UMICH-2015: Inflation break-out session 3
"Milestones for Inflation and Alternative models"
Categories of inflation science
(A) The implications of a detection of primordial gravitational waves (B) Continued refinement of constraints on the inflationary model space (standard stuff, but not contingent on detecting prim. grav. waves) and on presence of other light particles during inflation (C) Science that, depending on your politics, either addresses a lurking discomfort about inflation as a predictive theory, or, explores the exciting implications of the mulit-verse (not contingent on detecting prim. grav. waves)
(A) The implications of a detection of primordial gravitational waves
(1) The usual stuff about what a detection of r would mean: - detection would rule out the only currently developed competitor to inflation (ekpyrotic scenario) - detection would determine the scale of inflation (caveat below) - large field vs small field: detection above the large field threshold implies an (approximate) symmetry of quantum gravity (caveat below) - detection provides strong evidence for (linearized) quantum gravity (caveat below)
(2) In the event of a detection, what are the important additional questions? (ie, what else would we want to be sure to be able to measure optimally?) Address caveats to the claims in (1): * slide: Scott Watson Media:scott.pdf - what is the reheating temp? (Is it large field with high T(reheat), or small field with low T(reheat)?) - are we sure it's the quantum fluctuations from large field inflation: eg, distinguish GW from particle production during inflation; distinguish cases where epsilon varies a lot (so maybe not really large field); anything else to contrast, no matter how contrived it may look? - related specifics of the tensor sector: how well could we bound n_T, and any non-Gaussianity in the tensor sector (or correlations between tensors and scalars)? Consider complementarity with next and next-next generation direct searches for stochastic GW background?
(3) In the event of a detection, what else can we hope to learn from the tensor sector? - same specific data as above: n_T and NG. NG as a probe of QG. - pseudo-scalar (axion monodromy models) vs scalar inflaton (Csaki et al 1406.5192)
(B) Continued refinement of constraints on the inflationary model space break-out 2
- with a detection of r (including constraints on other light fields, c_s) - not contingent on a detection of r * is fnl local ~ 1 the right threshold (slide: Joel Meyers) * resonant NG (slide: Daan Meerburg Media:daan.pdf) - would we be willing to sacrifice some parameter space in r to do better on, say, NG?
(C) Other science addressing the nature of inflation:
- Using kSZ to search for evidence of bubble collisions (slide: Matt Johnson, 1501.00511 Media:matt_ksz_slide.pdf, needs large sky coverage) - Any evidence that our current Hubble scale is special (a violation of the cosmological principle)? eg, inflation had a minimal number of e-folds; evidence of non-BD or some other distinct departure from SR inflation; Anomalies? Bulk flows? Features of power spect. or NG? (Note: predictions of polarization signals based on LCDM/TT signals in Yoho etal ) - Slightly different take on NG: Any evidence of significant long-short mode-coupling (eg, is unknown super-horizon stuff is a source of cosmic variance? Or, theories are theories of last ~55 e-folds only: initial conditions problem of inflation?)
The measurement goals to support the theory
(A1) What is required to achieve ?
Essentially snowmass figures 2 and 3: what updates/changes are needed?
(B) What is required to make significant progress in constraining inflation model space even if there is no detection of primordial grav waves?
(C) What is required to address more speculative inflation science?
- Can kSZ be used to access more large scale information - any handles on non-Gaussianity from secondary CMB combined with other surveys? Rather than full n-point functions, test for eg any position dependence in power spectrum, pos. dependent equil. bispect., ... break-out 2 - How much will polarization + kSZ + ??? affect significance of "anomalies" break-out 2