Steady state state model consistent with Big Bang

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SUMMARY

The discussion presents a simple cosmological model defined by the scale factor equation a(t) = A * (exp(H t) - 1), where H^2 = (8 Pi G / 3) rho_min. This model transitions from a linear expansion with a deceleration parameter q = 0 to a steady state Universe with accelerating expansion characterized by q = -1, aligning with Fred Hoyle's theory. The model predicts a dark energy density three times that of matter density, consistent with current cosmological consensus, and avoids singularities at t = 0, implying zero entropy at that point, thus adhering to the second law of thermodynamics.

PREREQUISITES
  • Understanding of Friedmann equations in cosmology
  • Familiarity with concepts of scale factors and expansion in cosmology
  • Knowledge of equations of state in relation to pressure and density
  • Basic grasp of dark energy and its implications in the Universe
NEXT STEPS
  • Study the Friedmann equations with spatial curvature k=0 and cosmological constant=0
  • Explore the implications of the equation of state p = - rho c^2 (3 - 2 exp(-H t)) / 3
  • Investigate the relationship between dark energy density and matter density in cosmological models
  • Examine the Milne model and its relevance to modern cosmological theories
USEFUL FOR

Astronomers, cosmologists, and theoretical physicists interested in alternative cosmological models and the implications of steady state theories in the context of the Big Bang.

johne1618
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The model I have is very simple it is:

a(t) = A * (exp(H t) - 1)

where H^2 = (8 Pi G /3 ) rho_min

and A is just a factor to make a = 1 at the present time t_0:

A = 1 / exp(H t_0 - 1)

and rho_min is the limiting density of matter in the Universe for large t.

The model starts off linear with q = 0, like Milne's massless model, and then quickly tends to Fred Hoyle's steady state Universe with an accelerating expansion q = -1, a constant Hubble radius and continuous matter generation. The equation for the deceleration parameter q = -1 + exp(-H t). It has no cosmological constant but it has an equation of state:


Pressure = - density c^2 (3 - 2 exp(-H t)) / 3

As t -> 0: Pressure = - density c^2 / 3

As t -> infinity: Pressure = - density c^2

For large t we have the second equation of state. As the pressure is multiplied by three in the Friedman acceleration equation:

a'' / a = - 4 Pi G / 3 (rho + 3 p / c^2),

this means that this model predicts that the "dark energy" density should be 3 times the matter density which is consistent with the current consensus.

The problem with Hoyle's steady state was that it was not consistent with the cosmic microwave background and the Big Bang.

However my model does describe a point of infinite mass density as t approaches zero. Interestingly as t->0 the equation of state becomes:

pressure = - density c^2 / 3

This imples the space-time curvature a'' / a -> 0 so there is no singularity at t = 0. The model behaves like the Milne model as t -> 0! I think this is better than the standard big bang model. Having no singularity implies the entropy at t = 0 is zero. This is consistent with the 2nd law of thermodynamics and the arrow of time.
 
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johne1618 said:
The model I have is very simple it is:

a(t) = A * (exp(H t) - 1)

...
Just wondering if you could show the basic Friedmann equation and how you modeled the terms to arrive at this solution of the scale factor?
 
edgepflow said:
Just wondering if you could show the basic Friedmann equation and how you modeled the terms to arrive at this solution of the scale factor?

I start from the Friedmann equations with spatial curvature k=0 and cosmological constant=0:

(a' / a)^2 = 8 Pi G rho / 3

2 a'' / a + (a' / a)^2 = -8 Pi G p / c^2

where rho is the matter density and p is the pressure.

If you substitute my scale factor equation:

a(t) = A (exp(H t) - 1)

where H and A are constants

into the Friedmann equations then you get a solution to them provided the following equation of state holds:

p = - rho c^2 (3 - 2 exp(-H t)) / 3.
 

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