Inflation Flashcards
What is | Ωtotal – 1| for matter dominated universe?
∝ t^2/3 ∝ a
What is | Ωtotal – 1| for radiation dominated universe?
∝ t ∝ a^2
What happens to | Ωtotal – 1| for both radiation and matter dominated universe?
It grows with time
What is | Ωtotal – 1| for recombination era?
0.001
What is | Ωtotal – 1| for matter-radiation equality?
0.000004
What is | Ωtotal – 1| for nucleosynthesis?
10^-14
As | Ωtotal – 1| ~ 0.1 now, what must it have been in the very early universe?
<10^-60
When is the CMB formed and what does this value signify?
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
What is used to explain why the CMB temperature is the same all over the sky?
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
What would happen to the early universe if there were too many funny particles?
The very early universe would be matter dominated
What do funny particles have?
Magnetic monopoles
supersymmetric heavy particles (e.g. photons counterpart is photino which is heavy)
What is inflation?
Any point when universe is accelerating
What gives acceleration?
cosmological constant (so it satisfies inflation condition)
What is the condition for inflation?
ä > 0 => p < –ρc^2 /3
What behaviour does p = –ρc^2 /3 show?
free expansion
If ä > 0 what is w?
w < -1/3
What is the believed cause of inflation?
Symmetry breaking in particle physics which happens at “grand unification” energy ~ 10^15GeV (type I phase transition)
What is the grand unification energy?
It is the combination of the strong, weak and electromagnetic forces which merge at high energies
What does particle physics predict?
As temp drops equilibrium stops
A unified force that behaves like cosmological constant as symmetry breaks down which ends when fully broken
What is a false vacuum and what is the true vaccum?
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)
Where does the energy difference between the true and the false vacuum go?
It is injected into the universe to cause the expansion and create all the particles we see
What does inflation cause?
Density to drop to zero
What restart particle production?
The energy deposited into universe at end of inflation (“reheating”)
This process gives the stuff we see around us
What is reheating?
Universe goes back to temperature it would have had if inflation hadn’t happened
When does baryon asymmetry happen?
after inflation
What is a_final for inflation?
10^43 a_GUT which solves flatness problem as |Ω–1|∝ a^-2 ~10^-86 ~ 0 (ie Ω=1very very nearly)
What solves the horizon problem?
The fact that regions that used to be in causal contact (i.e. the same temperature) become disconnected as universe expands
What does the Grand Unified Theory (GUT) model not explain?
Where matter excess comes from (it must come after and perhaps due to electroweak force symmetry breaking causing type 2 phase)
What is type 2 phase?
A phase change but no further inflation
What explains the early universe well?
GUTs which shows inflation
(E ~ 10^16GeV)
What explains the late universe?
No know cause but dark energy is considered (would require an unsuspected low energy field breaking symmetry)
When does classical physics breakdown?
before Planck time
What is planck time and plancj length?
planck time ~ 10^ -44 s
(earlier than inflation)
planck length ~ 10^ -35 m
Up to what point does the big bang model work?
As far as nucleosynthesis
(everything beyond is speculative and requires better physical models for high energies)
What cannot be explained without inflation in the standard model?
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)
