Bases: astropy.cosmology.FLRW
FLRW cosmology with a CPL dark energy equation of state, a pivot redshift, and curvature.
The equation for the dark energy equation of state uses the CPL form as described in Chevallier & Polarski Int. J. Mod. Phys. D10, 213 (2001) and Linder PRL 90, 91301 (2003), but modified to have a pivot redshift as in the findings of the Dark Energy Task Force (Albrecht et al. arXiv:0901.0721 (2009)): w(a) = w_p + w_a (a_p - a) = w_p + w_a( 1/(1+zp) - 1/(1+z) ).
Parameters: | H0 : float or Quantity
Om0 : float
Ode0 : float
wp : float
wa : float
zp : float
Tcmb0 : float or Quantity
Neff : float
m_nu : Quantity
name : str
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Examples
>>> from astropy.cosmology import wpwaCDM
>>> cosmo = wpwaCDM(H0=70, Om0=0.3, Ode0=0.7, wp=-0.9, wa=0.2, zp=0.4)
The comoving distance in Mpc at redshift z:
>>> z = 0.5
>>> dc = cosmo.comoving_distance(z)
Attributes Summary
wa | Negative derivative of dark energy equation of state w.r.t. |
wp | Dark energy equation of state at the pivot redshift zp |
zp | The pivot redshift, where w(z) = wp |
Methods Summary
de_density_scale(z) | Evaluates the redshift dependence of the dark energy density. |
w(z) | Returns dark energy equation of state at redshift z. |
Attributes Documentation
Negative derivative of dark energy equation of state w.r.t. a
Dark energy equation of state at the pivot redshift zp
The pivot redshift, where w(z) = wp
Methods Documentation
Evaluates the redshift dependence of the dark energy density.
Parameters: | z : array_like
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Returns: | I : ndarray, or float if input scalar
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Notes
The scaling factor, I, is defined by \rho(z) = \rho_0 I, and in this case is given by
a_p = \frac{1}{1 + z_p} I = \left(1 + z\right)^{3 \left(1 + w_p + a_p w_a\right)} \exp \left(-3 w_a \frac{z}{1+z}\right)
Returns dark energy equation of state at redshift z.
Parameters: | z : array_like
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Returns: | w : ndarray, or float if input scalar
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Notes
The dark energy equation of state is defined as w(z) = P(z)/\rho(z), where P(z) is the pressure at redshift z and \rho(z) is the density at redshift z, both in units where c=1. Here this is w(z) = w_p + w_a (a_p - a) where a = 1/1+z and a_p = 1 / 1 + z_p.