Horizons and Growth of Fluctuations

Question 1

Which era do we assume recombination is in?

Answer 1

matter-dominated era so ignore K and Λ

Question 2

What do we need to consider to find the comoving (photon) horizon size of at present time?

Answer 2

need to consider Λ and K

Question 3

What do we assume Ω_o to be if Λ = 0?

Answer 3

Ω_o ≡ Ωmatter,o

Question 4

What is negligible at present day?

Answer 4

Ω_radiation

Question 5

What is Ω_total?

Answer 5

Ω_total = Ω_Λ + Ω_matter + Ω_radiation

Question 6

What does the growth of structure leave?

Answer 6

A signature on the CMB

Question 7

What can Λ be assumed to be in the early universe before the end of recombination but after inflation?

Answer 7

Λ = K = 0

Question 8

What does inflation cause?

Answer 8

Density fluctuations

Question 9

What is 𝛿(𝑘)?

Answer 9

The fourier transform of the real space fluctuations 𝛿(x)

Question 10

What is the advantage of using fourier transforms?

Answer 10

The fourier modes, k, decouple from each other and evolve independently

Question 11

Are k values comoving?

Answer 11

yes