Kinetically Modified Palatini Inflation Meets ACT Data

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.