Inflation in light of ACT/SPT: A new perspective from Weyl gravity

Abstract

Recent measurements from the Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT) have placed the strictest constraints on the primordial scalar perturbation spectrum, reporting a spectral index of $n_s\sim 0.967-0.98$ at 95% confidence level. This result indicates a stronger scale invariance of the scalar perturbation than earlier estimates, posing challenges for numerous inflation models. In this work, we propose a novel inflationary scenario based on Weyl scale-invariant gravity, where the quadratic curvature establishes the scale invariance of the scalar spectrum, while the higher-order extensions imprint the observed slight deviation. Specifically, the exponential curvature extensions are introduced to suppress the mass divergence of the inflaton. We find such scenario naturally yields leading-order predictions of $n_s\simeq 1-3/(2N)\sim 0.97-0.975$ or $n_s\simeq 1-5/(3N)\sim 0.967-0.972$ for various models, in excellent agreement with the ACT/SPT constraints. This result builds a concrete bridge between theoretical and observational scale invariance, implying an enduring cosmic echo of the primordial symmetry.

7 pages, 2 figures

References in corpus (22)

• The Standard Model Higgs boson as the inflaton
• DESI DR2 Results II: Measurements of Baryon Acoustic Oscillations and Cosmological Constraints
• Gravitational production of vector dark matter
• Weyl Current, Scale-Invariant Inflation and Planck Scale Generation
• Gauging scale symmetry and inflation: Weyl versus Palatini gravity
• Analytic extensions of Starobinsky model of inflation
• SPT-3G D1: CMB temperature and polarization power spectra and cosmology from 2019 and 2020 observations of the SPT-3G Main field
• Keeping the relation between the Starobinsky model and no-scale supergravity ACTive
• Dark matter as a Weyl geometric effect
• Implication of Compensator Field and Local Scale Invariance in the Standard Model
• Quasinormal Ringing and Shadows of Black Holes and Wormholes in Dark Matter-Inspired Weyl Gravity
• Weyl type $f(Q,T)$ gravity observational constrained cosmological model
• Weyl Scaling Invariant $R^2$ Gravity for Inflation and Dark Matter
• Inflation in Weyl-invariant Einstein-Cartan gravity
• Tabletop potentials for inflation from $f(R)$ gravity
• Cosmological implications of the Weyl geometric gravity theory
• Cornering Extended Starobinsky Inflation with CMB and SKA
• Dark Matter Production in Weyl $R^2$ Inflation
• Inflation in Weyl Scaling Invariant Gravity with $R^3$ Extensions
• Gravitational Waves from Preheating in Inflation with Weyl Symmetry
• Higgs Potential from Weyl Conformal Gravity
• Cosmic inflation from broken conformal symmetry