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}
}
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… 

Figures and Tables from this paper

Explicit Integration of Friedmann's Equation with Nonlinear Equations of State
This paper is a continuation of our earlier study on the integrability of the Friedmann equations in the light of the Chebyshev theorem. Our main focus will be on a series of important, yet not
Wheeler--DeWitt Universe Wave Function in the Presence of Stiff Matter
We study the Wheeler-DeWitt (WDW) equation close to the Big-Bang. We argue that an interaction dominated fluid (speed of sound equal to the speed of light), if present, would dominate during such an
Creation of Matter in a Noncommutative Universe
The dark matter and dark energy problem, that is now dominating the research in cosmology, makes the question of the origin of mass-energy content of the universe more urgent than ever. There are two
Nonlocal modified Einstein’s field equation and geometric origin of a small cosmological constant
Abstract.We show that the description of the spacetime in terms of backward-forward extension of its corresponding metric leads to the geometric origin of a small cosmological constant. The nonlocal
A higher dimensional cosmological model for the search of dark energy source
With due consideration of reasonable cosmological assumptions within the limit of the present cosmological scenario, we have analyzed a spherically symmetric metric in 5D setting within the framework
Evolution of Density Parameters on a Smooth Embedded Universe
In this paper we examine the evolution of cosmic density parameters in a four‐dimensional space‐time embedded in a five‐dimensional bulk space. We show that the extrinsic curvature is an independent
Higher-order gravity in higher dimensions: geometrical origins of four-dimensional cosmology?
Determining the cosmological field equations is still very much debated and led to a wide discussion around different theoretical proposals. A suitable conceptual scheme could be represented by
Constraints on $$\sigma _8$$ σ 8 and degeneracies from linear Nash-Greene perturbations in subhorizon scale
Using a joint statistical analysis, we test a four-dimensional FLRW model embedded in a five-dimensional bulk based on the Nash-Greene embedding theorem. Performing a Markov Chain Monte Carlo (MCMC)
...
...

References

SHOWING 1-10 OF 67 REFERENCES
Quantum Inequality Restrictions on Negative Energy Densities in Curved Spacetimes
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.
  • Ford, Román
  • Physics
    Physical review. D, Particles and fields
  • 1996
TLDR
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?
TLDR
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
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
...
...