How does Inflation solve the 4 puzzles?
• Puzzle #1: Flatness problem. Any slight deviation from perfectly flat is
quickly amplified with time
How does Inflation solve the 4 puzzles?
• Puzzle #1: Flatness problem. Any slight deviation from perfectly flat is
quickly amplified with time. With inflation, this is reversed!
frigg.physastro.mnsu.edu
Inflation drives the Universe toward a flat
geometry! Explains why we see Ω=1 today.
How does Inflation solve the 4 puzzles?
• Puzzle #1: Horizon problem. The CMB is the same temperature
everywhere on the sky, even though only small patches of the sky
could have been in causal contact at early times
www.astro.uva.edu
How does Inflation solve the 4 puzzles?
• Puzzle #2: Horizon problem. The CMB is the same temperature
everywhere on the sky, even though only small patches of the sky
could have been in causal contact at early times. With inflation, these
small patches were in causal contact earlier!
t~380,000 years
t~10-35 seconds
without inflation
with inflation
Idea behind inflation: exponential growth
Idea behind inflation: exponential growth
380,000 yr
Notice that objects that were once causally connected (within the horizon)
get stretched apart to outside of the horizon / become causally disconnected
Idea behind inflation: exponential growth
Objects that were once causally connected (within the horizon) get
stretched apart to outside of the horizon / become causally disconnected
… but after inflation ends, these objects can (eventually) become causally
connected again!
How does Inflation solve the 4 puzzles?
• Puzzle #3: Structure Formation problem. Why are fluctuations in
the CMB — the seeds of structure formation — the same
everywhere, and where do they come from?
How does Inflation solve the 4 puzzles?
• Puzzle #3: Structure Formation problem. Why are fluctuations in
the CMB — the seeds of structure formation — the same
everywhere, and where do they come from? Inflation explains these
seeds as quantum fluctuations in the early Universe!
time 1
time 2
time 3
How does Inflation solve the 4 puzzles?
• Puzzle #3: Structure Formation problem. Why are fluctuations in
the CMB — the seeds of structure formation — the same
everywhere, and where do they come from? Inflation explains these
seeds as quantum fluctuations in the early Universe!
• Levels of fluctuations are the same at all times; these fluctuations are
stretched with the expansion of the Universe and become the seeds
for structure formation
• These seeds can only start growing once they come back within the
horizon — so, seeds on smaller scales start to grow first. This is why
we get hierarchical growth (small objects form first, merge together
to form bigger objects)
How does Inflation solve the 4 puzzles?
• Puzzle #4: Relic problem. Why don’t we see different causal domains
— and corresponding “defects” — in our Universe?
http://wolfweb.unr.edu/homepage/yjiang/jixi_zhang.html
source: reddit
How does Inflation solve the 4 puzzles?
• Puzzle #4: Relic problem. Why don’t we see different causal domains
— and corresponding “defects” — in our Universe? With inflation, the
size of these regions gets pushed to very large scales, much bigger than
our horizon today. The density of relic defects becomes extremely
small, making it very unlikely to see them.
• Basic point: inflation spreads everything out tremendously, making the
Universe very uniform and very flat.
• Worry: does this spread out normal matter too much, too? Answer: no!
At end of inflation, energy that was driving inflation is turned into the
matter we see today, so it is not diluted.
www.chronozoom.com