Quasar populations in a cosmological constant-dominated flat universe

1995 ◽  
Vol 445 ◽  
pp. 553 ◽  
Author(s):  
Sangeeta Malhotra ◽  
Edwin L. Turner
Keyword(s):  
Cosmological Constant ◽  
Flat Universe

scholarly journals SNe Ia Redshift in a Nonadiabatic Universe

Universe ◽  
2018 ◽  
Vol 4 (10) ◽  
pp. 104 ◽  
Author(s):  
Rajendra Gupta
Keyword(s):  
Cosmological Constant ◽  
Deceleration Parameter ◽  
Hubble Constant ◽  
Cosmological Models ◽  
Single Parameter ◽  
New Approach ◽  
Cosmological Principle ◽  
Flat Universe ◽  
Λcdm Model ◽  
Two Parameters

By relaxing the constraint of adiabatic universe used in most cosmological models, we have shown that the new approach provides a better fit to the supernovae Ia redshift data with a single parameter, the Hubble constant H0, than the standard ΛCDM model with two parameters, H0 and the cosmological constant Λ related density, ΩΛ. The new approach is compliant with the cosmological principle. It yields the H0 = 68.28 (±0.53) km s−1 Mpc−1 with an analytical value of the deceleration parameter q0 = −0.4. The analysis presented is for a matter-only, flat universe. The cosmological constant Λ may thus be considered as a manifestation of a nonadiabatic universe that is treated as an adiabatic universe.

scholarly journals Global Dynamics of the Hořava–Lifshitz Cosmological Model in a Non-Flat Universe with Non-Zero Cosmological Constant

Universe ◽  
2021 ◽  
Vol 7 (11) ◽  
pp. 445
Author(s):  
Fabao Gao ◽  
Jaume Llibre
Keyword(s):  
Differential Equations ◽  
Cosmological Model ◽  
Cosmological Constant ◽  
Qualitative Theory ◽  
Global Dynamics ◽  
Model Based ◽  
Flat Universe

When the cosmological constant is non-zero, the dynamics of the cosmological model based on Hořava–Lifshitz gravity in a non-flat universe are characterized by using the qualitative theory of differential equations.

scholarly journals Nonvanishing cosmological constant of flat universe in brane-world scenario

2002 ◽  
Vol 535 (1-4) ◽  
pp. 5-10 ◽  
Author(s):  
D.K. Park ◽  
Hungsoo Kim ◽  
S. Tamaryan
Keyword(s):  
Cosmological Constant ◽  
Brane World ◽  
Flat Universe

scholarly journals Thermodynamic Prescription of Cosmological Constant in the Randall-Sundrum II Brane

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Tanwi Bandyopadhyay
Keyword(s):  
Cosmological Constant ◽  
Uncertainty Principle ◽  
Generalized Uncertainty Principle ◽  
Friedmann Equation ◽  
Entropy Function ◽  
Flat Universe ◽  
Corrected Entropy ◽  
Cosmological Scenario ◽  
Equipartition Law ◽  
The Universe

In this work, we apply the quantum corrected entropy function derived from the Generalized Uncertainty Principle (GUP) to the holographic equipartition law to study the cosmological scenario in the Randall-Sundrum (RS) II brane. An extra driving term has come up in the effective Friedmann equation for a homogeneous, isotropic, and spatially flat universe. Further, thermodynamic prescription of the universe constraints this term eventually with an order equivalent to that of the cosmological constant.

scholarly journals Implications of a Nonzero Cosmological Constant and Luminosity Selection Effects on Cosmological Tests

1998 ◽  
Vol 51 (3) ◽  
pp. 585 ◽  
Author(s):  
A. A. Ubachukwu
Keyword(s):  
Cosmological Constant ◽  
The Other ◽  
Linear Size ◽  
Low Density ◽  
Selection Effects ◽  
Flat Universe ◽  
Size Evolution ◽  
Significant Difference ◽  
Cosmological Tests ◽  
The Universe

This paper examines the implications of a nonzero cosmological constant Λ 0 on the amount of linear size evolution and the luminosity selection effects usually required in the interpretation of the angular diameter–redshift (θ–z) test. This is based on three typical cases chosen on various plausible assumptions which can be made concerning the contribution of Λ 0 to the density of the universe (parametrised by ?0). The results show that a fairly strong linear size evolution will be required to interpret the θ–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 ?M = ?0 = 1 than in both the flat universe with ?Λ = 0·8, ?M = 0·2 and an open universe with ?M = 0·2, Λ = 0. Furthermore, when the luminosity selection effects present in the sample are considered, a milder size evolution is obtained for the ?M = 1, ?Λ = 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 ?Λ = 0 and a flat universe dominated by ?Λ predicted by inflation. The present results therefore imply that an open low density universe with ?M = 0·2 and ?Λ = 0 is compatible with an inflationary model of the universe with ?M = 0·2 and ?Λ = 0 · 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).

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