Inflation

Marc Kamionkowski
Johns Hopkins University
Cosmic Controviersies 2019???

Power at(and` . 100

C`=0 & 10 C` 2 )5

CMB is consistent with GAUSSIANITY andSTATISTICAL ISOTROPY (SI):i.e., each alm is statistically independent,
selected from a Gaussian distribution, andthere is no m dependence⇤halm al0 m0 i = Cl ll0 mm0E.g., “local-model” non-Gaussianity:If( T /T ) = t + ✏t

then2

✏T4. 10T2

0.4

0.3

0.2

0.1-4-224

Statistical isotropy: no obviously
special place on sky

Power Spectrum
CMB consistent with primordial 3d mass
distribution with power spectrum

withandP (k) / kns

ns = 0.968 ± 0.006
ns 6= 1 at & 5

….can all be accounted for• by postulating energy density in early
Universe dominated by displacement of somescalar field from minimum of its potential• Single-field slow-roll inflation

One more prediction of SFSR scenarioB modesB modes and SFSR inflation

1

ns ' 6✏r = 16 ✏If ✏ ⇠ ⌘and1then2⌘

ns & 0.014 (at 3 )r & 0.001

With or without B modes, many
unanswered questions!!
• What set the initial conditions for SFSR?
• What is the identity of the inflaton?
• How does the flatness of the potential
required for inflation arise?
• Is there a completely different paradigm toexplain measurements?

<1925SFSR
quantum~
inflationmechanics

Pre-1925 quantum mechanics
Tons of experimental values from century ofatomic spectroscopyPre-1925 quantum mechanics
Tons of experimental values from century ofatomic spectroscopy
Patterns first recognized by Balmer (1885)
Then “explained” by Bohr (1913)

Pre-1925 quantum mechanics
Tons of experimental values from ~100 years ofatomic spectroscopy, explained by…
• Simple hypothesis (Bohr quantization), pulled outof nowhere• plus kludges– Sommerfeld generalization– Pauli exclusion principle– Goudsmit-Uhlenbeck spin hypothesis– Einstein A coefficient– de Broglie wave hypothesis

1925-1930s QM/QFT

Cosmology now• Millions!! of numbers (from CMB/LSS)• Successful but simple hypotheses, but pulledfrom nowhere• lots of kludges

Places to look• Non-Gaussianity• departures from statistical isotropy• Fossils from other fields• Small-scale power• Parity breaking• Bumps and wiggles• Trans-Planckian effects

Isotropic power

A power dipole

Wired.com, 25 June 2013

Requires long-wavelength modulationof powerH-10

cannot be accounted for in SFSR!!!!

Galaxy-clustering signatures ofcoupling of inflaton to new fields

ξ(r) with single scalar mode

zyyxxh0scalar mode propagation(p=0,z)zyyxxhzξ(r) with single vector modezyyxxhx

vector mode propagation(p=x,y)zyyyxhyξ(r) with single tensor modezyyxx

h+tensor mode propagation(p=+,x)zyyxhxWork with Donghui Jeong (PSU)xSmall-scale power?

Small-scale power
21-cm fluctuations
Spectral distortions
Mini-halos
Primordial BHs
Lensing…

Parity breaking

Parity breaking• e.g., chiral GWs• Signatures in CMB E/B correlations

Bumps and wiggles• E,g., axion monodromy

V(ϕ)

ϕ

Local feature in inflaton potential?

Mendel and genetics• Mendel’s work (1865) on patterns of heredity
largely ignored for decades in part because
microscopic carriers of “factors” (notdiscovered until Crick-Watson) were not
identified• Will a “microscopic” origin for inflation
ultimately be found?