Predictability crisis in inflationary cosmology and its resolution

Vanchurin, Vitaly; Vilenkin, Alexander; Winitzki, Serge

doi:10.1103/physrevd.61.083507

Cited by 87 publications

(114 citation statements)

References 32 publications

Supporting

Mentioning

112

Contrasting

Order By: Relevance

“…Following up on the approach of Refs. [8,9], we have motivated an analytic estimate for this distribution. According to Eq.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…The distribution P q (X) can in principle be determined from numerical simulations of the quantum diffusion regime. Some useful techniques for this type of simulation have been developed in [9,11,15]. However, the simulations quickly run into computational limits, due to the exponential character of the expansion.…”

Section: Probabilities Within a Pocket Universementioning

confidence: 99%

“…developed in [7,8,9,10]. It leads to the following formal expression for the probability of observations, P obs (X) ∝ P (X) n obs (X).…”

Section: Introductionmentioning

confidence: 99%

“…The purpose of the present paper is to try to improve on the approach of Refs. [7,8,9] by addressing both of these issues.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Probabilities in the inflationary multiverse

Garriga

Schwartz-Perlov

Vilenkin

et al. 2006

J. Cosmol. Astropart. Phys.

Self Cite

204

465

View full text Add to dashboard Cite

Inflationary cosmology leads to the picture of a "multiverse," involving an infinite number of (spatially infinite) post-inflationary thermalized regions, called pocket universes. In the context of theories with many vacua, such as the landscape of string theory, the effective constants of Nature are randomized by quantum processes during inflation. We discuss an analytic estimate for the volume distribution of the constants within each pocket universe. This is based on the conjecture that the field distribution is approximately ergodic in the diffusion regime, when the dynamics of the fields is dominated by quantum fluctuations (rather than by the classical drift). We then propose a method for determining the relative abundances of different types of pocket universes. Both ingredients are combined into an expression for the distribution of the constants in pocket universes of all types.

show abstract

“…Following up on the approach of Refs. [8,9], we have motivated an analytic estimate for this distribution. According to Eq.…”

Section: Summary and Discussionmentioning

confidence: 99%

Section: Probabilities Within a Pocket Universementioning

confidence: 99%

See 2 more Smart Citations

Probabilities in the inflationary multiverse

Garriga

Schwartz-Perlov

Vilenkin

et al. 2006

J. Cosmol. Astropart. Phys.

Self Cite

204

465

View full text Add to dashboard Cite

show abstract

“…This procedure has been advocated by [72,73], who applied it on the hypersurface corresponding to the end of inflation. It is easy to see that its predictions depend only on which pocket the point r lies in, not on its location within that pocket.…”

Section: Volume-based Orderingmentioning

confidence: 99%

What does inflation really predict?

Tegmark

2005

J. Cosmol. Astropart. Phys.

187

232

View full text Add to dashboard Cite

If the inflaton potential has multiple minima, as may be expected in, e.g., the string theory "landscape", inflation predicts a probability distribution for the cosmological parameters describing spatial curvature (Ωtot), dark energy (ρΛ, w, etc.), the primordial density fluctuations (Q, ns, dns/d ln k, etc.) and primordial gravitational waves (r, nt, etc.). We compute this multivariate probability distribution for various classes of single-field slow-roll models, exploring its dependence on the characteristic inflationary energy scales, the shape of the potential V and and the choice of measure underlying the calculation. We find that unless the characteristic scale ∆φ on which V varies happens to be near the Planck scale, the only aspect of V that matters observationally is the statistical distribution of its peaks and troughs. For all energy scales and plausible measures considered, we obtain the predictions Ωtot ≈ 1 ± 10 −5 , w = −1 and ρΛ in the observed ballpark but uncomfortably high. The high energy limit predicts ns ≈ 0.96, dns/d ln k ≈ −0.0006, r ≈ 0.15 and nt ≈ −0.02, consistent with observational data and indistinguishable from eternal V ∝ φ 2 inflation. The low-energy limit predicts 5 parameters but prefers larger Q and redder ns than observed. We discuss the coolness problem, the smoothness problem and the pothole paradox, which severely limit the viable class of models and measures. Predictions insensitive to pre-inflationary conditions can arise either from eternal inflation attractor behavior or from anthropic selection effects probing merely a tiny non-special part of the initial distribution. We argue that these two mechanisms are severely challenged by the coolness problem and the smoothness problem, respectively. Our findings bode well for detecting an inflationary gravitational wave signature with future CMB polarization experiments, with the arguably best-motivated single-field models favoring the detectable level r ∼ 0.03.

show abstract

Eternal Inflation and the Present Universe

Vilenkin¹

Quantum Gravity, Generalized Theory of Gravitation, and Superstring Theory-Based Unification

Self Cite

View full text Add to dashboard Cite

Eternally inflating universes can contain thermalized regions with different values of the cosmological parameters. In particular, the spectra of density fluctuations should be different, because of the different realizations of quantum fluctuations of the inflaton field. I discuss a general method for calculating probability distributions for such variable parameters and analyze the density fluctuation spectrum as a specific application.

show abstract

Predictability crisis in inflationary cosmology and its resolution

Cited by 87 publications

References 32 publications

Probabilities in the inflationary multiverse

Probabilities in the inflationary multiverse

What does inflation really predict?

Eternal Inflation and the Present Universe

Contact Info

Product

Resources

About