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Homework 1: Integration/interpolation

Due Jan. 18.

General guidelines:

  1. Write a program to perform Romberg extrapolation of Simpson's rule for an arbitrary function.

  2. Apply the program to calculate the cosmological lookback time as a function of redshift for a cosmological model with arbitrary regular matter ($\Omega_m$) and cosmological constant ( $\Omega_\Lambda$):

    \begin{displaymath}
H_0 t(z) = \int_1^{1+z} dy\ y^{-1} \left[ \Omega_m y^3 + (1 - \Omega_m
- \Omega_\Lambda) y^2 + \Omega_\Lambda \right]^{-1/2}
\end{displaymath}

    for the models $(\Omega_m, \Omega_\Lambda) = (0.3, 0.0), (0.3, 0.3),
(0.3, 0.7)$.

    Hint: Test your program against the analytic result for the (1,0) model.

  3. Use the results to make tables of the values of redshift vs. time over the range $z = 0 - 5$. Write a program to linearly interpolate on these tables to return the lookback time given the redshift. Plot the table values as points for each of the models, and the linear interpolations as curves.

  4. Integrate to infinity to get the age of the Universe (in units of $1/H_0$) for each of the models. Be careful in considering how to properly treat the upper limit at infinity.

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The translation was initiated by Tom Quinn on 2001-02-07


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Tom Quinn 2001-02-07