In this paper (https://arxiv.org/abs/hep-th/0211048) by physicist Andrei Linde, the multiverse concept, the anthropic principle, quantum cosmology and inflationary cosmology are analyzed.
In the paper, he analyzes a multiverse with a large landscape of universes (described by different spaces and dimensions, different lagrangians, different actions, different types of evolution…)
He mentions and analyzes various models of theoretical physics (like inflation cosmology, quantum cosmology, Wheeler-DeWitt equation…) but does not clarify whether any of these models could be applied to the vast multiverse he is describing. He neither does specify which of these models could produce such variety of hypothetical universes nor if any of them could produce it.
So my question is:
Is it there any theory/model/equation that could produce such a vast multiverse? Any model that Linde mentions? Could Wheeler-DeWitt equation be an option for that?
Linde suggested that Wheeler's "it from bit" could contain such universe. Since there are loop quantum gravity models which are based on this idea, this could be an option...But apart from this, is it there any other model/theory?
In summary, is it there any theory/model/equation (apart from loop quantum gravity models) that could produce all the universes studied by Linde and proposed by certain versions of the anthropic principle (https://en.wikipedia.org/wiki/Anthropic_principle)?