genFLRW.py

# -*- coding: utf-8 -*-
"""
Created on Thu Aug 21 09:40:27 2014

@author: landman

Class to create FLRW universe object

"""
from numpy import linspace, sqrt, sin, sinh, pi, ones, zeros
from scipy.interpolate import UnivariateSpline as uvs
import matplotlib.pyplot as plt

class FLRW(object):
    def __init__(self,Om0,OL0,H0,zmax,NJ):
        self.Om0 = Om0
        self.Ok0 = 1- Om0 - OL0
        self.OL0 = OL0
        self.Lambda = 3*OL0*H0**2
        self.H0 = H0
        self.NJ = NJ
        self.z = linspace(0,zmax,self.NJ)
        self.delz = self.z[1]-self.z[0]
        self.Hz = self.getHz(self.z)
        self.Om = self.getOmz()
        self.OL = self.Lambda/(3*self.Hz**2)
        self.Ok = 1 - self.Om - self.OL        
        self.getDz(self.z)
        self.nuz = self.getnuz()
        self.nu = linspace(self.nuz[0],self.nuz[-1],self.NJ)
        self.rhoz = self.getrho()
        

    def getHz(self,z):
        return self.H0*sqrt(self.Om0*(1+z)**3 + self.Ok0*(1+z)**2 + self.OL0)
            
    def getHo(self):
        Ho = uvs(self.z,self.Hz,k=5,s=0.0)
        return Ho
        
    def getDz(self,z):
        K = -self.Ok0*self.Hz[0]**2
        dDc = uvs(self.z,1/((1+self.z)**2*self.Hz),k=3,s=0.0)
        Dc = dDc.antiderivative()(z) #comoving distance
        if (K>0.0):
            self.Dz = sin(sqrt(K)*Dc)/sqrt(K)/(1+z)
        elif (K<0.0):
            self.Dz = sinh(sqrt(-K)*Dc)/sqrt(-K)/(1+z)
        else:
            self.Dz = Dc/(1+self.z)
        return
        
    def getDo(self):
        Do = uvs(self.z,self.Dz,k=5,s=0.0)
        return Do
    
    def getOmz(self):
        return self.Om0*(1+self.z)**3*(self.H0/self.Hz)**2
        
    def getrho(self):
        return 3.0*self.Om*self.Hz**2.0/(8.0*pi)
        
    def getrhoo(self):
        rho = 3.0*self.Om*self.Hz**2.0/(8.0*pi)
        rhoo = uvs(self.z,rho,k=5,s=0.0)
        return rhoo
        
    def getnuz(self):
        dvdzo = uvs(self.z,1/((1+self.z)**2*self.Hz),k=3,s=0.0)
        v = dvdzo.antiderivative()(self.z)
        return v


if __name__=="__main__":
    OL = 0.7
    Om = 0.3
    H0 = 70 / 299.8 #The 299.8 is a conversion factor to keep units consistent
    zmax = 2.0
    NJ = 500
    
    LCDM = FLRW(Om,OL,H0,zmax,NJ)
    
    #Units of rho are in Gpc^{-2} 
    plt.plot(LCDM.z,LCDM.rhoz)