
TY  - JOUR
A1  - Ubachukwu, A. A. 
T1  - Implications of a Nonzero Cosmological Constant and Luminosity Selection Effects on Cosmological Tests
JF  - Australian Journal of Physics
JO  - Aust. J.  Phys.
Y1  - 1998
VL  - 51
IS  - 3
SP  - 585
EP  - 589
KW  - 
UR  - https://doi.org/10.1071/P97097 
N2  - This paper examines the implications of a nonzero cosmological constant &#923; 0 on the amount of linear size evolution and the luminosity selection effects usually required in the interpretation of the angular diameter&#8211;redshift (&#952;&#8211;z) test. This is based on three typical cases chosen on various plausible assumptions which can be made concerning the contribution of &#923; 0 to the density of the universe (parametrised by &OHgr;0). The results show that a fairly strong linear size evolution will be required to interpret the &#952;&#8211;z data of extended steep spectrum quasars for all three cases, if luminosity effects are neglected. However, this evolution is significantly steeper in a matter-dominated universe with &OHgr;M = &OHgr;0 = 1 than in both the flat universe with &OHgr;&#923;  = 0&#183;8, &OHgr;M = 0&#183;2 and an open universe with &OHgr;M = 0&#183;2, &#923;  = 0. Furthermore, when the luminosity selection effects present in the sample are considered, a milder size evolution is obtained for the &OHgr;M = 1, &OHgr;&#923;  = 0 model while little or no size evolution is found for the other two cases. There is therefore no significant difference in our results for an open low density universe with &OHgr;&#923;  = 0 and a flat universe dominated by &OHgr;&#923;  predicted by inflation. The present results therefore imply that an open low density universe with &OHgr;M = 0&#183;2 and &OHgr;&#923;  = 0 is compatible with an inflationary model of the universe with &OHgr;M = 0&#183;2 and &OHgr;&#923;  = 0 &#183; 8. This leads to a contradiction since the universe cannot be open and spatially closed at the same time (the existence of one should preclude the other). 
ER  -

