Kinetically Modified Palatini Inflation Meets ACT Data

TL;DR

This paper proposes a modified Palatini inflation model with non-minimal coupling and kinetic mixing that aligns with ACT data, allowing for subplanckian inflationary scales and embedding in supergravity.

Contribution

It introduces a kinetically modified Palatini inflation model with specific couplings that reconcile chaotic inflation with recent observational data, and demonstrates its supergravity embedding.

Findings

Reconciles chaotic inflation with ACT data using Palatini formulation.

Allows for subplanckian inflaton values and energy scales.

Can be embedded in supergravity with specific superpotential and Kähler potential.

Abstract

We show that the coexistence of a non-minimal coupling to gravity $f_{\mathcal{R}}=1+c{\mathcal{R}} \phi^{n/2}$ with a kinetic mixing of the form $f_K = f_{\mathcal{R}}^m$ -- where $n=2$ and 4 and $0.5 \le m \le 10$ -- reconciles chaotic inflation based on the $\phi^n$ potential with the recent ACT results, if we adopt the Palatini formulation of gravity. The attainment of inflation allows for subplanckian inflaton values and energy scales below the cut-off scale of the corresponding effective theory. The model can be also embedded in supergravity by introducing two chiral superfields and a monomial superpotential, linear with respect to the inflaton-accompanying field. Its stabilization is achieved thanks to a compact contribution to the Kaehler potential, whose the inflationary part includes an holomorphic logarithmic term and a real one multiplying a shift-symmetric quadratic polynomial term.