Inflaton-gluon coupling during inflation requires p=2 plateau models to produce isocurvature-free QCD axion dark matter.
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The Unity of Cosmological Attractors
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abstract
Recently, several broad classes of inflationary models have been discovered whose cosmological predictions are stable with respect to significant modifications of the inflaton potential. Some classes of models are based on a non-minimal coupling to gravity. These models, which we will call $\xi$-attractors, describe universal cosmological attractors (including Higgs inflation) and induced inflation models. Another class describes conformal attractors (including Starobinsky inflation and T-models) and their generalization to $\alpha$-attractors. The aim of this paper is to elucidate the common denominator of these models: their attractor properties stem from a pole of order two in the kinetic term of the inflaton field in the Einstein frame formulation, prior to switching to the canonical variables. We point out that $\alpha$- and universal attractors differ in the subleading corrections to the kinetic term. As a final step towards unification of $\xi$ and $\alpha$ attractors, we introduce a special class of $\xi$-attractors which is fully equivalent to $\alpha$-attractors with the identification $\alpha = 1+{1\over 6\xi}$. There is no theoretical lower bound on $r$ in this class of models.
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A one-parameter family of α-attractor potentials interpolates between exponential and polynomial attractor predictions, letting n_s scan the range preferred by CMB+DESI.
Negative field-space curvature enhances post-inflationary Ricci scalar oscillations and boosts CGPP dark matter number density by up to an order of magnitude relative to flat field-space cases, with nontrivial relic abundance dependence on spectator mass and reheating temperature.
Inflaton-gluon coupling induces early QCD confinement to suppress axion isocurvature perturbations and enable axion dark matter production in alpha-attractor inflation models.
The paper introduces new exponential and polynomial supergravity ξ-attractor models in the Jordan frame with non-minimal coupling and shows that Palatini gravity with independent affine connection has no supergravity embedding.
Non-minimal coupling of the inflaton to the Holst invariant in metric-affine gravity induces quasi-pole kinetics that generate an exponential plateau potential and Starobinsky-equivalent predictions regardless of the bare potential.
Nonminimal derivative coupling realizes the Harrison-Zeldovich attractor for monomial, hilltop, and α-attractor E-models, pulling them to the scale-invariant spectrum suggested by ACT data.
Using combined CMB and LSS observations, the analysis sets 95% CL upper limits on oscillatory amplitudes at approximately 2% of A_s and a MAP value of 0.034 for the particle production coupling constant, finding no statistical preference for the extended models.
Inflaton accretion during reheating drives non-linear PBH mass growth that extends lifetimes and amplifies emitted SGWB by multiple orders of magnitude.
Derives conditions on branch parameters for controlled inflationary plateaus in penumbral monodromic valleys, with an exactly solvable family targeting r ~ 10^{-3} and alpha_s ~ -r/2.
New ξ-attractors with non-minimal coupling and non-canonical kinetics yield Einstein-frame exponential and polynomial potentials whose ns spans 1-2/N to 1-1/N and r can reach zero as ξ grows, fitting Planck, BICEP/Keck, ACT, SPT, and DESI data, plus a supergravity realization.
High-frequency primordial gravitational waves extend to higher frequencies due to post-inflation inflaton dynamics, and their detailed spectrum shape can distinguish inflation models.
Polynomial α-attractor P-models of inflation accommodate Planck and Planck+ACT CMB data for ranges of reheating temperatures when decays and fragmentation are included.
Final Planck CMB data confirms the flat 6-parameter ΛCDM model with Ω_c h² = 0.120 ± 0.001, Ω_b h² = 0.0224 ± 0.0001, n_s = 0.965 ± 0.004, τ = 0.054 ± 0.007, H_0 = 67.4 ± 0.5 km/s/Mpc, and no strong evidence for extensions.
A single power-law effective scaling anchored at today's Hubble rate is extrapolated to inflation and required to match the Starobinsky plateau within O(1) factors, selecting γ ≈ 0.49 and β ≈ 0.68.
Dilaton from broken scale symmetry meets all conditions for non-compact QCD axion cosmology including non-periodicity and timely domain-wall collapse.
Reheating temperature and equation-of-state parameter assumptions in Weyl-invariant Einstein-Cartan gravity models significantly alter predicted inflationary observables.
Differences in inflationary energy scales between Einstein and Jordan frames produce distinct reheating e-folding numbers and temperatures, leading to contrasting thermal histories with potential observational signatures.
Multi-phase non-minimal inflation in metric and Palatini gravity predicts ns between 0.93 and 0.98, r up to 0.03 in metric but below 10^{-5} in Palatini, with non-thermal DM and leptogenesis viable for couplings in the 10^{-7} to 10^{-3} range.
Gravity-mediated production of scalar and vector dark radiation yields Planck 2018 constraints on reheating temperature T_RH and background equation of state w_Φ, with comparisons to right-handed neutrinos, ALPs, and a generic spin-2 mediator.
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Jordan Frame in Supergravity and Cosmology
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Quasi-pole inflation in metric-affine gravity
Non-minimal coupling of the inflaton to the Holst invariant in metric-affine gravity induces quasi-pole kinetics that generate an exponential plateau potential and Starobinsky-equivalent predictions regardless of the bare potential.
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Harrison-Zeldovich attractor: From Planck to ACT results
Nonminimal derivative coupling realizes the Harrison-Zeldovich attractor for monomial, hilltop, and α-attractor E-models, pulling them to the scale-invariant spectrum suggested by ACT data.
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Constraining primordial oscillations and inflationary particle production with Planck, ACT DR6, and DESI DR2
Using combined CMB and LSS observations, the analysis sets 95% CL upper limits on oscillatory amplitudes at approximately 2% of A_s and a MAP value of 0.034 for the particle production coupling constant, finding no statistical preference for the extended models.
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Inflaton Accretion onto Primordial Black Holes During Reheating
Inflaton accretion during reheating drives non-linear PBH mass growth that extends lifetimes and amplifies emitted SGWB by multiple orders of magnitude.
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Controlled Penumbral Inflation from Monodromic Valleys
Derives conditions on branch parameters for controlled inflationary plateaus in penumbral monodromic valleys, with an exactly solvable family targeting r ~ 10^{-3} and alpha_s ~ -r/2.
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New Exponential and Polynomial $\xi$-attractors
New ξ-attractors with non-minimal coupling and non-canonical kinetics yield Einstein-frame exponential and polynomial potentials whose ns spans 1-2/N to 1-1/N and r can reach zero as ξ grows, fitting Planck, BICEP/Keck, ACT, SPT, and DESI data, plus a supergravity realization.
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High Frequency Spectrum of Primordial Gravitational Waves
High-frequency primordial gravitational waves extend to higher frequencies due to post-inflation inflaton dynamics, and their detailed spectrum shape can distinguish inflation models.
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Testing $\alpha$-attractor P-model of inflation by Cosmic Microwave Background radiation
Polynomial α-attractor P-models of inflation accommodate Planck and Planck+ACT CMB data for ranges of reheating temperatures when decays and fragmentation are included.
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Planck 2018 results. VI. Cosmological parameters
Final Planck CMB data confirms the flat 6-parameter ΛCDM model with Ω_c h² = 0.120 ± 0.001, Ω_b h² = 0.0224 ± 0.0001, n_s = 0.965 ± 0.004, τ = 0.054 ± 0.007, H_0 = 67.4 ± 0.5 km/s/Mpc, and no strong evidence for extensions.
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A cross-epoch endpoint-consistency test of a single effective scaling from dark energy to inflation
A single power-law effective scaling anchored at today's Hubble rate is extrapolated to inflation and required to match the Starobinsky plateau within O(1) factors, selecting γ ≈ 0.49 and β ≈ 0.68.
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QCD axion from broken scale symmetry
Dilaton from broken scale symmetry meets all conditions for non-compact QCD axion cosmology including non-periodicity and timely domain-wall collapse.
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Reheating in geometric Weyl-invariant Einstein-Cartan gravity
Reheating temperature and equation-of-state parameter assumptions in Weyl-invariant Einstein-Cartan gravity models significantly alter predicted inflationary observables.
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Einstein or Jordan: seeking answers from the reheating constraints
Differences in inflationary energy scales between Einstein and Jordan frames produce distinct reheating e-folding numbers and temperatures, leading to contrasting thermal histories with potential observational signatures.
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Induced Multi-phase Inflation with Reheating: Leptogenesis and Dark Matter Production in Metric versus Palatini
Multi-phase non-minimal inflation in metric and Palatini gravity predicts ns between 0.93 and 0.98, r up to 0.03 in metric but below 10^{-5} in Palatini, with non-thermal DM and leptogenesis viable for couplings in the 10^{-7} to 10^{-3} range.
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CMB signatures of gravity-mediated dark radiation in $\mathbf{\Delta N_{\rm eff}}$
Gravity-mediated production of scalar and vector dark radiation yields Planck 2018 constraints on reheating temperature T_RH and background equation of state w_Φ, with comparisons to right-handed neutrinos, ALPs, and a generic spin-2 mediator.
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In the Realm of the Hubble tension $-$ a Review of Solutions
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