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non-gaussianities
in multifield
inflation: the
approach to
adiabaticity and the
fate of fnlnavin sivanandam
[1011.4934 and 1104.5238 – joel meyers, ns]
a.i.m.s. – 21st november 2011
what is
inflation?
the universe is
the same in
every direction
but not quite
the sameexponential expansion
smooth
inhomogeneities
flatten universe
everything causally
connected
not quitequantum fluctuations
stretched and frozen
seed structure growth
negative pressure
scalar field
slow roll
flat(ish) potential
ϕ
quantum fluctuations
2 + 1 degrees of
freedom
time dependent
background
gauge invariance
scalar ζ
fluctuations
constant outside
horizon
t
comoving
wavenumber
inflation is amazing
flatness and
horizons
monopoles
gaussian and scale
invariant
inflation is
(too?)
awesome
getting beyond
“too” awesome
experiments
tensor modes
non-gaussianities
gaussian?
2pt correlation function
is the whole story
temperature Ylm
non-gaussian?
anything else
model
dependent
bispectrum
fNL
experiment
shape = physics
triangles in k-space
fNL(local) (sleight of hand
warning)
small in single field models
models
curvaton
modulated
reheating
multifield mixing
superhorizon
evolution
adiabatic?
goalcompletely
capture generating
fNL and freezing of
perturbations
outlinemodel
adiabaticity
extensions
model
2 field = isocurvature
isocurvature = trouble
multifield
models are
incomplete!
track until adiabatic
after end
thermal eq’m
1 fluid
before end
1 field phase
multifield perturb
theory hard
time-dependent
pdes
cheat – delta N
delta N switches
hard pde
problem into
easier ode one
observables
delta N
large fNLlocal, but
isocurvature
continual
superhorizon
evolution
make isocurvature
heavy
dynamic quantity
summary
next?
higher pt
more fields
potentials
adiabaticity
???
during inflation
vs
after inflation
thermal eq’m
curvaton
modulated
reheating
find toy model
that captures
distinctions in
timing of
physics
summarymaking perturbations
adiabatic kills fNLlocal
in several existing
models
how general?fNL
local is tricky
multifield models
are incomplete