2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/201959It is well known that there should be a total cancellation of the IR divergences in unitary interacting field theories, such as QED and gravity. The cancellation should be at all orders between loop and tree level contributions to cross--sections. This is the crucial fact related to the unitarity of the evolution operator (S--matrix) of the underlying interacting field theory. In this note we show that such a cancellation does {\it not} happen in de Sitter space.10 pages RevTeX, 1 figure. Additional arguments are given, statements are made more preciseHigh Energy Physics - TheoryGeneral Relativity and Quantum CosmologyHigh Energy Physics - Phenomenologytext