Cosmo Study Thing

Superfun study time

16. What are the Friedman equations? Under what circumstances do the Friedman equations describe the dynamics of the Universe? How does one test these assumptions?

Friedmann equations are a set of equations that govern the expansion of space. They require a homogeneous and isotropic universe. These assumptions can be tested from the uniformity of the CMB and the power sepectrum at distances larger than about 100 Mpc.

17. What physics determines the location of the peak in this plot? Be able to explain why this plot is expected in a Lambda-Cold Dark Matter universe and how an alternative dark matter candidate (e.g. Hot Dark Matter) is ruled out by measurements like these. Be able to explain what measurements are made to create a plot like this.

Size of particle horizon at epoch of matter-radiation equality determines the location of the peak.
Radiation opposes gravity during radiation dominated era - free steaming stops small scale growth. Large wavenumber stuff wouldn’t be there if there was HDM. I can’t really explain these measurements....

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