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Cosmology: Equation of state parameter

  • Thread starter Niles
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Homework Statement


Hi all.

The pressure in a multi-component universe is additive, just as the energy-density is:

[tex]
P = \sum\limits_i {w_i \varepsilon _i } \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\rm{and}}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\varepsilon = \sum\limits_i {\varepsilon _i }
[/tex]

But what about w? In the Benchmark-model is w = 0 + (-1) = -1 (we approximate to matter and Lambda), or is it a weighted average, i.e. 0.3 * 0 + 0.7*(-1) = -0.7?
 

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