Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Cosmology > Cosmo Exam Requires Writing > Flashcards

Cosmo Exam Requires Writing Flashcards

1
Q

Prove hubbles law

A

-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Show that the black body temperature is proportional to (1+z)

A

-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Find the formula for the age of the universe in terms of z

A

-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Show the expression for the angular diameter distance of an object at a certain redshift

What is interesting about this

A

-

The angular diameter distance actually turns over, objects start getting bigger as they get further away. (Due to the dimming of the surface brightness they become harder to see.)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

derive the redshift formula

A

-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Derive the Saha equation

A

-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Derive the minimum number of e foldings of inflation required to resolve the flatness problem

A

-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Derive expressions for the parameters Ω_r, Ω_m, Ω_k and Ω_Λ in terms of ρ_crit, Ho, a_o, k and Λ

A

-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Derive the dependence of the scale factor a on time r in a flat radiation dominated universe, using the fluid equation and the Friedman velocity equation

A

t^1/2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Show that including only a cosmological constant and no fluid component is equivalent to adopting a fluid with an equation of state parameter w= -1 without any cosmological constant

A

-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Sketch the comoving number density of a non-degenerate particle species in thermal equilibrium as a function of mc^2/kT. Indicate which part of the plot corresponds to a relativistic regime and which part to the non relativistic regime

A

-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Derive the acceleration equation and the Friedman equation using Newtonian dynamics. State the corollaries you use. Also derive the fluid equation.

A

The corollaries : no gravitational field inside a spherical shell of matter, can treat the gravitational attraction of a sphere as if it were concentrated at the centre.
Assume the sphere is expanding homogeneously

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Derive the time dependence of a for a flat universe for both the radiation dominated and matter dominated case

A

-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Use thermodynamics to derive the fluid equation

A

-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Derive the radiation dominated density dependence on a

A

a^-4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Derive the matter dominated density dependence on a

A

a^-3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Find the equation for critical density

A

-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Sketch the evolution of the density of RD MD CD and ΛD against log a

A

-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Derive the time dependence of a for a for a flat matter dominated universe

A

t^2/3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Derive the value of a in a closed universe such that there is no expansion

A

-

(The full solution of a(t) is symmetric around this point. It climbs from a=0 to a max and then falls back to 0 at 2tmax)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Derive the time dependence for a for a flat radiation dominated universe

A

t^1/2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Show that the universe grows exponentially at late times

A

-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Find the age of the universe for a flat, matter dominated universe

Is this consistent?

A

Hoto = 2/3

We have found objects in the universe which we believe are older than this. Hence we require the universe to be dominated by a form of matter which gives a larger value. This will have the effect of an accelerating scale factor.

24
Q

Draw a diagram of horizons in the expanding universe

A

-

25
Q

Find an expression for the proper distance to the horizon as a function of z

A

-

26
Q

Find the expression for the luminosity distance at a certain redshift

A

-

27
Q

Derive an expression for the surface brightness.

A

-

28
Q

Draw diagrams of the angular diameter distance and the luminosity distance against redshift

A

-

29
Q

Derive the dependence of density on a for an arbitrary w

A

-

30
Q

Derive the redshift of radiation matter equality

A

-

31
Q

Show that the effect of redshifting upon a black body is the black body at a new temp T = (1+z) To

A

-

32
Q

Find the ratio of baryons per photons

What relevance does this have on the matter antimatter asymmetry

A

For every billion photons there is roughly one baryon, roughly one electron. So when the universe was hot enough that electrons and positrons were considered radiation, they would have been in equilibrium with roughly equal number densities. If there is just one electron extra for every 10^9 positrons the electron would be left over when the electrons and positrons annihilated. Hence the complete present day asymmetry between matter and antimatter is due to only a one in a billion asymmetry at earlier times.

33
Q

Find the average number of interactions experienced by a particle after time t

A

-

34
Q

Find the equation which relates the density to the equilibrium density and interaction rate

A

-

35
Q

Find an expression for the neutrino density parameter and hence place a limit on the sum of the neutrino mass

A

-

36
Q

What is a wimp

A

Weakly interacting massive particle, which might be dark matter

37
Q

Write the equation for hydrogen recombination

A

-

38
Q

Write the equation for Thomson scattering

A

-

39
Q

Show that hydrogen recombination must have frozen out

A

-

40
Q

Calculate the freeze out neutron - proton ratio

A

-

41
Q

Write the crucial weak interactions

A

-

42
Q

Write the chain reactions forming deutrium and beyond

A

-

43
Q

Calculate the mass fraction of a helium nucleus

A

-

44
Q

What is the tritium path

A

-

45
Q

Show Ωk is an increasing function with z for both matter and radiation domination

A

-

46
Q

Derive the density parameter for monopoles today and show it overcloses the universe

A

-

47
Q

Draw the dependence of the scale factor and the temperature with time

A

-

48
Q

Show that inflation requires negative pressure in the early universe

A

-

49
Q

Calculate the number of N folds required to solve the horizon problem

A

-

50
Q

Calculate the number of N folds required to solve the flatness problem

A

-

51
Q

Calculate how many N folds are required to solve the monopole problem

A

-

52
Q

Derive the equation governing the scalar field

A

-

53
Q

Sketch and explain the the shape of the potential for the inflation scalar field

A

-

54
Q

Derive the expression for the particle horizon

A

-

55
Q

Calculate a numerical value for the mass fraction of helium formed by Big Bang nucelosynthesis. State any assumptions made

A

Assume all of the neutrons go into He nuclei, so the number density of helium is about half of the number density of neutrons

56
Q

Calculate the number of e foldings required for inflation to solve the monopole problem

A

-

57
Q

Draw the equilibrium ionisation fraction X as a function of redshift

A

-

Cosmology (2 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions