July 2009MPA-Garching

Michael S. TurnerKavli Institute for Cosmological Physics

The University of Chicago

2009 Biermann Lectures:“Quarks and the Cosmos”

I. Cosmic Acceleration and Dark Energy (8 July) I. Inflation and Beyond (23 July)I. Future Opportunities and Challenges (28 July)

Michael S Turner

Cosmology Cosmology is a is a

young scienceyoung science

… its story only begins 60 years after Darwin, 300 years after the

invention of the telescope

Michael S Turner

Progress driven by powerful ideas and

instruments(especially last 25 years)

Gamow’s Hot Big Bang“alpher, bethe, gamow,” 1948

Michael S Turner

Michael S Turner

Two Really Important IdeasTwo Really Important IdeasThat Changed CosmologyThat Changed Cosmology

with deep connections between quarks and the cosmos

Inflation:Inflation: brief period of rapid (accelerated) expansion accounts for smoothness, flatness; heat of the big bang; and seed inhomogeneities

Particle dark matter:Particle dark matter: bulk of the dark matter that holds the Universe together resides in a sea of elementary particles left over from the big bang

Michael S Turner

Cold Dark Matter Transformed “Astrophysical Cosmology”

… and this Institute!

Profound Connections

Between Quarks and the Cosmos

Basic Features of the Universe

tied to Fundamental

Physics

Michael S Turner

The “Consensus Cosmology”The “Consensus Cosmology”based upon precision measurements

• From quark soup to nuclei and atoms to galaxies and large-scale structure• Flat, accelerating Universe; ΛCDM structure formation• Atoms, exotic dark matter & dark energy• Consistent with inflation• Precision parameters

–Ω0 = 1.005 ± 0.006 (uncurved)–ΩM = 0.280 ± 0.013–ΩB = 0.045 ± 0.0015–ΩDE = 0.72 ± 0.015–H0 = 70 ± 1.3 km/s/Mpc–t0 = 13.73 ± 0.12 Gyr–Nν = 4.4 ± 1.5

Michael S Turner

Inflation: Inflation: Time for CelebrationTime for Celebration

or Time for a Change?or Time for a Change?

See, M.S. Turner, Nature Physics 4, 89 (2008)

Successes of Standard Hot Successes of Standard Hot Big Bang CosmologyBig Bang Cosmology

circa 1980

• Expansion of the Universe• Big-bang nucleosynthesis (BBN)• Cosmic Microwave Background (CMB)• Structure formation by gravitational

instability

“Reliable account of the Universe from 10-5 seconds until today”

Big Unanswered QuestionsBig Unanswered Questionscirca 1980

• Origin of baryons• Cosmological constant problem• Before the big bang/initial singularity• Nature of dark matter• Dynamite behind the big bang• Heat of the big bang• Isotropy, homogeneity and flatness (not generic

initial conditions)• Origin of seed inhomogeneity Addressed by Inflation

““Two Horizon Problems”Two Horizon Problems”

““Two Horizon Problems”Two Horizon Problems”

Said Another WaySaid Another Way• Horizon at last scattering subtends only 1

degree on the sky; what mechanism causes the temperature to be so uniform on scales » 1 degree?

• Galactic-sized masses entered the horizon about 1 year after the big bang; what causal physics created density perturbations that late in the history of Universe?

Cosmic InflationCosmic Inflation

• Addresses isotropy, homogeneity & inhomogeneity, flatness, dynamite, and heat of the BB

• Lessens (does not eliminate) dependence upon initial data

• Paradigm, not a model

The 2 Elements of InflationThe 2 Elements of Inflation

1. Period of exponential expansion (constant Hubble Constant and horizon size)

“superluminal expansion’

1. Tremendous entropy production (called reheating)

SOLVING

SOLVING

Inflation Implemented as Inflation Implemented as Scalar-field DynamicsScalar-field Dynamics

Theorists: When in

doubt, just add a

scalar field

Solving the Flatness, Horizon Problems

Entropy Entropy Production/ReheatingProduction/Reheating

Adiabatic: Constant Adiabatic: Constant Number of Photons per Number of Photons per co-moving Volume, i.e., co-moving Volume, i.e.,

RT = constRT = const

Quantum Fluctuations Seed Quantum Fluctuations Seed Density PerturbationsDensity Perturbations

Homogeneous Scalar-field is Homogeneous Scalar-field is Just Like a FluidJust Like a Fluid

• Slow roll (flat part of potential): w ≈ -1• Rapid oscillation: particle production and

conversion of potential energy to particles (heat) aka decay of φ particles

≈ -1

Given scalar potential V(φ), can compute

observables in terms of V, V’

and V’’

• S = square of CMB quadrupole due to density perturbations ≈ 10-10 • T = square of CMB quadrupole due to density perturbations≈ ??• r = T/S

Q:Q: Where did the Where did the almost perfectly almost perfectly

smooth hot quark smooth hot quark soup come from? soup come from?

A:A: Decay of False Decay of False Vacuum Energy!Vacuum Energy!

Q:Q: Where did the Where did the small lumps in the small lumps in the quark soup come quark soup come

from? from?

A:A: Quantum Quantum Fluctuations!Fluctuations!

The Largest Things in the Universe The Largest Things in the Universe Began from Subatomic Quantum Began from Subatomic Quantum

Fluctuations!Fluctuations!

WOW!WOW!

Quantum World Projected Across the Quantum World Projected Across the Sky by the Expansion of the UniverseSky by the Expansion of the Universe

< one billionth the size< one billionth the size of a protonof a proton

Important Facts About InflationImportant Facts About Inflation1. Paradigm, no standard model, many

viable models (new, chaotic, …)2. Key predictions

• Flat Universe: Ω0 = 1.000• Almost scale-invariant adiabatic, almost

power-law, nearly Gaussian adiabatic fluctuations

• |n-1| ~ O(0.1), |dn/dlnk| ~ O(10-3)• Almost scale-invariant spectrum of

gravitational waves• nT ~ 0 to -0.1 (i.e., negative)

3. Consistency relation: T/S = -5nT

• Unfortunately, T/S not directly related to n

Important Facts About Important Facts About Inflation, cont’dInflation, cont’d

1. Measuring GWs immediately gives scale of inflation!

1. But, no robust prediction for T/S (=r)2. Inflationary perturbations + Cold

Dark Matter + “Λ” = ΛCDM scenario for structure formation (another test)

T/S > 0.001 if n > 0.9?Hoffman/Turner, PRD 64, 02350 (2001)

Important Facts About Inflation, Important Facts About Inflation, cont’dcont’d

7. Inflaton is described by a very weakly coupled scalar field, weak coupling makes reheating inefficient

1. Conditions for successful inflation1. δρ/ρ ≈ 10-5 (hardest)2. > 60 e-folds of inflation (easy)3. Reheating to > 10 MeV (BBN), xx GeV

(baryogenesis)4. No unwanted debris (e.g., gravitinos,

moduli fields, …)

Testing Inflation!for almost 20 years an oxymoron

Michael S Turner

1992: COBE 1992: COBE Maps & Maps &

BlackBody BlackBody SpectrumSpectrum

Michael S Turner

COBE Proves Copernicus

Right!

WMAP uses this signal for calibration

Michael S Turner

TOCO

BOOMERanG

DASI

CMB ExperimentsCMB Experiments

Maxima CBI

VSA ACBARACBAR

CBI

SPT

ACT

QUAD/BICEP/KECK

PolarBearCAPMAP

CMB ExperimentsCMB Experiments

Michael S Turner

Wilkinson Microwave Anisotropy Wilkinson Microwave Anisotropy Probe (WMAP)Probe (WMAP)

±0.001% Fluctuations

Michael S Turner

Curve = concordance cosmology

Serious testing of Serious testing of Inflation has Inflation has begunbegun

Key PredictionsKey Predictions• Flat Universe• Almost scale-invariant, Gaussian perturbations: |(n-1)| ~ 0.1 and |dn/dlnk| ~ 0.001• Gravity waves: spectrum, but not amplitude • Cold Dark Matter Scenario

Key ResultsKey Results• Ω0 = 1.0 ± 0.006• (n-1) = -0.04 ± 0.014*; dn/dlnk = -0.032 ± 0.02; no

evidence for nonGaussianity• r < 0.2 (95% cl)*

*Depends significantly upon the priors assumed

Michael S Turner

Cold Dark Matter Cold Dark Matter ScenarioScenario

= Particle DM + Inflation

Structure Forms From the Bottom Up:

First Stars (z ~ 10 -20) Galaxies (z ~ 2 – 5), Clusters (z ~ 0 - 2), and Superclusters

(z ~ 0)

Michael S Turner

Tracing the history from a slightly lumpy Universe to galaxies ablaze

First significant evidence for

inflation – still a long road ahead

until it is “proven.’

Inflation: Inflation: The Challenges AheadThe Challenges Ahead

I. Observational – precision testing

II. Foundational – conceptual + laboratory evidence

Precision Testing of InflationPrecision Testing of Inflation

• Measure and Ω0 to ±0.001 = 1.000?• Measure n-1 to ±0.001 = ±O(0.1)?• Detect dn/dlnk ±O(0.001)• Gaussianity fNL ~ O(0.1)• Detection of GW: T/S = ?

– CMB B mode polarization; or direct detection

• Measure nT T/S = -5nT?– CMB B-mode or CMB + direct detection

Michael S Turner

• Successful Launch: 14 May 2009• Coolest thing in space (100 mK)• Ω0, n-1, dn/dlnk, Gaussianity, B-mode polarization?

Michael S Turner

Coming Soon: Planck Surveyor Launch 2008 Cosmic Variance Limited to l ~ 2500

(vs WMAP to l ~ 1000) + polarization

GWs: The Smokin’ GunGWs: The Smokin’ Gun• Directly reveals epoch of inflation

• Reconstruct scalar potential

• Spectrum provides consistency check: T/S=-5nT

• Direct detection: – LIGO & LISA unlikely; “Big Bang Observer” (a dream)

• B mode of CMB polarization

Reconstruction Reconstruction

smallT/S

largeT/S

small n-1 large n-1

E mode

B mode

CMB Anisotropy

from Gravity Waves

• ΘΘ = GW temp• EE = E mode

(scalar)• g lensing: grav lensing of EE• BB/g waves = GW B-mode• Detect T/S >

0.001?

Discovery of CMBpolarization:DASI, 2002

Kovac et al, Nature 420, 772 (2002)

Pola

rizat

ion:

Whe

re w

e ar

e to

day

Chi

ang

et a

l, ar

Xiv:

090

6.11

81

r = 0.1

CMBPol / Astro2010

Science Objectives for a Space Mission

CMB Community Reports Probing Inflation with CMB Polarization, Baumann et al. 2008, ArXiv 0811.3919 Gravitational Lensing, Smith et al. 2008, ArXiv 0811.3916 Reionization Science with the CMB, Zaldarriaga et al. 2008, ArXiv 0811.3918 Prospects for Polarized Foreground Removal, Dunkley et al. 2008, ArXiv 0811.3915 Foreground Science Knowledge and Prospects, Fraisse et al. 2008, ArXiv 0811.3920

8 yrs

1.2 yrs

4 yrs

CMBPol / Astro2010

How Sub-Orbital Program Benefits a Satellite Mission

Historical Interplay: Suborbital Experiments serve to

- Shape scientific objective of a space mission - Develop experimental methodologies- Train leaders of future orbital missions - Develop technologies at systems level

COBE1989

WMAP2001

Planck2009

Sensitivity

60xSensitivity

20xSensitivity

>20x

CMBPOL2022

100 nK1 µK100 µK few nK

Archeops, Boomerang, MaximaWoody-Richards

U2-DMR

QMAP, SK, TOCO

Sat

ellit

e M

issi

onS

ub-O

rbita

l Pre

curs

or

Multiple

Ground-based&

Balloon-borne

FoundationalFoundational• Fundamental theory of inflation: Who is φ?

– Many, many models, no compelling theory– “Landau-Ginzburg” theory of inflation

• Laboratory test of inflation to close the circle (e.g., produce a φ)– Recall, “believe in BBN” because of laboratory

measurements (nuclei, nuclear physics cross sections, etc)

– NB: dark matter is on the same path.

Shortcomings of InflationShortcomings of Inflation

Great theory, but …Great theory, but …• No fundamental theory (still at Landau

Ginzburg stage – is there a BCS theory?)• Does not address initial singularity

– geodesically incomplete• Like “duct tape”, very useful but …

– Only postpones appearance of inhomogeneity– not all initial conditions inflate

• Quantum unpredictability• No laboratory signature/test

Time to be bold again!Time to be bold again!some ideas

• Ekpyrotic (brane-collisions, s l o w c o l l a p s e rather than rapid expansion

NB: solve horizon problem by d2a/dt2 and da/dt having same sign, positive or negative

• Cyclic (multiple brane collisions)• Variable speed of light??• Pre big bang

No well developed competitor for inflation yetPotential signatures: nonGaussianity, detection of

gravity waves (anti-signature)

SummarySummary• Inflation addresses important shortcomings of the

standard model and has been the driving force in cosmology for 3 decades

• First significant evidence for inflation (flat Universe, nearly scale-invariant, Gaussian density perturbations)

• Precision tests of inflation coming soon!• GWs are smokin’ gun signature (but only

detectable if r > 0.001?)• Foundational challenges: compelling model &

laboratory tests• Time for a new bolder idea?

Michael S Turner

Time for Celebrationor a New Idea?

Time will tell

In any case a most exciting time,

maybe even a Golden Age

Theorists needed!

Question is now within the realm of science

Three ideas – all probably wrong!

neat & tidy!… but Einstein’s theory does not

incorporate quantum

mechanics.… and the

conditions at the beginning are precisely

where quantum effects should

be critical!

Einstein got the right

answer for the wrong

reason!

= Emergence of space and time

THE MULTIVERSETHE MULTIVERSE

IS IT SCIENCE IF IT IS NOT TESTABLE?IS IT SCIENCE IF IT IS NOT TESTABLE?

We Can Test Whether or We Can Test Whether or Not “Our Piece of the Not “Our Piece of the

Multiverse” Originated Multiverse” Originated From InflationFrom Inflation

… well on our way to doing so

BRANE WORLD OF STRING BRANE WORLD OF STRING THEORYTHEORY

WE LIVE ON A 3WE LIVE ON A 3DD BRANE IN AN 11 BRANE IN AN 11DD SPACE SPACEBRANES COLLIDE CREATING BIG BANGSBRANES COLLIDE CREATING BIG BANGS

Vacuum Energy Problem Solved Vacuum Energy Problem Solved by Supersymmetry or ?by Supersymmetry or ?

Quantum Fluctuations Seed Quantum Fluctuations Seed Galaxies and Clusters!Galaxies and Clusters!