PPPDT Feb 27: ‘unofficial’ response to

questions

Lawrence Krauss

CWRU

Positive B-modes?

• Something happening close to GUT scale!

• If inflation: points to perturbative power series single field potentials (dominated by m^2 phi^2 term) with large values of phi.

• BUT: NOT AN UNAMBIGUOUS SIGNAL OF INFLATION. (KJS,LMK,HM (PRL, in press))

EX: O(N) Phase Transition

• Causality implies GW spectrum generated on the horizon at all times (LMK, ‘92)

• Exact calculation much bigger than naïve estimate:

Small r?

• Important constraint: validates smaller than M_pl field variation.

• Note: expectation value of r depends upon priors. (LMK, WV ‘08, prelim)

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Conclusions

• Whether r is small or large, we learn a great deal.. I do not believe we are likely to be able to unambiguously infer the existence or nature of inflation.. But a B-mode mission will directly probe the GUT scale and quantitative physics in a way that Dark Energy mission is not likely to, for example.