Speaker
Description
We study the energy transfer after inflation from the inflaton ($\phi$) into a scalar field ($\chi$) non-minimally coupled to gravity via $\xi R|\chi|^2$, considering single field inflationary models with potential $\propto |\phi|^{p}$ around $\phi = 0$. This corresponds to the paradigm of geometric preheating, which we extend to its non linear regime by means of lattice simulations. Using $\alpha$-attractor T-model potentials as a proxy, we study the dynamics of the system for $p=2, 4, 6$, and determine whether energetic dominance of $\chi$ over $\phi$ (i.e.~proper reheating) can be achieved, depending on the inflationary energy scale $\Lambda$. While reheating is frustrated for $p = 2$, it can be partially achieved for $p = 4$, and it becomes very efficient for $p = 6$. In the latter case we determine the energy and time scales of reheating as a function of $\xi$ and $\Lambda$, and highlight that contrary to other scenarios, the uncovered mechanism enables full reheating via non-perturbative particle production at arbitrarily low energy scales. Furthermore, we point out that due to the non-linear dynamics, a large gravitational wave background is to be expected, peaked at frequencies accessible to current/planned detectors for sufficiently low $\Lambda$.
