COMING HOMECOMING HOME

Michael S. Turner

Kavli Institute for Cosmological Physics

The University of Chicago

Some Cosmological Some Cosmological Observations from AfarObservations from Afar

No Chinks in “The No Chinks in “The New Cosmology”New Cosmology”

• WMAP + SDSS + 2dF + HST Key Project + DASI + ACBAR + CBI + t0 + SNe …

• Smaller error bars, consistency remains– σ(n): 0.1 to 0.02; σ(Ω0): 0.03 to 0.01; σ(w): 0.2 to

0.1

• Hubble constant has been constant for 5 years! H0 = 72 ± 7 km/s/Mpc

• Looking better than ever – almost ready for a real name!

(i.e., CDM + Dark Energy + Inflation)

Precision Cosmology is Precision Cosmology is Harder than Theorists’ Harder than Theorists’

projectionsprojections

• “Bits & bites”

• l = 2 to 5

• Optical depth:

τ = 0.17 to 0.09

Serious testing of Serious testing of Inflation has Inflation has begunbegun

Key Predictions1. Flat Universe2. Almost scale-invariant, Gaussian perturbations: |(n-1)| ~ 0.1 and |dn/dlnk| ~ 0.0011. Gravity waves: spectrum, but not amplitude predicted

Key Results1. Ω0 = 1.0 ± 0.012. (n-1) = 0.96 ± 0.017*; dn/dlnk = -0.1 ± 0.05; no

evidence for nonGaussianity3. r < 0.55 (95% cl)*

*Depends significantly upon the priors assumed

Cosmic AccelerationCosmic AccelerationDark EnergyDark Energy

• Evidence for cosmic acceleration has gotten stronger (HST, CFHTLS, Essence, WMAP, XMM/Chandra…)

• Still no understanding – “theorists continue to explore phase space”

• No evidence that dark energy is not the energy of the quantum vacuum

– w = -1 ± 0.1 (from ± 0.2); no evidence for time variation

• Very significant probes on the horizon:– JDEM, LSST, …

Loose EndsLoose Ends

1. Precision test (few percent) using baryon density: BBN (D/H) vs. CMB (odd/even) unrealized

2. Consistency of BBN light element predictions (He – D – Li tension)

3. σ8: lack of consistency4. Cosmic variation of α5. Excess power at l ~ 20006. “LSND 4th neutrino”7. DAMA, e+ excess, …

What Do We Really Know What Do We Really Know About Cosmic AccelerationAbout Cosmic Acceleration

Charles A. Shapiro & Michael S. Turner,astro-ph/0512586

Much of What We Know About Much of What We Know About Cosmic Acceleration Traces to Cosmic Acceleration Traces to

Model Assumptions (Model Assumptions (ΛΛCDM, wCDM)CDM, wCDM)

• ΛCDM, wCDM are much better fits than models w/o “dark energy” (CDM or OCDM)

• … but, the acceleration history is fixed: recent acceleration, past deceleration

• In addition, the correctness of Friedmann equation is assumed (what if gravity theory is part of the solution?)

Assumptions & InputsAssumptions & Inputs

• Metric theory of gravity with Robertson-Walker metric

• “Friedmannless” analysis• Reiss et al’s Gold Set of Supernovae (adding

CFHT Legacy doesn’t change things much)• Flat Universe (can be relaxed – more later)• Piecewise constant acceleration histories• Principal component analysis for q(z)

Robust ConclusionsRobust Conclusions

• Universe may not be accelerating today: Model with deceleration since z = 0.3 is acceptable at 10% cl

• Very strong evidence that Universe once accelerated (5σ) (from best determined mode)

• Strong evidence that q(z) was larger in the past (other well determined modes)

• Weak evidence that Universe decelerated in the past

6 Most Well Determined Principal Components

Dec

eler

atio

n

Redshift

ΛCDM

2 Best Determined Modes

Without Friedmann Equation Best Without Friedmann Equation Best Evidence for Flatness is Lost Evidence for Flatness is Lost

(i.e., CMB Anisotropy)(i.e., CMB Anisotropy)

• Might be able to determine spatial curvature independently:

dV = r2drdΩ / [1 - kr2]1/2

r(z) = coordinate distance to object with redshift z|k|-1/2 = curvature radius

• Determine r and dr (e.g., SNe) and dV (e.g. number counts), infer k

My List of Burning IssuesMy List of Burning Issues

1. Cosmic Acceleration/Dark Energy: “Most Profound Mystery in all of Science”

2. Dark Matter: 3 pronged approach – space, accelerators, and underground expt’s – the prize is within sight!

3. Testing the predictions of inflation – inflation is knocking at the door to become part of “standard cosmology”

4. Using the consistency and crosschecks now afforded by precision cosmological data (BBN, SDSS/2dF, WMAP, SNe…) to test General Relativity in new regimes