Is the cosmological particle creation adequately described by an asymptotic in-out calculation

The aim of this letter is to demonstrate that asymptotic in-out calculations, although correct from a formal mathematical point of view, have in return little or nothing to do with the physical situation and the expected outcome of a cosmological gravitational particle creation, if this creation is supposed to be appropriately localized in time and atributed to the occurrence of strong gravitational fields (curvature). To demonstrate this, the example of a universe with an expansion-contraction behaviour is treated rigorously, showing temporarily arbitrarily strong gravitational fields (high tidal forces, large curvature), which nevertheless in an in-out calculation exactly no particles. In other words, according to an in-out calculation this universe 'works and works and produces nothing'. (Auth.)