By Michał Heller, Zbigniew Klimek, Konrad Rudnicki (auth.), M. S. Longair (eds.)
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Extra resources for Confrontation of Cosmological Theories with Observational Data
The limIts that can be set on the value of the cosmologIcal constant wIll be dIscussed m SectIon 3. In section 4 I shall reVIew the properties of the Lemaitre models. These models, because of theIr quaSI-statIc period, are the only models whose observatIOnal characterIstics are drastIcally dIfferent from the rest of the general relatIVIstic models. Therefore they prOVIde the strongest motIvation for retammg the cosmologIcal constant m the Emstem field equatIons. In SectIon 4 I shall first re-examme the motIvatIOn for the mtroductIon of these models by Lemaitre m the 1930's, then the reason for ItS re-mtroductlOn by Salpeter, Szekeres and myself in 1967 and discuss them m the lIght of present day observatIOns.
3", we obtain the lImIt IAI< 10- 42 cm- 2 . This, however, IS not a useful hmIt. If A were as large as this, the Newtonian equations would break down at dIstances of about one kpc from any body. This IS contrary to observatIOn of the dynamics of our Galaxy. v/c 2 must be less than the matter denSIty m clusters; Qv;:51O- 2B g cm- 3 or IAI< 6 x 10- 55 cm- 2 . ThIS hmIt also IS larger than the values allowed from cosmolOgIcal considerations, whIch are dIscussed in the next section. 3. Limits on A from Cosmological Observations WIth the cosmologIcal constant one obtains numerous isotropIc and homogeneous cosmologIcal models whIch are known as the Friedmann-Lemaitre models.
The stability of the static models was examined by various authors dunng the period 1930 to 1950 whIch IS revIewed by North (1965). Most of the mvestigatIOns during this period were concerned with stablhty against the formatIOn of condensatIOns without consIdering the most Important effect, namely the changes III the equatIOn of state dunng the formatIOn of these condensations Lemaitre (1931), however, did consIder this effect He argued that dunng the formation of condensatIOns from a gas with temperature T, the pressure IS reduced from nkT to zero if all matter IS locked m the condensatIOns.