Basic Idea: When there is a cosmological constant
the expansion of the universe accelerates, and inflation (an
accelerated expansion) is desirable at least in early stages of
the history of the universe. That is, it happened
before, so maybe it could happen again.
Effects of dominance by lambda: Flatness, emptiness, horizons.
More generally result of inflation or accelerated expansion.
Motivation for inflation
- observed homogeneity and isotropy
including no weird heavy particles from high energy physics
- combined with horizons and finite age--
need acausal behavior
Mathematically- acceleration depends on energy and pressure.
Positive vacuum energy pushes out rather than attracting.
Particle physics and inflation
- usual method to get inflation: some field gets stuck and gives approx constant
- inflation starts
- inflation ends
- timing :any time before bbn
- extra bonus: generate initial conditions (particle creation)
"Who is the inflaton?"
generic results both a strength and a weakness
Current questions in the field today: quantum cosmology,
reheating, theories which give inflation, reconstruction
Things of note:
- Inflation may have happened via lambda--and if then
why not now too?
- Maybe all the potential energy didn't go into particles
and so our current lambda is related to the earlier one
- If lambda then was via a field maybe something that looks like
lambda now is also via a field, and transient.
that isn't quite acting like lambda but almost (loses energy with
expansion but not as fast as e.g. matter).