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arxiv 2507.18684 v1 pith:T5ZSICC2 submitted 2025-07-24 astro-ph.CO

Reconciling Fractional Power Potential and EGB Gravity in the light of ACT

classification astro-ph.CO
keywords scalarmodelsresultsbonnetconstraintscosmologicaldatafractional
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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Recent results from the ACT collaboration indicate a higher value for the scalar spectral index, with $n_s = 0.9743 \pm 0.0034$, which sets tighter constraints on inflationary models, and these shifts are not in favor of many pre existing scenarios, including the widely studied and accepted standard Starobinsky model. In this paper, we examine the fractional power scalar potential within the framework of Einstein Gauss Bonnet (EGB) gravity, incorporating standard slow roll approximation. The EGB theory, motivated by higher dimensional models, introduces quadratic curvature corrections and a coupling between the scalar field and the Gauss Bonnet term, thereby modifying the cosmological dynamics. The results show good agreement with observational data, placing the predictions within the $1 \sigma$ region of the ACT $r-n_s$ constraint plot. Furthermore, incorporating the running of the scalar spectral index reinforces the models consistency with observational bounds. We also explore the parameter space of the EGB couplings and identify the range of free parameters for which the results of $n_s$ and $r$ values remain within the $1 \sigma$ region of the ACT constraints. Finally, we also investigate the reheating phase, demonstrating that the model not only agrees with ACT data but also satisfies the lower bound on the reheating temperature, thereby ensuring a consistent and viable cosmological scenario.

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Cited by 6 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Harrison-Zeldovich attractor: From Planck to ACT results

    astro-ph.CO 2025-10 conditional novelty 6.0

    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.

  2. Preheating and oscillon formation in Einstein-scalar-Gauss-Bonnet gravity

    gr-qc 2026-07 unverdicted novelty 5.0

    Simulations in Einstein-scalar-Gauss-Bonnet gravity show oscillons form with similar properties to standard cases but trigger EFT breakdown for large couplings via high local curvatures.

  3. ACT Data and Positive Running of the Spectral Index for Scalar Theory and Modified Gravity

    gr-qc 2026-05 unverdicted novelty 5.0

    Positive running of the spectral index is achievable in Einstein-Gauss-Bonnet gravity with viable inflation, unlike standard scalar field and F(R) models which face challenges.

  4. Starobinsky Inflation in k-Essence Framework: Attractor Dynamics, Reheating, and Consistency with ACT DR6

    gr-qc 2026-07 conditional novelty 4.0

    A power-law non-canonical kinetic coupling F(φ)=1+Aφ^n revives the Starobinsky inflation potential's consistency with ACT DR6 CMB data while preserving attractor dynamics and yielding viable reheating.

  5. Reconstructing ACT-compatible and GW170817-compatible Einstein-Gauss-Bonnet Inflation from the Observational Indices

    gr-qc 2026-05 unverdicted novelty 4.0

    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.

  6. String-inspired Gauss-Bonnet Gravity Inflation and ACT

    gr-qc 2026-04 unverdicted novelty 4.0

    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.