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abstract

Causal Dynamical Triangulations (CDT) is a lattice theory of quantum gravity. It is shown how to identify the IR and the UV limits of this lattice theory with similar limits studied using the continuum, functional renormalization group (FRG) approach. The main technical tool in this study will be the so-called two-point function. It will allow us to identify a correlation length not directly related to the propagation of physical degrees of freedom.

abstract

This is a review of gravitational instantons — solutions to Riemannian Einstein or Einstein–Maxwell equations in four dimensions which yield complete metrics on non-compact four-manifolds, and which asymptotically ‘look like’ flat space. The review focuses on examples, and is based on lectures given by the author at the Cracow School of Theoretical Physics held in Zakopane in June 2024.