The Classical Cosmological Tests Applied to World Models with Pressure
Abstract
We apply the three classical tests of observational cosmology, i.e. the m(z), the φ(z) and the N(z) tests, to world models with pressure and demonstrate that they are degenerate with respect to the pressure parameter α_0_ (= 3 P_0_/ρ_0_ c^2^) in the range 01. This degeneracy is due to the fact that for all redshifts, z, less than ~2 the results of the tests for a given value of the deceleration parameter, qfl, are almost identical for models with different values of all, the differences being very small as compared to observational uncertainties. Only at very high redshifts (z >~5) are there appreciable differences between models with different arα_0_ and observationally relevant values of q_0_. These tests can therefore not be used at present to determine aii and as a result the allowed range in the density parameter {OMEGA}_0_ is q_0_ <= {OMEGA}_0_ <= 2q_0_ for a given value of q_0_ (and a cosmological constant equal to zero)i The fourth classical test, the so called 'age of the universe test', is potentially much more powerful than the other three for determining the cosmological parameters, aα and {OMEGA}_0_. At present, however, age estimates are so uncertain that no definite conclusion can be drawn.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 October 1990
 Bibcode:
 1990MNRAS.246..463G