A corollary to the big bang is how the universe will end. One of the mechanisms being suggested results in what is called the Big Rip. It is based on one of the explanations of Dark Enargy, which we know to be 70% of the total energy of the universe.
There are now 4 explanations compatible with observations of Dark Energy: a positive cosmological constant, as predicted by Loop Quantum Gravity; the quintessence field; a Chaplygin gas; and a tachyon model.
The most likely version of the various quintessence models is one that allows the so-called phantom energy in which wormholes and ringholes are allowed. These models predict that phantom energy will someday lead to a doomsday for the universe- a big rip singularity. The stuff making up phantom energy, according to the recent paper cited below, is a vacuum sea of cosmic axions as predicted in string and supergravity theories.
Most previous papers on cosmic axions have considered them to be minutely massive and a constituent of dark matter. I have used them as a basis for a dark matter model of non-local consciousness. But in the paper below they are thought to be the make up of a massless scalar field that mathematically can be pure imaginary, like time in General Rekativety. A quote from the paper:
"It is worth noticing that whereas relic axions are an excellant candidate for the dark matter in the universe, their vacuum quantum background could make cosmic phantom energy"
The paper presents a model which contains a constant omega relating axion pressure to ite density. If omega is positive the universe will just expand forever at an accelerating rate and the massless axion scalar field is real. But if it is negative, phantom enegy results, and the universe will undergo inflation, like what is thought to happen in the big bang, and galaxies and stars and planets will be ripped apart. The negative sign yields an imaginary component to the scalar field which has the singularity in a finite time from now.
The paper does not predict when the big rip will occur except to suggest that based on observations of dark energy, we are already within the onset of phantom energy. The paper does allow that at sufficiently high dark energy, the axion field may decay into gravitons. So if the universe does not exactly rip apart, afterall singularities do not really happen in nature, the universe will at least be "all shook up".
Here is the abstract and the link to the PDF file of the entire paper, which is only 6 pages long:
Axion Phantom Energy
Authors: Pedro F. Gonzalez-Diaz (IMAFF, CSIC, Madrid)
Comments: 6 pages, RevTex, to appear in Phys. Rev. D
The existence of phantom energy in a universe which evolves to eventually show a big rip doomsday is a possibility which is not excluded by present observational constraints. In this letter it is argued that the field theory associated with a simple quintessence model is compatible with a field definition which is interpretable in terms of a rank-three axionic tensor field, whenever we consider a perfect-fluid equation of state that corresponds to the phantom energy regime. Explicit expressions for the axionic field and its potential, both in terms of an imaginary scalar field, are derived which show that these quantities both diverge at the big rip, and that the onset of phantom-energy dominance must take place just at present.
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