# No open or flat bouncing cosmologies in Einstein gravity

@article{Parikh2015NoOO, title={No open or flat bouncing cosmologies in Einstein gravity}, author={Maulik Parikh}, journal={Journal of High Energy Physics}, year={2015}, volume={2015}, pages={1-11} }

A bstractWe show that, to first approximation, strings cannot propagate in bouncing open or flat Friedmann-Robertson-Walker universes. Specifically, the Virasoro constraint translates to the Ricci convergence condition in spacetime at leading order in the alpha-prime expansion. Thus one must go beyond minimally-coupled classical Einstein gravity in order to find bounce solutions that could be consistent with string theory. We map out some remaining possibilities for finding string-compatible…

## 7 Citations

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It is argued that the heterotic string does not have classical vacua corresponding to de Sitter space-times of dimension four or higher, and suggests that the genericity arguments used in string landscape discussions should be viewed with caution.

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The null energy condition has sweeping consequences in general relativity. I argue here that it has been misunderstood as a property exclusively of matter, when in fact it arises only in a theory of…

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The null energy condition has sweeping consequences in general relativity. I argue here that it has been misunderstood as a property exclusively of matter, when in fact it arises only in a theory of…

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Here I develop the connection between thermodynamics, entanglement, and gravity. I begin by showing that the classical null energy condition (NEC) can arise as a consequence of the second law of…

### Thermodynamic Origin of the Null Energy Condition

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- 2017

We derive the classical null energy condition, understood as a constraint on the Ricci tensor, from the second law of thermodynamics applied locally to Bekenstein-Hawking entropy associated with…

## References

SHOWING 1-10 OF 33 REFERENCES

### Cosmological super-bounce

- Physics
- 2014

We study a model for a non-singular cosmic bounce in N=1 supergravity, based on supergravity versions of the ghost condensate and cubic Galileon scalar field theories. The bounce is preceded by an…

### Bouncing cosmologies in massive gravity on de Sitter

- Physics
- 2013

In the framework of massive gravity with a de Sitter reference metric, we study homogeneous and isotropic solutions with positive spatial curvature. Remarkably, we find that bounces can occur when…

### G-bounce

- Physics
- 2011

We present a wide class of models which realise a bounce in a spatially flat Friedmann universe in standard General Relativity. The key ingredient of the theories we consider is a noncanonical,…

### Bouncing universe with Quintom matter

- Physics
- 2007

The bouncing universe provides a possible solution to the Big Bang singularity problem. In this paper we study the bouncing solution in the universe dominated by the Quintom matter with an equation…

### Matter bounce cosmology with the f(T) gravity

- Physics
- 2011

We show that the f(T) gravitational paradigm, in which gravity is described by an arbitrary function of the torsion scalar, can provide a mechanism for realizing bouncing cosmologies, thereby…

### Bouncing Galileon cosmologies

- Physics
- 2011

We present nonsingular, homogeneous and isotropic bouncing solutions of the conformal Galileon model. We show that such solutions necessarily begin with a radiation-dominated contracting phase. This…

### A Matter Bounce By Means of Ghost Condensation

- Physics
- 2010

Assuming the existence of a scalar field which undergoes "ghost condensation" and which has a suitably chosen potential, it is possible to obtain a non-singular bouncing cosmology in the presence of…

### Bouncing universes in string-inspired gravity

- Physics
- 2006

We consider the effects on cosmology of higher derivative modifications of gravity that make it asymptotically free without introducing ghosts. The weakening of gravity at short distances allows…

### Constraints on string cosmology

- PhysicsClassical and Quantum Gravity
- 2012

String theory contains sources like orientifold planes that support higher derivative interactions. These interactions make static flux compactifications possible which are forbidden in supergravity.…