Standard non-thermal leptogenesis works at arbitrarily low reheating temperatures above the BBN bound when the inflaton potential has a quartic minimum (k≥4), because the inflaton's evolving mass kinematically shuts off RHN production early.
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Particle Physics Models of Inflation and the Cosmological Density Perturbation
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This is a review of particle-theory models of inflation, and of their predictions for the primordial density perturbation that is thought to be the origin of structure in the Universe. It contains mini-reviews of the relevant observational cosmology, of elementary field theory and of supersymmetry, that may be of interest in their own right. The spectral index $n(k)$, specifying the scale-dependence of the spectrum of the curvature perturbation, will be a powerful discriminator between models, when it is measured by Planck with accuracy $\Delta n\sim 0.01$. The usual formula for $n$ is derived, as well as its less familiar extension to the case of a multi-component inflaton; in both cases the key ingredient is the separate evolution of causally disconnected regions of the Universe. Primordial gravitational waves will be an even more powerful discriminator if they are observed, since most models of inflation predict that they are completely negligible. We treat in detail the new wave of models, which are firmly rooted in modern particle theory and have supersymmetry as a crucial ingredient. The review is addressed to both astrophysicists and particle physicists, and each section is fairly homogeneous regarding the assumed background knowledge.
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Calibrates a one-parameter semi-analytic damping model for oscillatory primordial power spectrum features using N-body simulations and validates sub-percent accuracy via GPR emulation when modulation frequency is high enough.
A shear-free locally FLRW lattice framework for single-field inflation captures spatially varying expansion, curvature corrections, and nonlinear δN observables at a fraction of the cost of full numerical relativity.
Generalizes neutrino isocurvature by introducing a mixing angle for the neutrino-matter perturbation ratio and derives first Planck limits on the angle.
An effective constrained scalar-Gauss-Bonnet inflation model yields n_s ≃ 0.958 and r ≃ 2.7×10^{-4} while the exact theory has no propagating scalar degree of freedom.
Finite recombination thickness introduces Gaussian smoothing in ln k to the primordial power spectrum, producing non-trivial differences between TT and EE spectral indices that may be detectable in future CMB data.
NANOGrav data favors a blue-tilted tensor spectrum with nt ≈ 2.2, radiation-dominated reheating, and alpha-vacuum states over standard Bunch-Davies, with a frequency-dependent alpha suggested to resolve the blue-tilt tension.
Using S2 star periastron precession, the work constrains ultralight scalar dark matter mass ratios to below 10^{-3} or 1 and improves quadratic coupling bounds for masses 10^{-20} to 10^{-18} eV.
A spectator scalar field with strong portal coupling to the inflaton sources a stochastic gravitational wave background reaching Ω_GW h² ∼ 10^{-11} at frequencies 10^7-10^8 Hz for benchmark parameters σ/λ ≃ 10^4 and T_reh = 2×10^{14} GeV.
Generalized no-scale models with R=2/(3α) for α≠1 or non-minimal gauge couplings allow unsuppressed inflaton decays, producing calculable reheating temperatures and (n_s,r) predictions.
Four Einstein-Gauss-Bonnet inflationary models are reconstructed from a chosen tensor-to-scalar ratio and shown to satisfy ACT and GW170817 constraints including scalar perturbation amplitude.
A holographic f(Q) = ζ Q^n model yields slow-roll inflation consistent with Planck 2018 and late-time expansion compatible with CC+BAO data via CPL parametrization, with mild high-z deviations from ΛCDM.
Einstein-Gauss-Bonnet inflation can yield positive spectral-index running with a viable era under ACT-like hints, while scalar-field and F(R) models largely cannot.
Derives slow-roll observables and consistency relations for scalar-tensor Gauss-Bonnet inflation and fits a specific model to Planck data.
MCMC analysis of sixteen ghost-free f(R,G) inflation models shows all reproduce ns ≈ 0.97 at 60 e-folds with stable μ ≈ 0.1, preference set by Hubble parametrization.
Three standard inflationary potentials remain compatible with Planck, BICEP/Keck, DESI DR2, and ACT DR6 data when placed in minimally coupled f(R,T)=R+16πGλT gravity for suitable ranges of the model parameters and coupling λ.
Modified gravity theories supply viable mathematical frameworks for inflation, bounces, and dark energy eras that match observational data.
citing papers explorer
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Leptogenesis and Low Reheating Temperatures
Standard non-thermal leptogenesis works at arbitrarily low reheating temperatures above the BBN bound when the inflaton potential has a quartic minimum (k≥4), because the inflaton's evolving mass kinematically shuts off RHN production early.
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(The) Wiggles going non-linear
Calibrates a one-parameter semi-analytic damping model for oscillatory primordial power spectrum features using N-body simulations and validates sub-percent accuracy via GPR emulation when modulation frequency is high enough.
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Nonlinear Lattice Framework for Inflation: Bridging stochastic inflation and the $\delta{N}$ formalism
A shear-free locally FLRW lattice framework for single-field inflation captures spatially varying expansion, curvature corrections, and nonlinear δN observables at a fraction of the cost of full numerical relativity.
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Generalized neutrino isocurvature
Generalizes neutrino isocurvature by introducing a mixing angle for the neutrino-matter perturbation ratio and derives first Planck limits on the angle.
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Effective Constrained Scalar--Gauss--Bonnet Inflation Motivated by $f(R,\mathcal{G})$ Gravity
An effective constrained scalar-Gauss-Bonnet inflation model yields n_s ≃ 0.958 and r ≃ 2.7×10^{-4} while the exact theory has no propagating scalar degree of freedom.
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Recombination Thickness as an Uncertainty in Inflationary Observables
Finite recombination thickness introduces Gaussian smoothing in ln k to the primordial power spectrum, producing non-trivial differences between TT and EE spectral indices that may be detectable in future CMB data.
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Constraints on the inflationary vacuum and reheating era from NANOGrav
NANOGrav data favors a blue-tilted tensor spectrum with nt ≈ 2.2, radiation-dominated reheating, and alpha-vacuum states over standard Bunch-Davies, with a frequency-dependent alpha suggested to resolve the blue-tilt tension.
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Constraining Ultralight Scalar Dark Matter in the Galactic Center with the S2 Orbit
Using S2 star periastron precession, the work constrains ultralight scalar dark matter mass ratios to below 10^{-3} or 1 and improves quadratic coupling bounds for masses 10^{-20} to 10^{-18} eV.
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Gravitational Waves from Matter Perturbations of Spectator Scalar Fields
A spectator scalar field with strong portal coupling to the inflaton sources a stochastic gravitational wave background reaching Ω_GW h² ∼ 10^{-11} at frequencies 10^7-10^8 Hz for benchmark parameters σ/λ ≃ 10^4 and T_reh = 2×10^{14} GeV.
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Reheating in No-Scale Models of Inflation
Generalized no-scale models with R=2/(3α) for α≠1 or non-minimal gauge couplings allow unsuppressed inflaton decays, producing calculable reheating temperatures and (n_s,r) predictions.
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Reconstructing ACT-compatible and GW170817-compatible Einstein-Gauss-Bonnet Inflation from the Observational Indices
Four Einstein-Gauss-Bonnet inflationary models are reconstructed from a chosen tensor-to-scalar ratio and shown to satisfy ACT and GW170817 constraints including scalar perturbation amplitude.
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Unified Cosmological Scenario in Holographic $f(Q)$ gravity: From Inflation to Late-Time Acceleration
A holographic f(Q) = ζ Q^n model yields slow-roll inflation consistent with Planck 2018 and late-time expansion compatible with CC+BAO data via CPL parametrization, with mild high-z deviations from ΛCDM.
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ACT Data and Positive Running of the Spectral Index for Scalar Theory and Modified Gravity
Einstein-Gauss-Bonnet inflation can yield positive spectral-index running with a viable era under ACT-like hints, while scalar-field and F(R) models largely cannot.
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Reconstructing slow-roll Scalar-Tensor Gauss-Bonnet single field inflation from running spectral data
Derives slow-roll observables and consistency relations for scalar-tensor Gauss-Bonnet inflation and fits a specific model to Planck data.
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String-inspired Gauss-Bonnet Gravity Inflation and ACT
MCMC analysis of sixteen ghost-free f(R,G) inflation models shows all reproduce ns ≈ 0.97 at 60 e-folds with stable μ ≈ 0.1, preference set by Hubble parametrization.
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Inflationary models in a minimally coupled $f(R,T)$ gravity: Constraints from $Planck$, BICEP/$Keck$, and ACT
Three standard inflationary potentials remain compatible with Planck, BICEP/Keck, DESI DR2, and ACT DR6 data when placed in minimally coupled f(R,T)=R+16πGλT gravity for suitable ranges of the model parameters and coupling λ.
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Modified Gravity Theories on a Nutshell: Inflation, Bounce and Late-time Evolution
Modified gravity theories supply viable mathematical frameworks for inflation, bounces, and dark energy eras that match observational data.