I will start with an overview of various recent developments in the area of higher-order gravities and their black hole solutions, which have led to the discovery of a new type of theories which generalize the Lovelock class. Then, I will focus on Einsteinian cubic gravity (ECG) which, in a sense I will make precise, provides a canonical modification of Einstein gravity in D=4, analogous to the one produced by Gauss-Bonnet in D>4. I will discuss two applications. Firstly, I will explain how ECG (and its cousin theories) drastically modify the evaporation process of black holes. And second, I will show that ECG provides a non-perturbative toy-model for a non-supersymmetric holographic CFT (analogous to Quasi-topological gravity in d=4) in three (boundary) dimensions and discuss some of its properties.

Dimensional reduction of supergravity theories on spheres plays a central role in the gauge/gravity correspondence. Prominent examples are the reductions of eleven-dimensional supergravity on S7 and type IIB supergravity on S5 which are dual to ABJM and N=4 SYM theories, respectively. Using the recently discovered duality between massive IIA supergravity on S6 and super Chern-Simons-matter theories, we will describe RG flows holographically in terms of domain-wall and black hole solutions in the gravity side.

The problem of quantizing gravitational interactions is related to the non-renormalizability of the Einstein-Hilbert action and the need to include and infinite number of order one operators at energies of about the Planck scale. This has been interpreted as suggesting the existence of new physics at (or below) this scale, which may relax the strong coupling regime, leading to an ultra-violet complete theory. Here I will take a different approach — the possibility that gravity might undergo a strong coupling phase for a finite range of energies, eventually going back to a weakly coupled theory with a different symmetry realization, represented by the ultra-violet complete version of Hořava gravity.

Dear theoretical physicists, The last edition of the holographic party was nice but once again the phonons didn't come and there was no music. We all know whose fault it is. So my proposal for this year is simple: let's not invite Lorentz. He has his temper so we should do it in a non-explicit way. From past experiences we know that this is a non-trivial task, however I must remark that this is an absolute must if we want to come close to something which actually looks like a real party. Lately some people have been proposing a class of massive gravity holographic models which do the job, I think we should try. It's about time.

It is known that not every effective field theory could be embedded in quantum gravity, but only those which are consistent with the QG conjectures. Does these constraints have an impact in low energy physics? Recently, Ooguri and Vafa argued using a strong approach of the Weak Gravity Conjecture that non-supersymmetric stable AdS vacua are incompatible with quantum gravity. It is also known that compactifying the Standard Model to 3 or 2 dimensions can give rise to AdS vacua. Using the fact that those vacua must be absent, several constraints are set on the SM and BSM particles, obtaining a lower bound on the cosmological constant in terms of the masses of the neutrinos. Moving forward one can translate those into an upper bound for the EW scale around the TeV range.

Consistency with quantum gravity and black hole physics puts significant constraints on low-energy effective field theories. In fact, most EFT’s do not satisfy these criteria, and are said to be in the “Swampland”. Most Swampland constraints remain conjectural, supported mainly by a plethora of stringy examples. In this talk I will discuss a better supported example of a Swampland constraint, in the context of the AdS/CFT correspondence: A bound on the gauge coupling of any U(1) theory coupled to gravity in AdS space. This equivalent to a bound on the two-point coefficient of holographic large N theories. The same logic leads to a logarithmic bound involving the gauge coupling, the cutoff of the effective field theory, the AdS radius, and Planck’s mass.

Microstate geometries are horizonless solitonic solutions of supergravity theories which have been claimed to correspond to the classical description of particular microstates of a given black hole. Such solutions are sourced by charges "dissolved in fluxes" threading non-contractible cycles, and for this reason the construction of explicit generic examples has remained a challenging problem for more than a decade. In this talk I will present the results of arXiv:1709.03985, where a strategy to sistematically construct all (symmetric) microstate geometries is proposed.

Known N=4 theories in four dimensions are characterized by a choice of gauge group, and in some cases some "discrete theta angles", as classified by Aharony, Seiberg and Tachikawa. I will review how this data, for the theories with algebra su(N), is encoded in various familiar realizations of the theory, in particular in the holographic AdS_5 \times S^5 dual and in the compactification of the (2,0) A_N theory on T^2. I will then show how the resulting structure, given by a choice of polarization of an appropriate cohomology group, admits additional choices that, unlike known theories, generically preserve SL(2,Z) invariance in four dimensions.

I will explain the classification of bundles of weakly faithful Clifford modules in terms of Lipschitz structures. As an application, I will prove that, in the presence of an internal Dirac operator, M theory can only be defined on orientable and spin eleven-dimensional manifolds. This is work in collaboration with C. Lazaroiu.

I will discuss one loop corrections to the entropy of Reissner-Nordstrom extremal black holes induced by charged massive particles. When the particles are super-extremal, IR divergences in the computation reflect the instability of the black hole against Schwinger pair production and decay. When super-extremal particles are absent extremal, black holes are stable and charged particles can induce interesting logarithmic corrections to their entropy. I will suggests possible connections to the Weak Gravity Conjecture, which demands the existence of (super-)extremal particles.