Connecting Quarks to the Cosmos Institute for Nuclear Theory 29 June to 10 July 2009 Inflationary Cosmology II Michael S. Turner Kavli Institute for Cosmological Physics The University of Chicago Michael S Turner
Successes of Standard Hot Big Bang Cosmology Big-bang nucleosynthesis Expansion of the Universe CMB Structure formation Tested account from 10-5 sec on Consistent age for the Universe (expansion, stars, radioactive elements)
Big Unanswered Questions Just like the questions raised by the SM, not a logical inconsistency but clues about Origin of baryons/large entropy per baryon Dark Matter the grander theory Dark Energy, Cosmic Acceleration, Λ Dynamite behind the big bang Heat of the big bang Isotropy, homogeneity and flatness (not generic initial conditions) Origin of seed inhomogeneity Before the big bang Addressed by Inflation
Two Horizon Problems
Two Horizon Problems Said Another Way Said 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 Inflation Addresses isotropy, homogeneity & inhomogeneity, flatness, dynamite, and before the BB Paradigm, not a model Most important idea since big bang Strong evidence supporting inflation (CMB, large-scale structure)
Key Elements of Inflation Period of exponential expansion (constant Hubble Constant and horizon size) Tremendous entropy production (called reheating)
SOLVING SOLVING
Inflation Implemented as Scalar-field Dynamics Theorists: When in doubt, just add a scalar field
Homogeneous Scalar-field is Just Like a Fluid -1 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
Entropy Production/Reheating Adiabatic: Constant Number of Photons per co-moving Volume, i.e., RT = const
Solving the Flatness, Horizon Problems
Quantum Fluctuations Seed Density Perturbations
Given scalar potential V(φ), can compute all observables in terms of V, V and V
Q: Where did the almost perfectly smooth quark soup come from? A: Decay of False Vacuum Energy!
Q: Where did the small lumps in the quark soup come from? A: Quantum Fluctuations!
Important Facts About Inflation 1. Paradigm, no standard model, many viable models (new, chaotic, ) 2. Key predictions Flat Universe: Ω 0 = 1.000 Almost scale-invariant adiabatic, almost power-law, Gaussian adiabatic fluctuations n-1 ~ 0.1, dn/dlnk ~ 10-3 Almost scale-invariant spectrum of gravitational waves n T ~ 0 to -0.1 (i.e., negative) 3. Consistency relation: T/S = -5n T Unfortunately, T/S not related to n
Important Facts About Inflation, cont d 4. Measuring GWs immediately gives scale of inflation! 5. But, no robust prediction for T/S (=r) 6. 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)
Comments about models 1. Many viable models, non-compelling 2. All based upon a weakly, coupled scalar field with small parameter (e.g., m ~ 10-6 m Pl or λ ~ 10-14 ) 3. Weakly coupled re-heating is a challenge, perturbations almost Gaussian 4. Very flat potentials 5. No hint about cosmological constant
Serious Testing of Inflation Began with WMAP and SDSS
CMB anisotropy is a non-trivial map of density inhomogeneity to temperature fluctuations: Mapping depends upon cosmological parameters (good news!) Ω M h 2 Michael S Turner
Serious testing of Inflation has begun Key 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 Results Ω 0 = 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
CDM explains all the structure that exists in the Universe today and all measurements of it only theory that does (circumstantial proof)
The Largest Things in the Universe Began from Subatomic Quantum Fluctuations! WOW!
Quantum World Projected Across the Sky by the Expansion of the Universe < one billionth the size of a proton
GWs: : The Smokin Gun Test of Inflation Directly reveals epoch of inflation Spectrum provides consistency check: T/S=-5n T Reconstruction of scalar potential NB: n T = -(T/S)/5 Direct detection: LIGO & LISA unlikely Big Bang Observer (NASA Beyond Einstein concept) B mode of CMB polarization
Reconstruction small T/S large T/S small n-1 large n-1
CMB Anisotropy from Gravity Waves ΘΘ = GW temp EE = E mode (scalar) g lensing: grav lensing of EE BB/g waves = GW B-mode
Inflation: The Challenges Precision testing: measure and Ω 0 & n-1 (to ±0.001), dn/dlnk (±0.001), search for nongaussianity Detection of GW: T/S (B modes or directly) Measure n T (need direct direction) Fundamental theory of inflation: Who is φ? Successor to inflation ( it seems like duct tape) Laboratory test of inflation (e.g., produce a φ)
Summary Inflation is a central part of the consensus cosmology ( most important idea since the big bang itself ) Strong, but not compelling evidence for inflation Important tests and challenges remain
Inflation might be the dynamite of the Big Bang, But what happened before the Big Bang?
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 MULTIVERSE
IS IT SCIENCE IF IT IS NOT TESTABLE?
We Can Test Whether or Not Our Piece of the Multiverse Originated From Inflation well on our way to doing so