An interesting paper just appeared on arxiv today. http://arxiv.org/abs/1009.3741 Identifying the Inflaton Damien A. Easson, Brian A. Powell 5 pages, 2 figures (Submitted on 20 Sep 2010) "We explore the ability of experimental physics to uncover the underlying structure of the gravitational Lagrangian responsible for inflation. It is a common expectation that improved measurements of the primordial perturbations will result in a better understanding of the nature of the inflaton field. We investigate to what extent this expectation is justifiable within the context of a general inflationary Lagrangian. Our conclusion is that observables beyond the adiabatic and tensor two-point functions on CMB scales are needed; in particular, isocurvature modes or a combination of local non-Gaussiantities and a precision measurement of the tensor spectral index will enable the most successful reconstructions. We show that amongst these observables, the most powerful probe of the inflationary Lagrangian is a precision measurement of the tensor spectral index, as might be possible with a direct detection of primordial gravitational waves." I don't have time to comment now but it is always interesting to hear discussion of what it is and is not possible to learn empirically about the early universe (from examining its traces in the CMB). We know of Easson in part because of a couple of papers he published this past year with Nobelist George Smoot (about entropic force in cosmology---how it might have a role in understanding either inflation or the present accelerated expansion.) I think of him as doing serious and original work, and willing to take some chances: win or lose. Just a superficial impression but it means I'm moderately alert when I see a new paper by him. Maybe someone else will evaluate this and comment.