Bayesian Analysis Favors Quartic Potential in Low-Temperature Warm Inflation Models
A new arXiv preprint applies Bayesian model comparison to rank monomial inflation potentials in the warm inflation framework, finding strong statistical preference for the quartic potential (p=4) over quadratic and cubic alternatives. Cold single-field inflation models with these potentials face tension with observational limits on the tensor-to-scalar ratio, and warm inflation offers a mechanism to relieve that tension by boosting the scalar power spectrum. The result matters because it narrows the theoretical landscape of viable inflationary models and identifies a specific physical mechanism—Bose-Einstein occupation enhancement—as the key driver of the quartic potential's advantage.
Researchers have performed an effective Bayesian evidence ranking of monomial scalar field potentials of the form V_p(φ) = λ_p φ^p / p, for p = 2, 3, and 4, within the low-temperature warm inflation scenario using a dissipative coefficient fixed as Υ = C_φ T³/φ². In standard cold single-field slow-roll inflation, all three potentials are strongly constrained by the observational upper bound on the tensor-to-scalar ratio r, but warm inflation can alleviate this tension by enhancing the scalar perturbation spectrum. The study integrates a compressed likelihood over the observables (A_s, n_s, r_{0.05}) and the viable prior volume for each potential branch, yielding log-evidence differences of Δln Z = −32.18 for the quadratic and −6.99 for the cubic relative to the quartic. A representative quartic trajectory produces n_s = 0.9642 and r_{0.05} = 0.0266, consistent with current CMB observations, in a weakly dissipative but thermally occupied regime where T*/H* ≈ 10.67. Spectral decomposition reveals that the quartic potential's statistical advantage is driven primarily by Bose-Einstein occupation enhancement when T*/H* > 1, rather than by strong dissipative friction. The evidence hierarchy p=4 > p=3 >> p=2 is reported to be robust across variations in the number of e-folds N*, prior ranges, random seeds, and treatment of the r bound. The work is a preprint submitted to arXiv and has not yet undergone formal peer review.
What's missing
The study's own key limitations include: (1) the dissipative coefficient form Υ = C_φ T³/φ² is fixed by assumption rather than derived from a specific microphysical model, so results may not generalize to other dissipation prescriptions; (2) the Bayesian evidence is labeled 'effective' because it uses a compressed, broadened likelihood rather than a full CMB likelihood, which may not capture all observational correlations; (3) the analysis is restricted to the low-temperature warm inflation regime and does not address the high-temperature branch; (4) the prior choices, while tested for stability, are not derived from first principles and could influence the evidence ratios.
What different sources said
- arXiv astro-phCenter
Effective Bayesian ranking of low order monomial potentials in low temperature warm inflation
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