Can the CMB distinguish inflation from defects?
Can the CMB distinguish inflation from defects?Yes.
Where does the 1/3 come from?1/3 = 1 - 2/3.
What about foregrounds?Observers often complain about the problems posed by foregrounds in their data. As a theorist the solution is obvious: just don't observe the foregrounds.
Which is the best experiment?It is important when answering such questions to be objective, to look at each experiment on its own merits, and not to be swayed by any personal biases. So my answer is the Balloon-borne Anisotropy Measurement at UBC, and the Low Frequency Instrument part of the Planck mission (both of which I am coincidentally involved with).