planck cosmology 2015 the nearly exact degeneracy -- i.e., nearly the same cmb anisotropies in...
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Planck Cosmology 2015The nearly exact degeneracy -- i.e., nearly the same CMB anisotropies in models with different geometries but the same matter content –
Is a limit to deriving parameters such as the Hubble constant from CMBdata alone
It also means that an accurateindependent measure of H0 providesa key means of constraining othercosmological parameters incombination with CMB anisotropies
Ωbh2, Ωch2 well measured
CMB@50Princeton
Wendy L.FreedmanUniversityof Chicago
June 11,2015
H0
Neff
wa
w0
σ8
H0
Planck Cosmology 2015
Weinberg et al. 2012
Improvement in H0
Fiducial Stage IV prior
H0
Neff
wa
w0
H0
σ8
H0
M. Tegmark
History of the Hubble Constant
Direct Measurements of H0: Decreasing Systematics
LMCMilky Way
Δ[3.6]
ΔW
WLF et al. 2012; Scowcroft et al. 2012; Monson et al 2015WLF et al. (2001)
RIVB
M33
WLF et al. (1991
Other Future H0 Measurements:Target H0 to 1%: (sys + stat) Overcoming Systematics
LIGO Gravitational Waves
BAO
Gaia Calibration of Cepheid/RRL/SNIae
Gravitational Lens Time Delays
For robustMeasuremen,tat least 3 independentmethods withuncertaintiesat ~1% level
Landau – “Cosmologists are often in error but never in doubt”