Description Usage Arguments Details Value Author(s) References Examples
Derive full set of cosmological density parameters from a partial set
1 | cosmo_param(omega_m, omega_lambda, omega_k, q0)
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omega_m |
normalized matter energy density, non-negative scalar |
omega_lambda |
normalized cosmological constant, scalar |
omega_k |
normalized curvature parameter, scalar (= 0 for a flat universe |
q0 |
deceleration parameter, scalar (= -R*(R”)/(R')^2 = 0.5*omega_m - omega_lambda) |
This procedure is called by lumdist and galage to allow the user a choice in defining any two of four cosmological density parameters.
Given any two of the four input parameters – (1) the normalized matter density omega_m (2) the normalized cosmological constant, omega_lambda (3) the normalized curvature term, Omega_k and (4) the deceleration parameter q0 – this program will derive the remaining two. Here "normalized" means divided by the closure density so that omega_m + omega_lambda + omega_k = 1. For a more precise definition see Carroll et al (1992).
If fewer than two parameters are defined, this procedure sets default values of omega_k=0 (flat space), omega_lambda = 0.7, omega_m = 0.3 and q0 = -0.55
If more than two parameters are defined upon input (overspecification), then the first two defined parameters in the ordered list omega_m, omega_lambda, omega_k, q0 are used to define the cosmology.
omega_m |
normalized matter energy density, non-negative scalar |
omega_lambda |
normalized cosmological constant, scalar |
omega_k |
normalized curvature parameter, scalar (= 0 for a flat universe |
q0 |
deceleration parameter, scalar (= -R*(R”)/(R')^2 = 0.5*omega_m - omega_lambda) |
Written by W. Landsman Raytheon ITSS April 2000
R adaptation by Arnab Chakraborty (June 2013)
Carroll, S. M., Press, W. H. & Turner, E. L., The cosmological constant, Ann. Rev. Astro. Astrophys, 30, 499, 1992. http://www.annualreviews.org/doi/pdf/10.1146/annurev.aa.30.090192.002435
1 | cosmo_param(0.3, NULL, 1.0, NULL) # returns omega_lambda=0.7 and q0=-1.05
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