Solution of Friedmann equation w/ Cosmological Constant

nicksauce
Science Advisor
Homework Helper
Messages
1,270
Reaction score
7

Homework Statement


Solve for the age of the universe as a function of scale factor in a cosmology with \Omega_{M}=0.3, \Omega_{\Lambda}=0.7.

Homework Equations


The Attempt at a Solution


(\frac{\dot{a}}{a})^2=H_0^2(0.3a^{-3}+0.7)

\frac{da}{a\sqrt{0.3a^{-3}+0.7}}=H_0dt

At this point, Maple seems unable to do this integral, and I am stuck. Any tips?Errr... Nevermind, I got it to work eventually.
 
Last edited:
Physics news on Phys.org
nicksauce said:
Errr... Nevermind, I got it to work eventually.

Would you mind sharing? Some people may find it useful!
 
Thread 'Need help understanding this figure on energy levels'
This figure is from "Introduction to Quantum Mechanics" by Griffiths (3rd edition). It is available to download. It is from page 142. I am hoping the usual people on this site will give me a hand understanding what is going on in the figure. After the equation (4.50) it says "It is customary to introduce the principal quantum number, ##n##, which simply orders the allowed energies, starting with 1 for the ground state. (see the figure)" I still don't understand the figure :( Here is...
Thread 'Understanding how to "tack on" the time wiggle factor'
The last problem I posted on QM made it into advanced homework help, that is why I am putting it here. I am sorry for any hassle imposed on the moderators by myself. Part (a) is quite easy. We get $$\sigma_1 = 2\lambda, \mathbf{v}_1 = \begin{pmatrix} 0 \\ 0 \\ 1 \end{pmatrix} \sigma_2 = \lambda, \mathbf{v}_2 = \begin{pmatrix} 1/\sqrt{2} \\ 1/\sqrt{2} \\ 0 \end{pmatrix} \sigma_3 = -\lambda, \mathbf{v}_3 = \begin{pmatrix} 1/\sqrt{2} \\ -1/\sqrt{2} \\ 0 \end{pmatrix} $$ There are two ways...
Back
Top