Bases: astropy.cosmology.FLRW
FLRW cosmology with a CPL dark energy equation of state 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): w(z) = w_0 + w_a (1-a) = w_0 + w_a z / (1+z).
Parameters: | H0 : float or Quantity
Om0 : float
Ode0 : float
w0 : float
wa : float
Tcmb0 : float or Quantity
Neff : float
m_nu : Quantity
name : str
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Examples
>>> from astropy.cosmology import w0waCDM
>>> cosmo = w0waCDM(H0=70, Om0=0.3, Ode0=0.7, w0=-0.9, wa=0.2)
The comoving distance in Mpc at redshift z:
>>> z = 0.5
>>> dc = cosmo.comoving_distance(z)
Attributes Summary
w0 | Dark energy equation of state at z=0 |
wa | Negative derivative of dark energy equation of state w.r.t. |
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
Dark energy equation of state at z=0
Negative derivative of dark energy equation of state w.r.t. a
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
I = \left(1 + z\right)^{3 \left(1 + w_0 + 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_0 + w_a (1 - a) = w_0 + w_a \frac{z}{1+z}.