Curvature-induced phantom behavior and cosmological bounces without violating the Dominant Energy Condition

Abstract

We show that a spatially closed universe can exhibit effective phantom dynamics ($q<-1$) and reach a finite-time cosmological event without violating the Dominant Energy Condition (DEC). Whereas the standard Big Rip is driven by a phantom fluid that breaks the energy conditions, here non-null spatial curvature acts as an active geometric contributor: for matter that strictly obeys the DEC ($ω\ge-1$), positive spatial curvature by itself drives the deceleration parameter to values below $-1$ and brings the expansion to a stop at a finite value of the scale factor, where the Hubble parameter vanishes while the energy density stays finite. Since the curvature also keeps the Hubble radius regular at this point, the event is naturally interpreted as a cosmological bounce rather than a disruptive singularity. We contrast this DEC-preserving mechanism with the genuine phantom case ($ω<-1$), for which the same closed geometry produces an early bounce followed by a late Big Rip, and we comment on the observational status of the curvature contribution.