3. Great explanatory power: horizon – flatness – monopoles – entropy Great predictive power:  total = 1 nearly scale-invariant perturbations slightly red tilt adiabatic gaussian gravitational waves consistency relations - ? ? ?

4. “the classic(al) perspective” dominantly a classical process… an ordering process… in which quantum physics plays a small but important perturbative role

5. “the (true) quantum perspective” Inflation is dominantly a quantum process… in which (classical) inflation amplifies rare quantum fluctuations… resulting in a peculiar kind of disorder

6. Eternal Inflation Vilenkin, 1983 PJS, 1983

7. “I would argue that once one accepts eternal inflation as a logical possibility, then there is no contest in comparing an eternally inflating version of inflation with any theory that is not eternal....” Alan Guth, 2000

8. Powerfully predictive? Linde, Linde, Mezhlumian, PRD 50, 2456 (1994)

9. SINGULARITY PROBLEM cf. Borde and Vilenkin, PRL 72, 3305 (1994); PRD 56, 717 (1997) If Eternal to the Past, then maybe we can uniquely determine the probabilities.

10. Maybe can find measure that does not depend on initial conditions Global vs. Local Measures?

11. Immune from initial conditions?

12. Important properties insensitive to initial conditions? Garriga, Guth and Vilenkin, hep-th/0612242 Aguirre, Johnson and Shomer, arxiv:0704.3473 Chang, Kleban, Levi, arxiv:07012.2261 Aguirre, Johnson, arxiv:0712.3038  initial “Persistence of Memory Effect”

13.  YELLOW: anisotropic! Important properties insensitive to initial conditions?

14. Perhaps we know the Iniitial Condiions?? Entropy Problem: requires entropically disfavored initial state? Penrose

15. Singularity problem Unpredictability problem Persistence of memory Entropy problem theory incomplete ? threatens flatness and scale invariance? threatens isotropy? advantage  problem “the (true) quantum perspective”

17. energy density large or H smoothing > H normal >> H today 1) Inflation is fast 2) Quantum physics is random Singularity problem Unpredictability problem Persistence of memory Entropy problem “the (true) quantum perspective”

18. Singularity problem Unpredictability problem Persistence of memory Entropy problem “the (true) quantum perspective” H smoothing << H normal But suppose

19. How do we go from small H to large H ? H smoothing contracting implies must resolve singularity problem

20. Ekpyrotic model “ekpyrotic contraction” bounce radiation Cyclic model “ekpyrotic contraction” bounce radiation matter dark energy......

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

22. w … and avoid chaotic mixmaster behavior … ekpyrotic phase: ultra-slow contraction with w >>1 Erickson, Wesley, PJS. Turok Erickson, Gratton, PJS, Turok w >> 1

23. w … and H smoothing << H normal and contracting ekpyrotic phase: ultra-slow contraction with w >>1 Erickson, Wesley, PJS. Turok Erickson, Gratton, PJS, Turok w >> 1

24. w … and scale-invariant perturbations of scalar fields. ekpyrotic phase: ultra-slow contraction with w >>1 Erickson, Wesley, PJS. Turok Erickson, Gratton, PJS, Turok w >> 1

25. How to get w >> 1 ? V  Field-theory “branes” 

26. H smoothing is exponentially different w is orders of magnitude different Curiously, precision tests can distinguish the two key qualitative differences between inflation and ekpyrotic/cyclic models gravitational waves local non-gaussianity

27. “local” non-gaussianity generated when modes are outside the horizon (“local” NG)  =  L + f NL  L 2 3 5 Maldacena Komatsu & Spergel “intrinsic” NG contribution (positive f NL ) depending on  = (1 + w) or steepness of potential 3 2