Has inflation fulfilled its promise?

the classical view the quantum view “ordering” “disordering”

unpredictability problem Linde, Linde, Mezhlumian, PRD 50, 2456 (1994) persistence of memory problem geodesic incompleteness entropy problem transplanckian problem

Either: - solve these problems, or - seek alternative models that avoid them Observers & experimentalists will help: - conduct tests that enable us to distinguish among inflation and its alternatives

H smoothing > H normal >> H today 1) Inflation is fast 2) Quantum physics is random

H smoothing << H normal Suppose Unpredictability Persistence of Memory Entropy Problem Singularity Problem ?

How do we go from small H to large H ? a bounce i.e., confront the singularity rather than ignore it

w ~ -1 Inflation: ultra-rapid expansion

w w >> 1 N.B. Do not need finely tuned initial conditions or inflation or dark energy … ekpyrotic/cyclic: ultra-slow contraction Erickson, Wesley, PJS. Turok Erickson, Gratton, PJS, Turok

w w >> 1 … and avoid chaotic mixmaster behavior … ekpyrotic/cyclic: slow contraction Erickson, Wesley, PJS. Turok Erickson, Gratton, PJS, Turok

w w >> 1 … and makes scale-invariant perturbations of scalar fields … ekpyrotic/cyclic: slow contraction Erickson, Wesley, PJS. Turok Erickson, Gratton, PJS, Turok

w w >> 1 … without encountering transplanckian fluctuations. ekpyrotic/cyclic: slow contraction Erickson, Wesley, PJS. Turok Erickson, Gratton, PJS, Turok

V  inflation ekpyrotic/cyclic V  Khoury, PJS, Ovrut, Turok Buchbinder, Khoury, Ovrut

“bang” radiation matter dark energy “ekpyrotic” contraction “crunch” How do we convert scalar field fluctuations into curvature perturbations?

Entropic approach: two ordinary scalar fields and NO extra dimensions: entropic  curvature Buchbinder, Khoury Ovrut, Creminelli and Senatore Koyama, Mizumo, Wands Wesley and Tolley, Finelli & Brandenberger Lehners, McFadden, Turok, and PJS AdS/CFT approach: (see Turok’s talk) Turok, Craps, Hertog

Gravitational waves? Non-gaussian fluctuations?

Gravitational waves? Non-gaussian fluctuations? Primordial amplitude proportional to H smoothing 2

from Baumann, PJS, Takahashi, Ichiki see also Mollerach, Harari, Mattarese Ananda, Clarkson, Wands

Gravitational waves? Non-gaussian fluctuations?

Buchbinder, Khoury Ovrut, arXiv: Creminelli and Senatore, hep-th/ Koyama, Mizumo, Wands, to appear Entropic mechanism can produce significant non-gaussianity: (WMAP team) (Yadav & Wandelt) compatible for w < 30 conversion during ekpyrotic phase

J-L. Lehners & PJS Entropic mechanism can produce significant non-gaussianity: (WMAP team) conversion after ekpyrotic phase compatible for w < 3000 and with tilt (Yadav & Wandelt)

(WMAP team) (Yadav & Wandelt)