A halfway ending. Some structures are torn apart, the most tightly bound survive.
The Pseudo-Rip
An intermediate future where the expansion rate rises toward a finite ceiling, so the dark energy unbinds loosely held structures but leaves the most tightly bound ones intact.
Looping ambient scene for Rip Scenarios. The rip futures all follow from phantom dark energy: a dark energy whose density increases as the universe expands, which happens when its equation of state w sits below -1. A growing repulsion does not just accelerate the expansion, it strengthens without limit, so structures held together by gravity, then by electromagnetism, then by the nuclear forces, are progressively unbound. The variants differ in how the energy density grows and therefore in whether the end comes at a finite time (the Big Rip), only as time runs to infinity (the Little Rip), or in an intermediate way that spares some structures (the Pseudo-Rip and the Little Sibling of the Big Rip). All of them rest on the premise that w is below -1, which current data neither confirm nor exclude.
§1 · The claim, in one sentence
The Pseudo-Rip sits between heat death and the rips. Here the Hubble expansion rate rises but approaches a finite constant rather than diverging, so the disruptive inertial force grows to a ceiling instead of to infinity. Frampton, Ludwick, and Scherrer 2012 showed that such a future dissolves weakly bound systems, like galaxy clusters and perhaps galaxies, while leaving tightly bound systems, like the Solar System or atoms, intact.
§2 · Why it might be true
Both the Big Rip and the Little Rip drive the disruptive force on bound systems to infinity, so everything eventually comes apart. The Pseudo-Rip asks what happens if that force grows but levels off at a finite value.
In this case the universe still ends in eternal accelerating expansion, asymptotically approaching a de Sitter-like state. The difference is that during the approach the dark energy gets strong enough to tear apart loosely bound structures but never strong enough to overcome the tighter ones. Which systems survive depends on the height of the ceiling relative to each structure's binding energy.
The Pseudo-Rip thus blurs the line between the rip futures and an eternal freeze. It is a reminder that the fate of the universe is not a simple binary between tearing apart and fading away. A continuum of dark energy behaviours produces a continuum of endings, and the Pseudo-Rip occupies the middle of that range.
The family stance
The universe ends by being torn apart. A dark energy that grows stronger over time eventually overwhelms gravity and every other force, dismantling bound structures from the largest scales down to atoms. Whether this happens at a finite future moment or only asymptotically depends on exactly how the dark energy density grows.
§2.5 · Evidence
- It removes both the finite-time singularity of the Big Rip and the unbounded growth of the Little Rip, so it is the most theoretically conservative member of the rip family
- It connects smoothly to the heat-death future in the limit where the ceiling is low, so it is not a sharp departure from the standard picture
- It remains within the dynamical-dark-energy parameter space that current data allow
§3 · What you'd need to test it
- The Hubble rate rises toward a finite asymptotic value rather than diverging
- Loosely bound structures (clusters, possibly galaxies) are unbound while tightly bound systems survive intact
- The universe still ends in eternal acceleration, approaching a de Sitter-like state, so this is a hybrid of rip and freeze
- The dividing line between dissolved and surviving structures is set by the asymptotic expansion rate, a single number future surveys could in principle constrain
§4 · Where it breaks
- It is the least distinctive rip scenario, shading into ordinary eternal acceleration, so its status as a separate fate is partly a matter of definition
- It still requires dark energy that strengthens over time, beyond a simple cosmological constant, with no positive evidence that this occurs
- Its observational signature is even subtler than the Little Rip's, making it hard to confirm
Go deeper
Frampton, Ludwick, and Scherrer 2012 (Phys. Rev. D 85, 083001) define the Pseudo-Rip by a Hubble rate that increases monotonically toward a finite limit. The inertial force on a two-body system depends on the Hubble rate and its derivative, so a bounded Hubble rate gives a bounded maximum force. Systems with binding stronger than that maximum survive forever; weaker ones are torn apart at a calculable time. This produces a layered outcome rather than total dissolution.
Placed alongside its siblings, the Pseudo-Rip completes a clean classification of phantom-like futures by the asymptotic behaviour of the Hubble rate: divergent in finite time gives the Big Rip, divergent at infinite time gives the Little Rip, and convergent to a finite value gives the Pseudo-Rip. The cosmological-constant case, with a constant Hubble rate from the start, is the heat-death limit of the same family.
Cross-references: see the Big Rip and Little Rip variants in this family for the more destructive limits, and the Heat Death and Eternal Expansion family for the freeze limit this scenario approaches when its force ceiling is low.
Variants in this family
Compare variants▸§5 · Who built it, and when(1 source, 1 established)
Up next
Spotted an error? Have a source to add?
Prefer email?
You can also send a prefilled email with the variant URL already filled in.