Континуальный предел спиновой пены — это ОТО?

I will present first results on the continuum limit of spin foams, which allow for a new phenomenological approach, based on continuum quantum field theory. Spin foams are discretized path integrals for quantum gravity based on a rigorous definition of quantum geometry. This does however lead to very complicated amplitudes, making e.g. the extraction of a continuum limit difficult. Thus, a long-standing open question was whether spin foams do describe gravity in their semi-classical and continuum limit. The situation has changed with the recent introduction of effective spin foams, which on the one hand are much more amenable to numerical simulations, but also offer a much more transparent encoding of the dynamics. This has allowed first systematics results on the continuum limit, revealing that this limit is described by an area metric (instead of a length metric) dynamics. The space of area metric configurations represents an extension of the length metric space. This extension results from the quantum geometric input and is controlled by the Barbero-Immirzi parameter and the Planck lenghts. Integrating out these additional quantum degrees of freedom we obtain an effective action of the length metric, given by the Einstein-Hilbert term and a Weyl-squared term. This results can be confirmed by an independent construction, that works entirely in the continuum, and is based on a modification of the Plebanski formulation of Gravity.