  We make use of classical lattice simulations in 3 + 1 dimensions to study the
preheating stage of Higgs Inflation in Einstein-Cartan gravity. Focusing for
concreteness on a simplified scenario involving the seminal Nieh-Yan term, we
demonstrate the formation of dense and spatially localized oscillon
configurations constituting up to 70% of the total energy density. The
emergence of these meta-stable objects may lead to a prolonged period of matter
domination, effectively modifying the post-inflationary history of the Universe
as compared to the metric and Palatini counterparts. Notably, the creation of
oscillons comes together with a significant gravitational wave signal, whose
typical frequency lies, however, beyond the range accessible by existing and
planned gravitational wave experiments. The impact of the Standard Model gauge
bosons and fermions and the potential extension of our results to more general
Einstein-Cartan settings is also discussed.
