# On the past-completeness of inflationary spacetimes

@inproceedings{Lesnefsky2022OnTP, title={On the past-completeness of inflationary spacetimes}, author={Joseph Lesnefsky and Damien A Easson and Paul C. W. Davies}, year={2022} }

We discuss the question of whether or not inﬂationary spacetimes can be geodesically complete in the inﬁnite past. Geodesic completeness is a necessary condition for averting an initial singularity during eternal inﬂation. It is frequently argued that cosmological models which are expanding suﬃciently fast (having average Hubble expansion rate H avg > 0 ) must be incomplete in null and timelike past directions. This well-known conjecture relies on speciﬁc bounds on the integral of the Hubble…

## References

SHOWING 1-10 OF 54 REFERENCES

### Inflationary spacetimes are incomplete in past directions.

- PhysicsPhysical review letters
- 2003

A simple kinematical argument is offered that a cosmological model which is inflating--or just expanding sufficiently fast--must be incomplete in null and timelike past directions, and a bound on the integral of the Hubble parameter over a past-directed timelikes or null geodesic is obtained.

### A simple harmonic universe

- Physics
- 2011

A bstractWe explore simple but novel bouncing solutions of general relativity that avoid singularities. These solutions require curvature k = +1, and are supported by a negative cosmological term and…

### The Phantom of the New Oscillatory Cosmological Phase

- Physics, Mathematics
- 2016

We study a recently proposed new cosmological phase where a scalar field moves periodically in an expanding spatially-flat Friedmann universe. This phase corresponds to a limiting cycle of the…

### Quantum instability of the emergent universe

- Physics
- 2013

We perform a semi-classical analysis of the Emergent Universe scenario for inflation. Fixing the background, and taking the inflaton to be homogenous, we cast the inflaton’s evolution as a…

### Galilean Genesis: An Alternative to inflation

- Physics
- 2010

We propose a novel cosmological scenario, in which standard inflation is replaced by an expanding phase with a drastic violation of the Null Energy Condition (NEC): >> H2. The model is based on the…

### Oscillatory attractors: a new cosmological phase

- Physics
- 2015

In expanding FRW spacetimes, it is usually the case that homogeneous scalar fields redshift and their amplitudes approach limiting values: Hubble friction usually ensures that the field relaxes to…

### Brane gases in the early Universe

- Physics
- 2000

Over the past decade it has become clear that fundamental strings are not the only fundamental degrees of freedom in string theory. D-branes are also part of the spectrum of fundamental states. In…

### Inflationary universe: A possible solution to the horizon and flatness problems

- Physics
- 1981

The standard model of hot big-bang cosmology requires initial conditions which are problematic in two ways: (1) The early universe is assumed to be highly homogeneous, in spite of the fact that…

### Eternal inflation and its implications

- Economics
- 2007

I summarize the arguments that strongly suggest that our universe is the product of inflation. The mechanisms that lead to eternal inflation in both new and chaotic models are described. Although the…