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arxiv: 1008.0603 · v3 · pith:LCRGEEYNnew · submitted 2010-08-03 · ✦ hep-th · astro-ph.CO· gr-qc

G-inflation: inflation driven by the Galileon field

classification ✦ hep-th astro-ph.COgr-qc
keywords inflationexperimentsg-inflationstandardalmostbackgroundblueclass
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We propose a new class of inflation model, G-inflation, which has a Galileon-like nonlinear derivative interaction of the form $G(\phi, (\nabla\phi)^2)\Box\phi$ in the Lagrangian with the resultant equations of motion being of second order. It is shown that (almost) scale-invariant curvature fluctuations can be generated even in the exactly de Sitter background and that the tensor-to-scalar ratio can take a significantly larger value than in the standard inflation models, violating the standard consistency relation. Furthermore, violation of the null energy condition can occur without any instabilities. As a result, the spectral index of tensor modes can be blue, which makes it easier to observe quantum gravitational waves from inflation by the planned gravitational-wave experiments such as LISA and DECIGO as well as by the upcoming CMB experiments such as Planck and CMBpol.

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Cited by 4 Pith papers

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  1. How deep can a cosmic void be? Voids-informed theoretical bounds in Galileon gravity

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    Galileon models must obey a void-depth limit tied to expansion history to avoid force breakdowns, excluding ~60% of a linear parameterization's space by z less than or equal to 10.

  2. Constraints on the inflationary vacuum and reheating era from NANOGrav

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    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.

  3. Nonthermal leptogenesis via cosmological gravitational particle production is tested by inflationary gravitational waves

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    Certain inflation models produce right-handed neutrinos via gravitational effects sufficient for leptogenesis to explain the baryon asymmetry, testable by inflationary gravitational waves.

  4. Reviving Motivated Inflationary Potentials with $K$-inflation in the light of ACT

    gr-qc 2026-05 unverdicted novelty 5.0

    K-inflation with non-canonical kinetic term G(φ) shifts α-attractor T-models and natural inflation into the Planck-ACT-LB-BK18 allowed region while satisfying Swampland conjectures and producing testable GW spectra.