File:Mplwp universe scale evolution.svg
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Summary
| Description |
English: Plot of the evolution of the size of the universe (scale parameter a) over time (in billion years, Gyr). Different models are shown, which are all solutions to the Friedmann equations with different parameters. The evolution is governed by the equation
Here is the radiation density, the matter density, the curvature parameter and the dark energy, all normalized such that represents the fact that today's expansion rate is .
|
| Date | |
| Source | Own work |
| Author | Geek3 |
| SVG development |  This plot was created with mplwp, the Matplotlib extension for Wikipedia plots. |
| Source code | Python code#!/usr/bin/python
# -*- coding: utf8 -*-
import matplotlib.pyplot as plt
import matplotlib as mpl
import numpy as np
from math import *
code_website = 'http://commons.wikimedia.org/wiki/User:Geek3/mplwp'
try:
import mplwp
except ImportError, er:
print 'ImportError:', er
print 'You need to download mplwp.py from', code_website
exit(1)
name = 'mplwp_universe_scale_evolution.svg'
fig = mplwp.fig_standard(mpl)
fig.set_size_inches(600 / 72.0, 450 / 72.0)
mplwp.set_bordersize(fig, 58.5, 16.5, 16.5, 44.5)
xlim = -17, 22; fig.gca().set_xlim(xlim)
ylim = 0, 3; fig.gca().set_ylim(ylim)
mplwp.mark_axeszero(fig.gca(), y0=1)
import scipy.optimize as op
from scipy.integrate import odeint
tH = 978. / 68. # Hubble time in Gyr
def Hubble(a, matter, rad, k, darkE):
# the Friedman equation gives the relative expansion rate
a = a[0]
if a <= 0: return 0.
r = rad / a**4 + matter / a**3 + k / a**2 + darkE
if r < 0: return 0.
return sqrt(r) / tH
def scale(t, matter, rad, k, darkE):
return odeint(lambda a, t: a*Hubble(a, matter, rad, k, darkE), 1., [0, t])
def scaled_closed_matteronly(t, m):
# analytic solution for matter m > 1, rad=0, darkE=0
t0 = acos(2./m-1) * 0.5 * m / (m-1)**1.5 - 1. / (m-1)
try: psi = op.brentq(lambda p: (p - sin(p))*m/2./(m-1)**1.5
- t/tH - t0, 0, 2 * pi)
except Exception: psi=0
a = (1.0 - cos(psi)) * m * 0.5 / (m-1.)
return a
# De Sitter http://en.wikipedia.org/wiki/De_Sitter_universe
matter=0; rad=0; k=0; darkE=1
t = np.linspace(xlim[0], xlim[-1], 5001)
a = [scale(tt, matter, rad, k, darkE)[1,0] for tt in t]
plt.plot(t, a, zorder=-2,
label=ur'$\Omega_\Lambda=1$, de Sitter')
# Standard Lambda-CDM https://en.wikipedia.org/wiki/Lambda-CDM_model
matter=0.3; rad=0.; k=0; darkE=0.7
t0 = op.brentq(lambda t: scale(t, matter, rad, k, darkE)[1,0], -20, 0)
t = np.linspace(t0, xlim[-1], 5001)
a = [scale(tt, matter, rad, k, darkE)[1,0] for tt in t]
plt.plot(t, a, zorder=-1,
label=ur'$\Omega_m=0.\!3,\Omega_\Lambda=0.\!7$, $\Lambda$CDM')
# Empty universe
matter=0; rad=0; k=1; darkE=0
t0 = op.brentq(lambda t: scale(t, matter, rad, k, darkE)[1,0], -20, 0)
t = np.linspace(t0, xlim[-1], 5001)
a = [scale(tt, matter, rad, k, darkE)[1,0] for tt in t]
plt.plot(t, a, label=ur'$\Omega_k=1$, empty universe', zorder=-3)
'''
# Open Friedmann
matter=0.5; rad=0.; k=0.5; darkE=0
t0 = op.brentq(lambda t: scale(t, matter, rad, k, darkE)[1,0], -20, 0)
t = np.linspace(t0, xlim[-1], 5001)
a = [scale(tt, matter, rad, k, darkE)[1,0] for tt in t]
plt.plot(t, a, label=ur'$\Omega_m=0.\!5, \Omega_k=0.5$')
'''
# Einstein de Sitter http://en.wikipedia.org/wiki/Einstein–de_Sitter_universe
matter=1.; rad=0.; k=0; darkE=0
t0 = op.brentq(lambda t: scale(t, matter, rad, k, darkE)[1,0], -20, 0)
t = np.linspace(t0, xlim[-1], 5001)
a = [scale(tt, matter, rad, k, darkE)[1,0] for tt in t]
plt.plot(t, a, label=ur'$\Omega_m=1$, Einstein de Sitter', zorder=-4)
'''
# Radiation dominated
matter=0; rad=1.; k=0; darkE=0
t0 = op.brentq(lambda t: scale(t, matter, rad, k, darkE)[1,0], -20, 0)
t = np.linspace(t0, xlim[-1], 5001)
a = [scale(tt, matter, rad, k, darkE)[1,0] for tt in t]
plt.plot(t, a, label=ur'$\Omega_r=1$')
'''
# Closed Friedmann
matter=6; rad=0.; k=-5; darkE=0
t0 = op.brentq(lambda t: scaled_closed_matteronly(t, matter)-1e-9, -20, 0)
t1 = op.brentq(lambda t: scaled_closed_matteronly(t, matter)-1e-9, 0, 20)
t = np.linspace(t0, t1, 5001)
a = [scaled_closed_matteronly(tt, matter) for tt in t]
plt.plot(t, a, label=ur'$\Omega_m=6, \Omega_k=\u22125$, closed', zorder=-5)
plt.xlabel('t [Gyr]')
plt.ylabel(ur'$a/a_0$')
plt.legend(loc='upper left', borderaxespad=0.6, handletextpad=0.5)
plt.savefig(name)
mplwp.postprocess(name)
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Licensing
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File history
Click on a date/time to view the file as it appeared at that time.
| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 00:12, 17 April 2017 | | 600 × 450 (57 KB) | Geek3 | validator fix |
| 22:33, 16 April 2017 |  | 600 × 450 (57 KB) | Geek3 | {{Information |Description ={{en|1=Plot of the evolution of the size of the universe (scale parameter ''a'') over time (in billion years, Gyr). Different models are shown, which are all solutions to the {{W|Friedmann equations|Friedmann equations}}... |
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