribution and angular clustering are most sensitive to the amplitude of the primordial power spectrum, ln(10^10 A_s). Combining the three statistics also breaks degeneracies that no single statistic can resolve on its own, and the paper finds that smaller smoothing scales typically yield better constraints, with the figure o
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On the paper's own terms, the central discovery is that the DESI BAO evidence for w0waCDM carries an anytime-valid false-positive guarantee only under the right test specification, and that the signal is localised almost entirely in one redshift bin. The running mixture e-value M_DR2 = 33.97 crosses the illustrative 5% threshold of 20, giving a Markov p-value of 0.029, but this rejection requires a narrow prior concentrated near the DR2-preferred direction and a signal shared coherently across the bins. Leave-one-out analysis shows LRG2 carries 78.6% of the summed evidence; recomputing on the remaining six bins gives M = 0.49, mildly favouring the cosmological constant. Allowing each of the
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On the paper's own terms, the central discovery is that the cosmological relic state can spontaneously break the exact Z_N symmetry of the Lagrangian, storing the initial axion value in the WIMP sector. Freeze-out with slow inter-sector conversion produces Boltzmann-suppressed relic fractions that retain a memory of the initial axion angle, generating an unsuppressed finite-density potential V_fd ≈ σ_fd n_χ [1 - cos(Θ - Θ_i)]. This potential traps the axion at Θ_i at early times; once n_χ drops below Λ_D/σ_fd, the vacuum potential releases it, and the relic-weighted WIMP mass increases, transferring energy from DE to DM. The result is an effective equation of state that crosses below -1, com
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In the joint CMB-SPA + DESI BAO + full-shape analysis, allowing free spatial curvature yields Ωk = (3.0 ± 1.1) × 10^{-3} and ns = 0.9692 ± 0.0035. This value is 1.8σ lower than the flat-ΛCDM result and brings Starobinsky and Higgs inflation back inside 2.3σ and 1.5σ, respectively. The same data therefore favor a slightly open universe at 2.7σ, and the apparent conflict with plateau inflation is an artifact of the flat-ΛCDM prior rather than a robust exclusion.
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For the representative KGB model they simulate, braiding enhances dark-energy clustering, raises the Weyl-potential amplitude, and slows its time evolution. That produces up to roughly 12% more weak-lensing convergence power than k-essence at multipoles around 100–1000, while the ISW–RS signal is suppressed by tens of percent in the linear regime and then overtakes k-essence once nonlinear evolution dominates—differences that linear Boltzmann codes miss at those scales.
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The authors establish, using analytic arguments, that a mass-varying dark matter model with one bare potential V(φ) and one coupling scale M can generate an early dark-energy-like peak near matter-radiation equality and a late-time apparent phantom crossing near matter-dark-energy equality. The early peak's amplitude is set by the ratio m(φi)/m(φ0) − 1, its timing by the curvature of m(φ), and the late-time crossing is driven by the bare potential pushing the field at low redshift—exponential potentials doing this most naturally. Since both effects stem from the same mass function m(φ), the same range of M controls both, and the timing tracks the background evolution rather than separate ene
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The central claim is that the anisotropy of Lyman-alpha correlations at z_eff=2.33 carries an Alcock-Paczyński signal that can be measured from the broadband, smooth part of the correlation function rather than only from the BAO peak. Combining the Lyman-alpha auto-correlation and the Lyman-alpha-quasar cross-correlation, the paper measures the broadband AP parameter phi_s = 1.007±0.011, corresponding to D_M/D_H = 4.578±0.052; adding the BAO-peak AP constraint gives a full-shape result D_M/D_H = 4.572±0.046, a 1.0% measurement. The joint full-shape and BAO fit gives D_M/r_d = 39.32±0.33 and D_H/r_d = 8.600±0.066 at z_eff=2.33. The paper argues that systematics from small-scale non-linearitie
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Within the Swampland framework, the paper's central claim is that invoking an ultralight axion to explain the suggested CMB polarization rotation ϑ ∼ 10^-3 radians is in genuine tension with the magnetic Weak Gravity Conjecture bound Λ³_QCD ≲ m f M_Pl. For decay constants f ∼ 10^11–10^16 GeV this bound forces m ≳ 10^-28–10^-23 eV, right next to the mass range m ≲ 10^-28 eV that the birefringence signal requires. The same rotation, however, can be produced by vacuum interfaces: thin axionic domain walls with residual electromagnetic Chern–Simons couplings twist photon polarizations by a discrete Pancharatnam phase. Under minimal assumptions, the accumulated twist along any line of sight equal
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Once reconstructed with f(Q,T)=αQ^m+βT and a hybrid scale factor, the model produces a nonsingular asymmetric bounce near t≃−0.09, where the Hubble parameter flips from negative to positive, then evolves so the effective equation of state approaches −1 at the present age, while energy conditions behave as required for a bounce followed by late acceleration.
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Starting from the luminal Horndeski action with G2 = a1 X + a2 X^2 - V(phi), G3 = 3 a3 X box phi, and a constant Planck mass, plus the covariant interaction beta Z^2 with Z = u_c^mu grad_mu phi, the paper shows that the background evolves from w_DE ~ 1/6 in the radiation era to a stable phantom phase with w_DE < -1 at intermediate redshifts, then returns to w_DE > -1 at z_c ~ 0.36-0.66 as the exponential potential grows. The same interaction that leaves the CDM background untouched introduces a velocity inertia q_c > 1, which in the quasi-static regime drives the effective CDM gravitational coupling below G despite the braiding enhancement of the baryonic coupling. Around radiation-matter eq
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The paper's central claim is that, in a self-consistent Bayesian analysis that deliberately excludes large-scale CMB polarization data, robust astrophysical probes of the reionization history—quasar damping wing observations and dark pixel constraints—combined with a physically motivated Gompertzian reionization model recover an optical depth τreio = 0.067 ± 0.011 (68% CL) under a w0waCDM cosmology. This value agrees with the τ ≈ 0.06 inferred from analyses that do include large-scale CMB polarization, and it contradicts the inflated values (~0.09) that had been used to suggest the dark-energy preference is a polarization artifact. The dynamical dark energy scenario still fits the data bette
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On the paper's own terms, the discovery is that late-time cosmology can accommodate an oscillatory interaction between matter and an effective vacuum component without disturbing the standard expansion history. The model posits ρ_BR(z) = A_BR ρ_m0 cos(f_BR z)(1+z)^3 with p_BR = −ρ_BR, so the matter-like sector no longer scales purely as (1+z)^3; the exact solution for the Hubble rate involves sine and cosine integral functions. Fitting CMB, BAO, and supernova data, the authors find |A_BR| ≤ 0.1 at one sigma in every configuration tested, A_BR consistent with zero, f_BR essentially unconstrained, and no significant shift in H0, Ωm, or σ8. They interpret the full-data ΔDIC = −2.5 with free f_B
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The central claim is that in the ΛXCDM model the effective equation of state of the composite dark-energy fluid, w_eff = −1 + (1+w_X) Ω_X/Ω_D, necessarily crosses the phantom divide from phantom-like to quintessence-like behavior as Ω_X changes sign, provided the cosmon X behaves as phantom matter (w_X < −1, Ω_X < 0 today) and the vacuum runs with coefficient ν < 0 (equivalently ϵ = ν(1+w_X) > 0). The crossing redshift is given by an explicit formula, and when the model is fitted to Planck PR4 CMB data, DESI DR2 BAO data, and either Pantheon+ or DES-Dovekie supernovae, it yields z* ≈ 0.2–0.9 at 95% CL, consistent with the crossing inferred from model-agnostic analyses of the same data. In th
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The authors integrate the GREA background directly into a Boltzmann solver and evolve the entropic component as an effective dark-energy fluid with sound speed c_s² = 1, regulated by the parametrized-post-Friedmann scheme so perturbations remain regular through the phantom crossing. The resulting angular power spectra and growth functions are new. When fit to the CMB-SPA (Planck+ACT+SPT) likelihood, DESI DR2 BAO, and Pantheon+/DES Dovekie supernovae, the inferred coupling α—the ratio of spatial-curvature scale to the causal horizon today—clusters tightly around unity (α≈1.00–1.08 for the CMB-anchored combinations), in agreement with the model's parameter-free prediction. The fit is statistic
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On its own terms, the paper establishes that the GEDE extension is not favored by current data. For the CMB+DESI DR2 combination alone, the preferred Δ is 0.46±0.25, about 1.8σ from ΛCDM; adding any of the three supernova samples pulls Δ to within 0.06–0.33σ of zero. The Hubble constant comes out at 67.9–69.8 km/s/Mpc, the sound horizon at 147.4–147.6 Mpc, and S8 at about 0.821, all consistent with ΛCDM. The equation-of-state parameter w(z) never crosses -1; it stays phantom-like or quintessence-like depending on the dataset, and with Pantheon+ it approaches w≈-1. The authors read this as evidence that the dynamical dark energy suggested by DESI DR2 is not of the generalized emergent form, a
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The central claim is that the entropy-area relation with a scale-dependent exponent Δ(x)=Δ0+Δ1/ln x, where x=(H1/H)^2, when fed into the gravity-thermodynamics first law on the apparent horizon, yields an exact analytic Hubble rate H(z). Combined fits to Hubble-rate measurements, type Ia supernova distances, baryon acoustic oscillations, and CMB shift parameters give H0 = 69.27^+0.62_-0.65 km/s/Mpc with Δ0 ≈ 2.4×10^-3 and Δ1 ≈ -0.65, implying Δ(0) ≈ 1.09×10^-4. The derived Δ(z) crosses zero at z_tr ≈ 100 (with broad uncertainties), connecting a negative-Δ early phase to a positive-Δ late phase. The model is fully consistent with the data but is not statistically preferred over ΛCDM (ΔBIC ≈ 7
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The central discovery is that a cosmological model in which the Gauss-Bonnet correction to the Wald entropy of the apparent horizon is sourced by the astrophysical history of black-hole formation and mergers fits the combined early- and late-Universe data better than ΛCDM, with the coupling parameter Cn = 0.435^{+0.150}_{-0.132}, a ~3σ phantom-side deviation from zero. The mechanism preserves the standard acoustic scale, leaving the primary CMB nearly unchanged, while the late-time expansion is enhanced enough to shift H0 upward by about 1.3 km/s/Mpc. The cost is a modest rise in S8, and independent growth probes (lensing and redshift-space distortions) are slightly worse-fit than in ΛCDM. T
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On the kinematic branch HL = 1, for any barotropic background with w_b > -1 and any entropy modification whose local logarithmic slope satisfies chi_cr < 2, the phantom-divide crossing is unique inside the physical phase space 0 < Omega_X < 1, occurs at a strict local maximum of the event-horizon radius, proceeds from quintessence into phantom, and yields the exact local entropy-scaling dimension d_S,cr = 4 + 3 w'_X,cr / (1 + q_cr) expressed solely in kinematic quantities.
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By consolidating the normal and self-accelerating DGP branches, cubic scalar and vector Galileons, the generalised cubic covariant Galileon and generic EFT parameterisations into a single master Vainshtein equation whose physics is carried by three time-dependent background functions, EFT-RAMSES produces nonlinear matter power spectra that agree with both its parent code and an independent approximate code while correctly recovering Vainshtein screening.
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Two robust paths exist to a cosmic ∑mν bound that does not hinge on the late-time dark-energy model. Full-data marginalization over (w0, wa) already captures the dark-energy directions that affect ∑mν: the bound saturates at ∑mν < 0.152 eV under binned and cubic w(a) as well. Separately, a late-Universe-free combination—primary CMB with Alens free plus the four-point reconstructed lensing spectrum C_L^{κκ}—removes late-time expansion dependence by construction and gives ∑mν < 0.41 eV today, stable to a few percent across ΛCDM, wCDM, (w0, wa), and more flexible smooth histories, tightening toward ~0.31 eV and ~0.28 eV with next-generation and cosmic-variance-limited lensing while remaining da
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The central claim is that if the bare vacuum energy is negative and sampled uniformly, and if universes are weighted by cumulative observation time, then the axion mass becomes anthropically confined to roughly one decade around the Hubble scale, and the probability of observing 0.1 < Ω_m < 0.9 is about 40%. The same logic anthropically disfavors slow-roll dark energy (which needs fine-tuned initial field displacement) and fast-roll (which gives too short a window of positive dark energy), leaving accelerated thawing as the typical dynamics. On current CMB, BAO, and Type Ia supernova data, the marginalized constraint δ_Ω = −0.0498 ± 0.0186 rejects ΛCDM (δ_Ω = 0) and phantom models (δ_Ω > 0)
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Under a hierarchical Gaussian process that co-samples kernel hyperparameters with cosmological parameters, conditioned on 37 cosmic-chronometer H(z) points and coupled to DESI DR2 BAO, compressed Planck distance priors, and Pantheon+ via a Monte-Carlo effective likelihood, the baseline posterior is w(z ≃ 0) = −0.80^{+0.26}_{-0.23} (about 0.8σ from −1). A CPL fit on the identical compressed pipeline improves nested ΛCDM by only Δχ² ∼ 1 (~1σ), and ablations that fix hyperparameters, drop supernovae or LRG1/2 BAO, change the kernel, or tighten the length-scale prior leave the median w(0) within ≲1σ of −1.
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When interacting ghost dark energy evolves inside the Kaniadakis-corrected flat Friedmann equations, the deformation parameter λ produces only mild shifts in the equation-of-state and deceleration histories, moderates the classical instability measured by the squared sound speed, and drives the statefinder trajectory toward the ΛCDM point {r,s}={1,0} with smaller present-day deviations as λ grows.
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A new class of Morris–Thorne wormholes sourced by fractional holographic dark energy, with redshift φ(r)=−0.1/r, satisfies the throat, flare-out and asymptotic-flatness conditions, remains free of curvature singularities, and becomes progressively less exotic and more thermodynamically regular as the fractional parameter γ is increased.
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Two-field dark energy with curved field-space geometry admits three distinct linear clustering mechanisms—effective sound-speed suppression of the light mode, dynamical excitation of the heavy mode by hard initial conditions, and tachyonic instability induced by negative field-space curvature—that can produce localized, mechanism-dependent deviations in the matter power spectrum and CMB temperature spectrum while the background evolution remains arbitrarily close to ΛCDM.
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The paper's central claim is that the ISW cross-correlation signal is present in the Quaia × Planck data at 2.8σ significance, with best-fit amplitude A_ISW ≈ 1.69 ± 0.61 relative to the fiducial Planck ΛCDM template. Split by redshift, the low-z bin (z̄ ≈ 0.97) gives 1.19 ± 0.56, the high-z bin (z̄ ≈ 2.10) gives 2.86 ± 1.62, and a joint fit over both bins gives 1.38 ± 0.53. The w0waCDM models used in the analysis, with parameters taken from recent baryon-acoustic-oscillation and weak-lensing constraints, predict ISW spectra lower than ΛCDM by at most about 20%, and fitting them to the data does not improve χ²; in fact the data prefer an amplitude above the ΛCDM template, in the opposite dir
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The central claim is that the entropic generalized Chaplygin gas — a unified dark fluid with equation of state p = -A/ρ^α, plus an entropy perturbation that drives the effective rest-frame sound speed to zero — is consistent at the background level with the full set of late-Universe distance and growth data, and that its only significant effect is a late-time bending of the distance-redshift relation. The paper argues this deformation moves the joint posterior in (H0, Ωm, S8) almost exclusively along directions controlled by the expansion history: with one supernova calibration it substantially shifts H0 and improves the fit over ΛCDM; with another calibration the two models nearly coincide.
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The central discovery is that a Ricci-tensor-squared correction to the Einstein–Hilbert action with a cosmological constant has very little observational room at the background level. For f_obs(R,χ)=R−2Λ+βχ, a joint fit to Type Ia supernovae, baryon acoustic oscillations, and compressed CMB distance priors yields β=(−6.6 +6.0/−8.1)×10^-5 (68% C.L.), with the profile likelihood showing β=0 within Δχ²<1. The reconstructed expansion rate, matter density parameter, deceleration parameter, and effective dark-energy equation of state all stay within about a percent of ΛCDM, and both AIC and BIC favor the nested ΛCDM limit. The paper interprets the result as a tight background-level upper bound on
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On the paper's own terms, the central discovery is a negative one: after sorting all proposed explanations by the part of the cosmological inference chain they modify, no model simultaneously preserves the CMB acoustic peak structure, the baryon-acoustic-oscillation standard ruler, the supernova distance-redshift relation, lensing, structure growth, and local absolute calibration. Early-time models like early dark energy can shrink the pre-recombination sound horizon, which is the necessary direction for raising the CMB-inferred H0, but the paper's reference chains show that uncalibrated data keep the early component small (fEDE ≈ 0.02–0.04 with H0 ≈ 67.8–69.4) and only a direct local-H0 cal
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The central claim is that the megamaser sample — six galaxies with geometric angular-diameter distances and recession velocities — yields marginalized estimates of the f(R) deviation parameter b close to zero for all three models (b ≈ 0.011 ± 1.00 for Hu-Sawicki, 0.023 ± 1.04 for Starobinsky, −0.005 ± 1.01 for ArcTanh), while H0 is constrained near 73 km/s/Mpc in every model. The paper interprets b ≈ 0 as the signature that these f(R) models reduce to the ΛCDM expansion history at low redshift. Since the 1σ uncertainties on b are of order unity, the claim is not that b is tightly measured, only that the data do not prefer any departure from ΛCDM. The model-comparison statistics (ΔAIC, ΔBIC ≤
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On the paper's own terms, the central discovery is that freeing the exponent in the BA kernel yields a three-parameter dark-energy equation of state, w_de(z) = w0 + (n/2) wa (1+z)|z|^(n−1)/(1+|z|^n), whose derived density takes the closed form X(z) = (1+z)^(3(1+w0)) (1+|z|^n)^(3wa/2). The paper claims this form removes the BA duplication for odd integer n, makes the location of the dark-energy transition depend on n instead of being fixed at z≈2.41, and that an MCMC analysis of CC+Pantheon++DESI+CMB gives n≈1.87 with BAn weakly preferred over BA and strongly preferred over ΛCDM by Bayesian evidence. The paper also reports that BAn predicts slightly less acceleration than BA, with deceleratio
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The paper's central result, Eq. (73), is that at second order in a gradient expansion the effective dark-energy equation of state is w_DE = -1 - [2/(9 H0^4 Omega_Lambda)] ( <Rbar^i_j Rbar^j_i> - (3/8)<Rbar^2> + (1/24)<Rbar>^2 ) ( g(a)/a^2 - (3/2) f(a)^2 ), where Rbar_ij is the Ricci tensor of a time-independent inhomogeneous three-metric, averages are over a fixed volume of matter particles, and f(a) and g(a) are functions built from hypergeometric integrals. The computation starts from the long-wavelength branch in which the spatial metric is frozen; at the next order, perturbations sourced by the background Ricci tensor generate both a kinetic back-reaction and a shift in the average spati
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The paper's central result is the gravitational-wave propagation equation h''_{L,R} + Ξ_{L,R} h'_{L,R} + ω²_{L,R} h_{L,R} = 0, where the friction Ξ_{L,R} and angular frequency ω_{L,R} are left/right polarization dependent. In the Palatini formalism, the dynamical Chern-Simons coupling generates both amplitude birefringence (a polarization-dependent damping) and velocity birefringence (a parity-violating, frequency-dependent phase shift); in the metric formalism the velocity term is absent. The f(R) sector enters through inverse powers of f_R = df/dR, so birefringence is enhanced when 0 < f_R < 1 and suppressed when f_R > 1. For three common f(R) models fitted to current cosmological data, f_
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The paper's central claim is that a vEDE component, which boosts the expansion rate only while deuterium is finishing its burning around T_D ≈ 0.03 MeV, can reconcile the measured primordial deuterium abundance with the higher baryon density inferred from CMB data in early dark energy cosmologies. Quantified as ΔH/H(T_D) = 0.087 +0.036/−0.037, this boost preserves D/H at the high baryon density while barely changing helium-4, reducing the tension from 3.1σ to 0.7σ. The timing of the extra expansion is the key: a constant radiation excess raises helium-4 too efficiently and fails to reconcile the two baryon-density determinations.
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The central claim is a new zero-mode selection rule for O(1) Euclidean D3-brane instantons in type IIB Calabi-Yau orientifolds. Using the equivariant fixed-point index theorem on the divisor D wrapped by the instanton, the paper computes χσ(D,O_D) = −k_E3E3O7/4 + N_O3/4, where k_E3E3O7 is the intersection number of D with the O7-plane and N_O3 is the number of O3-planes on D. This index directly feeds into the split Hodge numbers h^{2,0}_+ and h^{2,0}_-. A non-zero poly-instanton contribution requires h^{2,0}_+ = 1 and h^{2,0}_- = 0, which holds precisely when N_O3 = 8 + k_ddO7 for a deformation divisor. A pure K3 surface cannot satisfy this in a contributing O(1) configuration, but K3-like
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The paper claims that 'all three closures are tightly constrained to the vicinity of the LambdaCDM cosmographic fixed point, with Planck data driving the preferred evolution toward j0 ~ 1 and w_DE,0 ~ -1,' and that 'the reconstructed dark-energy evolution consistently exhibits a smooth freezing behaviour close to w=-1, without crossing the phantom divide.' If correct, current geometric observations do not require departures from the kinematic LambdaCDM condition j=1, and the dark-energy equation of state is not uniquely determined but depends on the reconstruction methodology.
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The central claim is that in the inverse-hierarchy branch of O(3) No-Scale Gravity, defined by m_theta << m_phi, the heavier angular field phi behaves as ultralight scalar dark matter (~10^-20 eV) and the lighter field theta acts as dynamical dark energy with m_theta <= H_0. The O(3)-breaking potential makes the initial dark-energy position theta/f_theta ~ pi/2 unstable while phi is frozen; as phi begins to oscillate and its amplitude decays, the interaction is suppressed and theta rolls toward its minimum, producing a transient kinetic-dominated phase and then late-time quintessence-like evolution. Although the physical equation of state w_theta always satisfies w_theta >= -1, the sin^4(the
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In a Planck-calibrated flat LambdaCDM background, matching the SH0ES measurement of H0 through a void-induced local expansion excess requires a present-day enclosed density contrast of about -0.44, roughly 50% deeper than the KBC benchmark of -0.3. A KBC-like void lowers the statistical tension from above 5 sigma to about 2 sigma, and the tension remains below 3 sigma only for voids with depths between about -0.64 and -0.22. Varying the dark-energy equation-of-state parameters w0 and wa over broad CPL ranges, including regions motivated by recent DES and DESI analyses, shifts the required depth by less than a percent, so dynamical dark energy cannot rescue a shallow KBC-like void. The paper
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On the paper's own terms, the central discovery is that a natural dark-matter–dark-energy interaction arises when the complex scalar potential is expanded near its maximum, and that this interaction makes the effective Hubble constant decrease with redshift in a way that matches the binned Pantheon supernova data. The key result is the closed-form solution ϵa = ϵa0 (1+z)^3 e^{-2δρ/σ0}, which shows the axion (dark matter) energy density is exponentially suppressed as the modulus displacement δρ grows; this suppression is what bends H0(z) downward. The best-fit value Δ = 0.00964 ± 0.00457 quantifies the effect, and the paper reports its statistical performance is between the empirical power-la
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The central claim is that the 100 µm CIB map, built from ~600 million WISE galaxies, is positively cross-correlated with the COSMIC MICROWAVE BACKGROUND temperature, and that this correlation is quantitatively consistent with the ΛCDM prediction. The null hypothesis of no correlation is rejected at p=0.02 (χ² test), and the best-fit amplitude A_kNN = 0.95 ± 0.20 gives a 4.8σ detection of the ISW/RS effect. The kNN-CDF analysis improves the detection significance by ~20% over the standard two-point angular power spectrum. The authors interpret this as dynamical evidence for the late-time evolution of gravitational potentials, consistent with a cosmological constant as the driver of cosmic acc
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The central claim is that a revised, corrected analysis of the same supernova sample recovers standard accelerating expansion. The full-sample deceleration parameter is -0.490 without any age correction, within the accelerating regime and close to the -0.55 expected in standard cosmology, and remains negative (-0.267) after applying the proposed progenitor-age magnitude correction. Hemisphere-split fits using the corrected CMB dipole direction give -0.527 and -0.464, and redshift, host-mass and colour subsamples all remain mutually consistent and accelerating. The paper therefore argues that the earlier reports of near-zero acceleration or deceleration originated from the coordinate error an
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The core claim is that the stopping criterion for the repetitive Penrose process in this spacetime is fixed by Particle 0. Working at unit incident energy (E-hat_0 = 1) and imposing vanishing radial momenta for all three particles at each decay, the authors derive analytic expressions for decay products and iterate the black hole's mass, spin, irreducible mass, and structure parameter. They find the ordering a-hat_min,1 < a-hat_min,2 < a-hat_min,0 throughout the parameter space, so the highest threshold—the one that halts extraction—belongs to Particle 0 and coincides with the co-rotating marginally bound orbit. This threshold rises slowly from one iteration to the next; when the evolving sp
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Imposing a vanishing speed of sound on the TDiff scalar action frees the coupling functions only through three channels—a linear kinetic coupling, a nonlinear kinetic coupling with μ₀ = 0, or a nonlinear coupling with constant potential—and each channel is mapped by field redefinitions to the common action S = ∫√g [X − V(ψ) + φ(X − βV(ψ) − γ)], with β and γ free parameters and φ a Lagrange multiplier enforcing X = βV(ψ) + γ. The paper shows this is exactly the mimetic constraint. The energy-momentum tensor then reads as dust plus vacuum energy, with the vacuum piece p_λ = −ρ_λ and an interaction kernel Q^ν = (β−1)V′(ψ)∇^νψ; when β = 1 or V(ψ) is constant the kernel vanishes and the ΛCDM dark
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The paper's central claim is that the generalized mass-to-horizon entropy class, despite its additional parameters, is observationally forced back to standard Bekenstein–Hawking thermodynamics: the entropy exponent satisfies |m−1| ≲ 10⁻⁴ when the MHR coupling is fixed and ≲10⁻³ when the coupling is free, and the derived coupling and entanglement amplitude deviate from their ΛCDM values only along degeneracy directions. It further claims that the apparent resolution of the Hubble tension is an artifact: adding parameters absorbs the CMB–SH0ES discrepancy, pushing h to 0.70–0.71, but the Bayesian log-evidence is negative for every extension in every dataset combination (−16 ≲ Δ ln Z ≲ −1). The
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The paper's central claim is that a single vacuum bubble—a spherical region whose vacuum energy density is a fraction β of the exterior value, nucleated at redshift z_nuc—predicts sharp, localized features in the Alcock–Paczynski BAO stretch parameters. When β≈0.9 and z_nuc≈1.4, the binned parallel and perpendicular stretches qualitatively track the DESI DR2 measurements. However, the same geometry forces an off-centre observer to see an angle-dependent CMB redshift; the induced dipole, the remote-dipole kSZ contribution, the velocity-reconstruction monopole, and the modified distance to last scattering all constrain the bubble, and the DESI-matching region of parameter space is excluded to
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The paper's central claim is that the dark-matter equation of state is not exactly zero today. It stays consistent with pressureless CDM at early times but becomes mildly negative at late times; the strongest dataset combination gives w0 = -0.060 with 68% errors +0.013/-0.028, a deviation from zero at about 2.3σ, rising to about 3.0σ when growth-rate data are added. The transition occurs at scale factor a_t = 0.41, i.e. redshift around 1.4. Interpreting the negative late-time pressure as an effective bulk-viscous dark matter, the paper argues that a substantial part of the DESI preference for phantom-like dynamical dark energy can be absorbed by dark-matter physics rather than by new physics
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For a separately conserved effective dark-energy sector whose density crosses zero smoothly from negative to positive at redshift z† with finite odd order n, the paper proves that I_de=ρ_de+p_de and M_de=ρ_de+3p_de are negative in a punctured neighborhood of the crossing and non-positive at the crossing itself, while the ratio w_de=p_de/ρ_de develops a pole with the universal residue n(1+z†)/3. Because M_de is the quantity entering the Raychaudhuri source, the sector is already Raychaudhuri-repulsive on the negative-density side whenever it is attractive at high redshift, and the familiar conditions w<-1/3 and w=-1 are only branch-dependent ratio representations of M_de<0 and I_de=0. Under t
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For each model, the paper substitutes the modified Friedmann equation into the standard BBN freeze-out relation H(Tf) = Λ(Tf), solves for the matter energy density from the field equations, fixes a coupling using the present dark-energy density ΩDE0 ≈ 0.7, and derives |ΔTf/Tf| as a function of the exponent n. It finds that the predicted deviation crosses the observational bound at n ≈ 0.3721 for Model 1, while Models 2–4 have somewhat larger but still narrow allowed intervals. The helium mass fraction Yp curves remain inside the observed band only for restricted n ranges. The authors read these results as showing that f(R,G,T) gravity is consistent with BBN and therefore a viable extension o
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The authors build end-to-end simulated observations: a low-redshift 21 cm intensity mapping experiment plus a galaxy survey with 40 tomographic bins (seven of which pass signal-to-noise cuts), including synchrotron and free-free foregrounds. They remove the foregrounds blind, compute transfer functions from hundreds of injected Gaussian hydrogen simulations, and correct the cross-power spectrum amplitudes. A Bayesian fit to the two-parameter dark energy equation of state (w0, wa) then yields posteriors whose best-fit values match the input cosmology. Individual data sets can show skewed one-dimensional posteriors, but when all seven sets are combined the skewness is suppressed and no signifi
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Eq. (5.8)/(1.1): (1−n_s)^2 − r/3 ≃ [3(1+w0)/(2F(Ω_DE))]^2 with F(Ω_DE)≈0.45; the same coupling ξ simultaneously sets the departure from Starobinsky inflation and the DE thawing signal. The paper states: 'the same field-space geometry predicts both the departure from pure Starobinsky inflation and the departure of DE from a cosmological constant' (§6). If true, the model fixes the DE equation-of-state slope from the inflationary attractor, yielding (w0,w_a)≃(−0.992,−0.011) for ξ=0.01.
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The full Rolling Galileon theory space is closed under field redefinitions and characterized by two invariant functions k(φ) and q(φ); the analytic conditions for a late-time phantom crossing, positive ISW, and health of the Vainshtein-screened force in voids are collectively satisfied by an increasing braiding strength (kφ<0, q>0, qφ<0), and the minimal k-q model fits expansion data with Δχ²_MAP ≈ -11.7 relative to ΛCDM.
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The central claim: apparent phantom crossing can arise from a well-defined interacting dark sector, not a fundamental phantom field. In the DADB model, the dark QCD axion's effective potential depends on dark-baryon density; the baryon mass varies as the axion rolls, falling before recombination and rising afterwards. This non-monotonic mass evolution fits the CMB while producing an apparent phantom crossing over the BAO/supernova epoch. Fitted to CMB, BAO, and recalibrated supernova data, the best model beats ΛCDM by Δχ²=-14.48 with three extra parameters. The same dynamics yields an early-dark-energy component peaking at ~0.8% of total density, too small to resolve the Hubble tension.
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For the f(R,T)=R+λT^ε gravity model in a flat FLRW universe with radiation, the paper constructs the expansion history and a full χ² likelihood from CMB, BAO, cosmic chronometers, and Type Ia supernova data, including correlations. Marginalizing over nuisance parameters (ξ, ω_b, H_0, and M), it obtains the relative probability distribution for ε, centered at ε=0.010 with 68% bounds of +0.013 and −0.021. The standard value ε=0 is comfortably inside this range. The authors interpret this as no preference for the modified term, with the tight constraint driven mainly by the Pantheon+SH0ES supernovae and DESI DR2 BAO data.
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On the paper's own terms: in a flat Friedmann universe with Einstein–Cartan torsion and a separately conserved matter sector, the torsion scalar Phi satisfies Phi = Phi0 a^-3 and enters the Friedmann constraint as -3Phi0^2 a^-6, an effective stiff fluid of negative energy density. Adding the holographic density rho_hol = 3c^2 H^2, the deceleration parameter becomes q = (rho - 12Phi^2)/(2(rho - 3Phi^2)), independent of c^2: the holographic component merely renormalizes the constraint. Acceleration occurs if and only if rho < 12Phi^2, i.e. only for a_bar <= a < 4^{1/3} a_bar, the post-bounce transient. Placing that window at observable redshifts forces H^2=0 in our recent past. The resulting b
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The paper's discovery, on its own terms, is that combining a Hayward regular core with a Kiselev quintessence field moves the ISCO to 4.6827 MBH at j = 0.4 and deepens the binding energy there enough to raise the disk efficiency from 7.51% to 8.71%, while the nonzero inner torque—entering through the vertical epicyclic frequency—makes the flux ratio Tin/I(r) diverge at the ISCO in a way that is amplified by the modified geometry. The authors prove analytically, and confirm numerically to better than 10^-8%, that η does not depend on α, because E(rISCO) comes purely from geodesics. They identify the viscosity amplification ratio (Hayward+DE vs its own NTP baseline) as the cleanest observable,
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The authors claim that the L(Hβ)–σ relation remains a standard candle without significant evolution all the way to redshift ~14. The joint fit of 243 anchor and HII galaxies gives log L(Hβ) = (5.00±0.11) log σ + (33.27±0.14) in cgs units, with sub-sample fits (z<0.16, z>3) consistent at 1σ. Using this relation as a distance estimator, the combined sample under flat ΛCDM yields h=0.725±0.040 and Ωm=0.308(+0.043/-0.053); allowing a constant dark-energy equation of state gives w0=-0.96(+0.53/-0.21), and a CPL parametrisation gives w0=-0.92(+0.57/-0.34), wa=-0.48(+0.60/-1.50), all compatible with concordance cosmology. The claim is that HII galaxies provide a fully independent tracer of the expa
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The authors propose heuristic formulas, Eqs. (10)–(11), in which both the mean τ̄ and variance Sτ of the primordial spin factor decrease from a plateau value as an exponential-with-power-law function of q, with a threshold value of q below which the decline is mild and above which it is steep. They find that three best-fit parameters in each formula — a normalization, a threshold, and a power-law index — remain constant, within errors, across ΛCDM cosmologies with different dark-energy densities and wCDM cosmologies with different equations of state, and across nine combinations of the two smoothing scales. Together with the Gamma-distribution form of p(τ), this means the entire spin-factor
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The central claim is that the Type 3 interacting dark energy model leaves a specific, measurable signature in void radial velocity statistics. For negative momentum coupling β, the extra friction suppresses both the outflow of matter from void interiors and the scatter of tracer velocities around voids, relative to the uncoupled case. Within the 1σ region allowed by current data, the fractional change in the velocity-profile spans reaches about 30% for the strongest couplings and steepest potentials, and the dependence on β and λ is captured by a four-parameter quadratic regression with adjusted R² above 0.95 for both halo- and particle-traced voids. The paper concludes that void velocity st
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On its own terms, the paper's finding is a hierarchy. In the baseline analysis, ΛCDM sits at a 5.4σ (ΔDMAP) tension with the locally calibrated supernova magnitude, and no contender closes the gap completely. The best performers are early-time mechanisms: axion-like early dark energy reaches a residual 2.5σ with −ΔAIC ≈ 23 and log-Bayes ≈ 10.5; early modified gravity, Rock'n'Roll, and NEDE cluster at 2.7–3.1σ. The varying-electron-mass model is the only non-early contender to pass the selection thresholds, at roughly 4σ; radiation and late-time groups stay near or above 4.5σ. Without ACT data, most radiation and recombination models recover to 3–3.5σ, so the preference for early dark energy
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The central claim is that, in a common statistical framework applied to the baseline CMB+BAO+SN dataset, the four early-energy models (axion-like early dark energy, cold NEDE, early modified gravity, and its Rock'n'Roll limit) are the only contenders that both reduce the residual calibration tension to the 2.5–3.6σ level and achieve strong joint-fit support over ΛCDM (−ΔAIC > 10 and ln BF > 3). A localized non-radiative contribution near matter–radiation equality is thus identified as the most effective mechanism, because it shrinks the sound horizon while leaving the detailed high-multipole CMB spectra and the low-redshift distance relation intact. The paper does not claim any model fully r
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On the paper's own terms, the central discovery is that the per-redshift posterior weighting—computing P(θ,z|D) ∝ exp[-(O_pred(z,θ) - O_GP(z))²/(2σ_GP(z)²)] for each parameter realization against the GP mean and variance—produces most-likely parameters that vary with redshift rather than staying constant. For the single-parameter Brans–Dicke subclass, the most-likely ω(z) makes BD more likely than the ΛCDM best-fit within 0.4<z<1.7. For the Cubic Galileon subclass, the most-likely physical dark-energy density ω0Λ is not constant: in the H(z)-only reconstruction it approaches zero at z>2, and in the combined H(z)+BAO reconstruction it rises and falls in a pattern correlated with the reconstru
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The central claim is that the zero-temperature, one-loop radiative (Coleman-Weinberg) potential of the weak axion is dominated by the quartic invariant in Eq. (37), with an amplitude Λν fixed uniquely by the neutrino masses and the PMNS matrix. In the flavor-democratic limit the potential is V_CW(a) ≈ −Λν^4 cos((a−a0)/f + δν), and for normal ordering with m1 ≈ 0 the amplitude is approximately Λν ≈ 2.3 meV times the square root of |cosδ_CP/0.52 + sin(θ23−π/4)/0.055|; across present data sets this yields 1–4 meV. Both the height and the phase of the potential are determined by the same spurions, with the Majorana phases mainly shifting the minimum. The construction's key feature is that the ax
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Dissipative Chaplygin gas, DBI, and scalar-field cosmologies in coincident f(Q) gravity can be systematically assessed for viability, dynamical behaviour, and perturbative stability against CC, Pantheon+SH0ES, Hubble, and DESI observations; the analysis isolates the subset of these frameworks that still produce late-time acceleration without unstable modes.
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Within analytic perturbations around the Hu-Sawicki class of f(R) models that pass the listed theoretical viability conditions, current background data (DESI DR2 BAO + Pantheon+) permit only limited deviations from ΜDM; the largest effects appear at late times and are rapidly suppressed at higher redshift, leaving Om(z) nearly constant and the effective dark-energy equation of state only weakly evolving.
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The central claim is that the combined system—interacting viscous generalized ghost dark energy embedded in f(G) gravity—admits a smooth reconstruction of the Gauss–Bonnet correction f(G) under the hybrid expansion law, and that this reconstructed theory behaves as a viable dark-energy model: it produces a late-time de Sitter attractor, is classically stable for suitable parameters, satisfies the generalized second law of thermodynamics (with both Bekenstein–Hawking and Barrow entropy), and is consistent with cosmic-chronometer Hubble data. The calculation equates the geometric f(G) terms in the modified Friedmann equations to the ghost dark-energy density, yielding a second-order differenti
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Observational manifestations of the ZKDR parameter α(z) admit two equivalent interpretations—one as a dynamical dark-energy model and one as weak gravitational lensing in a Λ universe—thereby establishing a degeneracy between those scenarios that can be broken by testing sky isotropy of α(z) at fixed redshift.
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In the phenomenological ξ IDE model the combination ξ + 3w_X is negative for every dataset combination examined, corresponding to energy transfer from dark energy to dark matter; the tightest constraint is ξ + 3w_X = −0.035 ± 0.023 (1.52σ from zero) for CMB + DESI DR2 + CC + Union3, so current data supply only a weak indication of a non-zero dark-sector interaction while Bayesian evidence continues to prefer ΛCDM.
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A data-driven nonparametric expansion–growth framework that simultaneously reconstructs w_de(z) and the dark-sector coupling, by incorporating a freely evolving interacting-matter density into the linear growth equation, breaks the background degeneracy between time-varying dark energy and dark-sector energy exchange; applied to current expansion and growth data, both the reconstructed coupling and w_de(z) stay consistent with the ΛCDM limit over 0 ≲ z ≲ 2, with no statistically significant evidence for nonzero interaction or dark-energy dynamics.
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An N×2pt analysis that jointly uses SKA-Mid AA4 continuum galaxy clustering, weak lensing and galaxy–galaxy lensing together with HI intensity mapping and HI galaxy clustering is forecast to deliver approximately one-percent precision on the principal ΛCDM parameters, with the combination of continuum and HI probes supplying the decisive degeneracy breaking.
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Within the class of symmetry-protected scalar portals (quartic, trilinear, derivative) and the minimal fermionic Yukawa coupling, no single-mediator model can simultaneously satisfy technical naturalness and resolve the observed S8 deficit. The trilinear and Yukawa portals each demand a phenomenological coupling that exceeds the one-loop Coleman–Weinberg bound by ~26 orders of magnitude (tuning Δ ~ 10^52, still ~10^50 after SUSY cancellation). The quartic portal requires λ ~ O(1–10) against a bound λ ≲ 10^{-86} (Δ ~ 10^87). The derivative portal is technically natural by shift symmetry but saturates at ≲4 % structure suppression once momentum exchange reaches Hubble, too little to close the
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After SALT2 light-curve standardization, Type Ia supernovae exploding in younger local environments (local luminosity-weighted age split near log10(age/yr) = 9.084) are systematically fainter by 0.163 ± 0.031 mag (5.2σ). Joint fits reduce the global mass step from 0.071 mag (2.0σ) to 0.028 mag (0.9σ) and the local mass step from 0.087 mag (2.4σ) to 0.012 mag (0.3σ), while the age step remains ~0.156–0.157 mag at >4σ. Roughly half to three-fifths of the mass-step variance is therefore age-driven, and adding the age step lowers weighted residual scatter from 0.1550 to 0.1376 mag.
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For a generic choice of the beyond-Horndeski EFT parameters, the multipole moments of the fifth force are not screened in the region where the monopole component is screened; the gravitational potential instead exhibits a characteristic oscillatory radial dependence in its multipole components. Even when the EFT parameters are tuned so that graviton decay into dark energy is practically absent, the Vainshtein mechanism remains insufficient to screen the fifth force around a nonspherical source.
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If left uncorrected, the measured FPA-dependent wavelength shifts (ranging roughly +6 to -80 Å across the 18 SCAs) introduce a redshift-dependent distance-modulus bias that propagates to Δw0 ≈ -0.066 and Δwa ≈ 0.236, exceeding the forecast statistical uncertainties of 0.025 and 0.114 and rendering the survey systematics-limited. Detector-specific filter curves recover unbiased constraints, and characterization of the shifts to within ~20% keeps the bias below the statistical noise floor; the coherent 0.06% absolute-calibration residual is already subdominant.
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The authors establish that the interplay of a curvature-triggered fermion-condensate vacuum and geometric backreaction from nonlinear structure formation produces a smooth, finite late-time phantom-crossing evolution of the total dark-energy equation of state. The condensate remains frozen until R drops below Rc, after which its energy density builds while backreaction regularizes the would-be singularity; for benchmark Omega_BR(z=0) = 0.0572 the effective CPL parameters are z* ~ 0.35, w0 ~ -0.76, wa ~ -0.93, consistent with DESI+CMB+DESY5/PantheonPlus/Union3 analyses.
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Cosmological observations of single-scalar dark energy are fundamentally limited: they can at most constrain a small number of EFT parameters that govern the scalar’s late-time dynamics. Even after Stage-IV surveys, the problem of underdetermination will persist, so the ultimate viability of these models hinges on improved low-redshift growth measurements and a consistent understanding of gravitational screening.
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The combined use of DES optical photometry with WISE W1 and W2 mid-infrared data improves the photometric-redshift metrics (bias, sigma_68 scatter and Banerji outlier fraction) relative to optical-only estimates, particularly at higher redshifts; adding VHS near-infrared bands at the depths explored yields no further statistically meaningful gain for z less than 1.5.
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The discrepancy between DESI and SDSS on whether the Universe is currently accelerating is driven by the ~0.15 difference in their lowest effective redshift anchors (z_eff ≈ 0.295 for DESI vs. z_eff ≈ 0.15 for SDSS). In the CPL parametrization, w_0 and q_0 are present-day quantities that require low-redshift data to constrain directly; without such an anchor, the reconstruction extrapolates and q_0 drifts positive. Two tests confirm this: adding Pantheon+ supernovae to DESI restores acceleration (q_0 = −0.37), and removing SDSS's low-z MGS anchor shifts SDSS's q_0 from −0.22 toward −0.10.
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A Z_N-symmetric multi-copy dark-QCD axion, with controlled Z_N breaking induced solely by reheating into one copy that supplies dark-pion dark matter, simultaneously generates a technically natural dark-energy scale, restores the physical axion periodicity, sets the dark-matter abundance, and drives late-time rolling that produces an effective phantom equation of state without tuned cancellations.