2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/6879The expansion of spacetime alters the energy-time uncertainty principle, allowing virtual particles to persist longer than in flat space. For a given expansion the effect is largest for massless particles which are not conformally invariant. For a given particle type the effect is largest for inflation. I exhibit these two principles in the context of massless fermions which are Yukawa-coupled to massless scalars. I also review the many related examples which have been studied recently.6 pages, LaTeX2e, Proceedings for the 6th Workshop on QFT under the Influence of External Conditions, Norman, OK, Sept. 15-19, 2003AstrophysicsGeneral Relativity and Quantum CosmologyHigh Energy Physics - Phenomenologytext