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Analytic extensions of Starobinsky model of inflation

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arxiv 2111.09058 v3 pith:BBXG4A5A submitted 2021-11-17 gr-qc astro-ph.COhep-th

Vsevolod R. Ivanov , Sergei V. Ketov , Ekaterina O. Pozdeeva , Sergey Yu. Vernov This is my paper
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keywords modelstarobinskyparameterstermframeinflationscalarcalculate
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abstract

We study several extensions of the Starobinsky model of inflation, which obey all observational constraints on the inflationary parameters, by demanding that both the inflaton scalar potential in the Einstein frame and the $F(R)$ gravity function in the Jordan frame have the explicit dependence upon fields {\it and} parameters in terms of elementary functions. Our models are continuously connected to the original Starobinsky model via changing the parameters. We modify the Starobinsky $(R+R^2)$ model by adding an $R^3$-term, an $R^4$-term, and an $R^{3/2}$-term, respectively, and calculate the scalar potentials, the inflationary observables and the allowed limits on the deformation parameters by using the latest observational bounds. We find that the tensor-to-scalar ratio in the Starobinsky model modified by the $R^{3/2}$-term significantly increases with raising the parameter in front of that term. On the other side, we deform the scalar potential of the Starobinsky model in the Einstein frame in powers of $y=\exp\left(-\sqrt{\frac{2}{3}}\phi/M_{Pl}\right)$, where $\phi$ is the canonical inflaton (scalaron) field, calculate the corresponding $F(R)$ gravity functions in the two new cases, and find the restrictions on the deformation parameters in the lowest orders with respect to the variable $y$ that is physically small during slow-roll inflation.

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Cited by 5 Pith papers

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

  1. Unstable de Sitter inflationary solution in sixth-order gravity

    gr-qc 2026-07 conditional novelty 6.0 of 10

    For the sixth-order gravity action (2.1), the exact FLRW de Sitter solution is unstable whenever 3γ1+γ2<0, while the second-order limit admits a stable de Sitter attractor.

  2. ACT stands for Awkward Cosmology Theories

    hep-ph 2026-07 accept novelty 6.0 of 10

    Reconciling Starobinsky inflation with ACT data requires fine-tuned higher-curvature scales, stiff reheating with ω_reh>1/3, or negative-energy towers, all hard to motivate from UV completions.

  3. Inflationary assessment of $F(\mathcal{R},\tilde{\mathcal{R}})$ Einstein-Cartan models

    gr-qc 2025-12 conditional novelty 5.0 of 10

    Adding cubic Holst-invariant terms to F(R,R̃) Einstein-Cartan inflation models systematically lowers the predicted spectral index n_s and tensor-to-scalar ratio r, restoring data compatibility in parameter regions whe...

  4. Starobinsky Inflation and the Latest CMB Data: A Subtle Tension?

    astro-ph.CO 2025-11 conditional novelty 4.0 of 10

    When implemented directly in CLASS, Starobinsky inflation remains consistent with Planck+ACT+BAO data at the 2σ level, but the inferred e-fold range sits above the reheating-motivated window, and a fitted R³ correctio...

  5. Investigating $f(R)$-Inflation: background evolution and constraints

    astro-ph.CO 2025-07 conditional novelty 4.0 of 10

    A Jordan-frame f(R) model with particle creation during inflation is fitted to DESI and Pantheon+ data, yielding H0=71.04 and a claimed reduction of the Hubble tension to about 1.6-2.8 sigma.

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