Jose Figueroa: "Topological terms and the Misner string entropy"
The method of topological renormalization in anti-de Sitter (AdS) gravity consists in adding to the action a topological term which renders it finite, defining at the same time a well-posed variational problem. Here, we use this prescription to work out the thermodynamics of asymptotically locally anti-de Sitter (AlAdS) spacetimes, focusing on the physical properties of the Misner strings of both the Taub-NUT-AdS and Taub-Bolt-AdS solutions. We compute the contribution of the Misner string to the entropy by treating on the same footing the AdS and AlAdS sectors. As topological renormalization is found to correctly account for the physical quantities in the parity preserving sector of the theory, we then investigate the holographic consequences of adding also the Chern-Pontryagin topological invariant to the bulk action; in particular, we discuss the emergence of the parity-odd contribution in the boundary stress tensor.
Martin Lagares: "Mixed boundary conditions in AdS and marginal double trace deformations of CFTs: new realizations."
I will discuss results regarding mixed boundary conditions imposed on scalar and spinor fields in AdS, and I will show how such conditions can be used to describe marginal deformations of CFTs in terms of double trace deformations. First I will talk about boundary conditions with differential operators and focus on scalar fields in AdS_{d+1}. I will present a case with directional derivatives in which only for d=1 the dual theory is a CFT for all values of the interpolating parameter. I will then discuss an alternative in which such result can be accomplished for all values of d by using a non-local operator (more precisely, the square root of the laplacian). Finally, I will talk about mixed boundary conditions which preserve supersymmetry in a N=1 theory in AdS_4 and their relation with marginal deformations of SCFTs.
Facundo Rost: "New non-perturbative de Sitter vacua in $\alpha'$-complete cosmology"
The $\alpha'$-complete cosmology developed by Hohm and Zwiebach classifies the $O(d,d;{\mathbb R})$ invariant theories involving metric, $b$-field and dilaton that only depend on time, to all orders in $\alpha'$. Some of these theories feature non-perturbative isotropic de Sitter vacua in the string frame, generated by the infinite number of higher-derivatives of $O(d,d;{\mathbb R})$ multiplets. Extending the isotropic ansatz, we construct stable and unstable non-perturbative de Sitter solutions in the string and Einstein frames. The generalized equations of motion admit new solutions, including anisotropic $d+1$-dimensional metrics and non-vanishing $b$-field. In particular, we find dS$_{n+1}\times T^{d-n}$ geometries with constant dilaton, and also metrics with bounded scale factors in the spatial dimensions with non-trivial $b$-field. We discuss the stability and possible applications of the solutions, as well as the scope of the formalism.
Leonardo Sanhuesa: "Higher Dimensional AdS Wormholes"
From the analysis of the wormhole solutions of Einstein's theory of vacuum in four dimensions with negative cosmological constant, it is possible to see that the metric sector can be generalized. Therefore, the objective of this work was to find the d-dimensional generalization and study the Kerr-NUT-AdS metrics, linking the Plebanski Deminski metrics, in different dimensions. Finally, I discuss the structure of such solutions and possible applications in supergravity.
Ricardo Stuardo: "JJbar deformations of SL(N,R) WZW Models"
The worldsheet theory on AdS3 is described by the SL(2,R) WZW model. This action admits a marginal deformation that is related to the TTbar deformation of the boundary CFT2, specifically the deformation operator is constructed as the product of Kac-Moody currents, namely JJbar. We extend this current-current deformation to higher rank groups and compute the contribution of the deformation to correlation functions.