Inflation

Question 1

What is | Ωtotal – 1| for matter dominated universe?

Answer 1

∝ t^2/3 ∝ a

Question 2

What is | Ωtotal – 1| for radiation dominated universe?

Answer 2

∝ t ∝ a^2

Question 3

What happens to | Ωtotal – 1| for both radiation and matter dominated universe?

Answer 3

It grows with time

Question 4

What is | Ωtotal – 1| for recombination era?

Answer 4

0.001

Question 5

What is | Ωtotal – 1| for matter-radiation equality?

Answer 5

0.000004

Question 6

What is | Ωtotal – 1| for nucleosynthesis?

Answer 6

10^-14

Question 7

As | Ωtotal – 1| ~ 0.1 now, what must it have been in the very early universe?

Answer 7

<10^-60

Question 8

When is the CMB formed and what does this value signify?

Answer 8

At decoupling/recombination when horizon is 1-2 degrees now on sky (~150Mpc)

This is the upper limit of the size at which thermal equilibrium can happen

Question 9

What is used to explain why the CMB temperature is the same all over the sky?

Answer 9

funny particles: all unification models for particle physics predict the presence of heavy particles that should be present in early universe

they haven’t been seen yet

Question 10

What would happen to the early universe if there were too many funny particles?

Answer 10

The very early universe would be matter dominated

Question 11

What do funny particles have?

Answer 11

Magnetic monopoles
supersymmetric heavy particles (e.g. photons counterpart is photino which is heavy)

Question 11

What is inflation?

Answer 11

Any point when universe is accelerating

Question 12

What gives acceleration?

Answer 12

cosmological constant (so it satisfies inflation condition)

Question 13

What is the condition for inflation?

Answer 13

ä > 0 => p < –ρc^2 /3

Question 14

What behaviour does p = –ρc^2 /3 show?

Answer 14

free expansion

Question 15

If ä > 0 what is w?

Answer 15

w < -1/3

Question 16

What is the believed cause of inflation?

Answer 16

Symmetry breaking in particle physics which happens at “grand unification” energy ~ 10^15GeV (type I phase transition)

Question 17

What is the grand unification energy?

Answer 17

It is the combination of the strong, weak and electromagnetic forces which merge at high energies

Question 18

What does particle physics predict?

Answer 18

As temp drops equilibrium stops

A unified force that behaves like cosmological constant as symmetry breaks down which ends when fully broken

Question 19

What is a false vacuum and what is the true vaccum?

Answer 19

false vacuum: high energy symmetric state

true vacuum: lower potential energy

(original inflation views the unified force as a transition from false to true vacuum)

Question 20

Where does the energy difference between the true and the false vacuum go?

Answer 20

It is injected into the universe to cause the expansion and create all the particles we see

Question 21

What does inflation cause?

Answer 21

Density to drop to zero

Question 22

What restart particle production?

Answer 22

The energy deposited into universe at end of inflation (“reheating”)
This process gives the stuff we see around us

Question 23

What is reheating?

Answer 23

Universe goes back to temperature it would have had if inflation hadn’t happened

Question 24

When does baryon asymmetry happen?

Answer 24

after inflation

Question 25

What is a_final for inflation?

Answer 25

10^43 a_GUT which solves flatness problem as |Ω–1|∝ a^-2 ~10^-86 ~ 0 (ie Ω=1very very nearly)

Question 26

What solves the horizon problem?

Answer 26

The fact that regions that used to be in causal contact (i.e. the same temperature) become disconnected as universe expands

Question 27

What does the Grand Unified Theory (GUT) model not explain?

Answer 27

Where matter excess comes from (it must come after and perhaps due to electroweak force symmetry breaking causing type 2 phase)

Question 28

What is type 2 phase?

Answer 28

A phase change but no further inflation

Question 29

What explains the early universe well?

Answer 29

GUTs which shows inflation (E ~ 10^16GeV)

Question 30

What explains the late universe?

Answer 30

No know cause but dark energy is considered (would require an unsuspected low energy field breaking symmetry)

Question 31

When does classical physics breakdown?

Answer 31

before Planck time

Question 32

What is planck time and plancj length?

Answer 32

planck time ~ 10^ -44 s (earlier than inflation) planck length ~ 10^ -35 m

Question 33

Up to what point does the big bang model work?

Answer 33

As far as nucleosynthesis (everything beyond is speculative and requires better physical models for high energies)

Question 34

What cannot be explained without inflation in the standard model?

Answer 34

flatness of universe isotropy on super horizon scales at recombination lack of relic particles (not inflation does introduce unproven physics, questioning whether dark energy and inflation have common cause)