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Lino
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Is the key difference between coasting and static cosmology models the presence of a linear acceleration, or are there other major differences?
Regards,
Noel.
Regards,
Noel.
Lino said:Is the key difference between coasting and static cosmology models the presence of a linear acceleration, or are there other major differences?
Regards,
Noel.
Note that this wouldn't counteract the gravity of matter. Rather, it limits to a coasting cosmology at late times. It only becomes coasting when nearly all of the energy density of the universe is of this kind of stuff. So there's really too much matter in our universe for this model to work.Garth said:A dark energy with an equation of state [itex] \rho = -\frac{1}{3}p[/itex] would achieve this (Kolb's model A coasting cosmology ).
Chalnoth said:Note that this wouldn't counteract the gravity of matter. Rather, it limits to a coasting cosmology at late times. It only becomes coasting when nearly all of the energy density of the universe is of this kind of stuff. So there's really too much matter in our universe for this model to work.
The presence of any matter or electromagnetic energy in the universe would
force the solution of Equation (206) to assume Case 2:
[itex]\sigma = − \frac{1}{3} [/itex] Equation(213)
I'm not sure of any that have investigated this specifically, but this seems to me to be a good way of examining the issue:Lino said:Thanks Chalnoth. Could you recommend any search words or links that are critical of a coasting cosmology (everything I read seems to be very positive)?
Regards,
Noel.
Right. But that's an unstable situation. It may have that density relationship for a short time when the universe transitions from decelerating to accelerating, but it won't stay there.Garth said:If the dark energy itself had an eos of [itex] \rho = -p[/itex], as with the cosmological constant, then [itex] \rho_\Lambda = \frac{1}{3}\rho_M[/itex].
I guess I just have no interest in examining such exotic cosmologies in detail until they can demonstrate that they predict the power spectrum of the CMB (in detail), and in such a way that matches with near-universe estimates of expansion (e.g. BAO, supernova data). These alternative cosmologies are a dime a dozen, and they generally can't be used to predict a CMB power spectrum anything like the one we observe.Garth said:Such an eos is suggested in Self Creation Cosmology (page722)
Coasting cosmology is a theoretical model in which the expansion of the universe remains constant over time, while static cosmology is a model in which the expansion of the universe stops completely and the universe remains the same size. In coasting cosmology, the universe is still expanding, but at a constant rate, while in static cosmology, the universe is not expanding at all.
The Big Bang theory is a widely accepted model for the origin and expansion of the universe, while coasting and static cosmology are alternative theories. The Big Bang theory suggests that the universe began with a rapid expansion from a singularity, while coasting and static cosmology propose different mechanisms for the expansion of the universe.
At this time, there is no observational evidence to support coasting or static cosmology. The majority of evidence, including the cosmic microwave background radiation and the observed acceleration of the universe, supports the Big Bang theory and the current understanding of the expanding universe.
In coasting cosmology, the universe is predicted to expand indefinitely at a constant rate, while in static cosmology, the universe is predicted to eventually collapse in on itself. Both of these theories differ from the Big Bang theory, which predicts that the universe will continue to expand at an accelerating rate.
Scientists use a variety of observational and theoretical tools to test and evaluate different cosmological models, including coasting and static cosmology. These may include analyzing data from telescopes and other instruments, running simulations and experiments, and comparing the predictions of the models to observed phenomena. Ultimately, the validity of a cosmological model is determined by its ability to explain and accurately predict observable phenomena in the universe.