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Page 1: COMING HOME

COMING HOMECOMING HOME

Michael S. Turner

Kavli Institute for Cosmological Physics

The University of Chicago

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Some Cosmological Some Cosmological Observations from AfarObservations from Afar

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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)

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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

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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

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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, …

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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, …

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

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

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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?)

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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)

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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

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6 Most Well Determined Principal Components

Dec

eler

atio

n

Redshift

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ΛCDM

2 Best Determined Modes

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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

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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