- The current limit \( r < 0.035 \) (95% CL) does not contradict the model predictions.
- Non-Gaussianities:
- Planck's result \( f_{\text{NL}}^{\text{local}} = -0.9 \pm 5.1 \) is consistent with the prediction \( f_{\text{NL}} \sim \mathcal{O}(1) \).
Observation Consistency Table:
| Parameters|Model Predictions|Observation Results|Consistency|
| \( r \) | \( \sim 0.003 \) | \( < 0.056 \) (Planck) | |
| \( n_s \) | \( 0.965 \) | \( 0.9649 \pm 0.0042 \) | |
| \( f_{\text{NL}} \) | \( \mathcal{O}(1) \) | \( -0.9 \pm 5.1 \) | |
5.2 Criticism and Challenges
5.2.1 The Measure Problem in the Multiverse
- Description: In an infinite multiverse, there is no unique way to calculate the relative probability of a bubble universe with a given . Results depend on the selection of cut-off (Vilenkin, 2007; Guth, 2015).
