# An exposition on Friedmann cosmology with negative energy densities

@article{Nemiroff2015AnEO,
title={An exposition on Friedmann cosmology with negative energy densities},
author={Robert J. Nemiroff and Ravi Joshi and Bijunath R. Patla},
journal={Journal of Cosmology and Astroparticle Physics},
year={2015},
volume={2015},
pages={006-006}
}
• Published 18 February 2014
• Physics
• Journal of Cosmology and Astroparticle Physics
How would negative energy density affect a classic Friedmann cosmology? Although never measured and possibly unphysical, certain realizations of quantum field theories leaves the door open for such a possibility. In this paper we analyze the evolution of a universe comprising varying amounts of negative energy forms. Negative energy components have negative normalized energy densities, Ω 1/3. Assuming that such energy forms generate pressure like perfect fluids, the attractive or repulsive…
21 Citations

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## References

SHOWING 1-10 OF 67 REFERENCES
Quantum Inequality Restrictions on Negative Energy Densities in Curved Spacetimes
• Physics
• 1998
In quantum field theory, there exist states in which the expectation value of the energy density for a quantized field is negative. These negative energy densities lead to several problems such as
Quantum field theory constrains traversable wormhole geometries.
• Physics
Physical review. D, Particles and fields
• 1996
This work applies an uncertainty-principle-type bound on negative energy densities in four-dimensional Minkowski spacetime to the stress-energy of static traversable wormhole spacetimes and implies that either the wormhole must be only a little larger than Planck size or that there is a large discrepancy in the length scales which characterize the wormholes.
'Operational' energy conditions
The negative energy densities predicted by relativistic quantum field theories are investigated. Combining the quantum inequalities of Ford and Roman, which restrict the time for which a negative
The cosmological constant problem and quintessence
I briefly review the cosmological constant problem and the issue of dark energy (or quintessence). Within the framework of quantum field theory, the vacuum expectation value of the energy momentum
Quintessence, cosmic coincidence, and the cosmological constant
Recent observations suggest that a large fraction of the energy density of the Universe has negative pressure. One explanation is vacuum energy density; another is quintessence in the form of a
Thermal relics: Do we know their abundances?
• Physics
Physical review. D, Particles and fields
• 1990
Three nonstandard possibilities for the Universe at the time a species’ abundance froze in are considered: energy density dominated by shear, energy density dominance of the scalar field that sets the gravitational constant in a Brans-Dicke-Jordan cosmological model, and a component of the energy density at early times with a very stiff equation of state.
Inflationary universe: A possible solution to the horizon and flatness problems
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
PROBING DARK ENERGY: METHODS AND STRATEGIES
• Physics
• 2001
The presence of dark energy in the Universe is inferred directly from the accelerated expansion of the Universe, and indirectly, from measurements of cosmic microwave background (CMB) anisotropy.
Gravitation and cosmology with York time
[Shortened abstract:] In this thesis we investigate a solution to the `problem of time' in canonical quantum gravity by splitting spacetime into surfaces of constant mean curvature parameterised by