Warm inflation tested inside an alternative geometric gravity theory

Working within Weyl geometric gravity — a conformally invariant framework that promotes the metric connection to carry an extra vector field — the authors reformulate an R̃² action as a scalar-tensor theory and study warm inflation, where the inflaton continuously dissipates energy into radiation throughout the inflationary epoch. Using a quartic potential and a linear dissipation coefficient, numerical solutions show the Universe exits inflation directly into a radiation-dominated phase without a separate reheating stage. The predicted spectral index and tensor-to-scalar ratio are compared against ACT data, with the Weyl vector coupling serving as a distinguishing parameter.