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