This paper discusses some of the phenomenology of the “holographic” correspondence according to which “solving the gravitational equations of motion is dual to following the RG flow down in energy scales.” The author focuses on charged planar black holes in 4D asymptotically AdS spacetimes, corresponding to a dual quantum field theory on a background \(2+1\) Minkowski spacetime. The four main examples in this paper are described in terms of their Lagrangians: (i) Einstein-Maxwell with negative cosmological constant; (ii) the same, with a charged scalar field (“holographic superconductors”); (iii) same as (i), with a (charged) Dirac field (“electron star”); (iv) Lagrangian of (i) modified by the introduction of a “dilaton” field. The hope is that these examples provide “a controlled framework to study the low-energy physics of gapless bosons coupled to a finite density of fermions,” that would hopefully be of relevance to condensed matter physics.
For the entire collection see [Zbl 1241.83007].