Palatini $F(R,X)$: a new framework for inflationary attractors

Abstract

Palatini $F(R)$ gravity proved to be a powerful tool in order to realize asymptotically flat inflaton potentials. Unfortunately, it also inevitably implies higher-order inflaton kinetic terms in the Einstein frame that might jeopardize the evolution of the system out of the slow-roll regime. We prove that a $F(R+X)$ gravity, where $X$ is the inflaton kinetic term, solves the issue. Moreover, when $F$ is a quadratic function such a choice easily leads to a new class of inflationary attractors, fractional attractors, that generalizes the already well-known polynomial $\alpha$-attractors.

11 pages, 5 figures, major changes in section 2 and 3, added new appendix A and B. Matches the published version

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Cited by in corpus (9)

• Fractional attractors in light of the latest ACT observations
• Approximate reconstruction of inflationary potential with ACT observations
• Inflation and reheating in quadratic metric-affine gravity with derivative couplings
• General Einstein-Cartan quadratic gravity with derivative couplings
• $\tilde{\xi }$-attractors in metric-affine gravity
• Natural inflation in Palatini $F(R,X)$
• Natural inflation in Palatini $F(R)$
• Quintessential Inflation in Palatini $F(R,X)$ gravity
• Inflation with the Gauss-Bonnet term in the Palatini formulation