Pontryagin Term and Magnetic Mass in 4D AdS Gravity

Indexación: Scopus.In the context of the anti-de Sitter/Conformal Field Theory (AdS/CFT) correspondence, 4D AdS gravity is suitably renormalized by adding the Gauss Bonnet term to the Einstein-Hilbert action. The subsequent addition of the Pontryagin term, with a specific coupling, allows to write the on-shell action in terms of the Weyl tensor and its dual, such that the action becomes stationary for asymptotic (anti) self-dual solutions in the Weyl tensor. The addition to the action of both topological invariants mentioned above does not modify the bulk dynamics, but it does modify the expression of the Noether current and, therefore, the conserved quantities of the theory. Here, we show that the method of Iyer and Wald leads to a fully-covariant Noether charge, which contains both the electric and magnetic parts of the Weyl tensor. For configurations which are globally (anti) self-dual in the Weyl tensor, both the action and the Noether charge identically vanish. This means that, for such spacetimes, the magnetic mass is equal to the electric mass. © Published under licence by IOP Publishing Ltd.This work was funded in part by FONDECYT Grants No. 1131075, 1140296 and 1151107, CONICYT Grant DPI 2014-0115, UNAB Grants DI-735-15/R and DI-1336-16/RG and VRIEA-PUCV Grant 039.345/2016. R.Araneda received financial support from Facultad de Física, Pontificia Universidad Católica de Chile to participate in SOCHIFI Congress.https://iopscience.iop.org/article/10.1088/1742-6596/1043/1/01201

Implementing a signing forms mechanism in an open XMPP Server to reduce successful network attacks

Indexación: Scopus.4th School on Systems and Networks, SSN 2018; Universidad AustralValdivia; Chile; 29 October 2018 through 31 October 2018Servers implementing the eXtensible Messag-ing and Presence Protocol (XMPP) enable the near-real-time exchange of structured yet extensible data between any two or more network entities. In this paper we propose to address network attacks, a security issue, by implementing signing forms over an in-band registration mechanism. We validate our proposal implementing this mechanism over OpenFire, which is a free, community-supported and open source XMPP server. Our experiments showed that the number of successful attacks was reduced to 0 when our proposal is implemented. © 2018 CEUR-WS. All rights reserved.http://ceur-ws.org/Vol-2178/SSN2018_paper_26.pd

A study about black hole solutions with nonconstant transversal curvature and its conserved charges in Lovelock gravity

In this work, the analysis of some new static black hole solutions of Lovelock gravity with nonconstant curvature transverse section is presented. It will be shown that the finiteness of the charges and the action principle rely on the existence of constraints on the geometry of the transverse sections. Finally, in this context, some new sound solutions with nonconstant curvature transverse sections that deviate from the previously known geometries are discussed.Comment: 18 pages, No Figure

Quasinormal modes for massless topological black holes

An exact expression for the quasinormal modes of scalar perturbations on a massless topological black hole in four and higher dimensions is presented. The massive scalar field is nonminimally coupled to the curvature, and the horizon geometry is assumed to have a negative constant curvature.Comment: CECS style, 11 pages, no figures. References adde

FRW and domain walls in higher spin gravity

We present exact solutions to Vasiliev's bosonic higher spin gravity equations in four dimensions with positive and negative cosmological constant that admit an interpretation in terms of domain walls, quasi-instantons and Friedman-Robertson-Walker (FRW) backgrounds. Their isometry algebras are infinite dimensional higher-spin extensions of spacetime isometries generated by six Killing vectors. The solutions presented are obtained by using a method of holomorphic factorization in noncommutative twistor space and gauge functions. In interpreting the solutions in terms of Fronsdal-type fields in spacetime, a field-dependent higher spin transformation is required, which is implemented at leading order. To this order, the scalar field solves Klein-Gordon equation with conformal mass in (anti) de Sitter space. We interpret the FRW solution with de Sitter asymptotics in the context of inflationary cosmology and we expect that the domain wall and FRW solutions are associated with spontaneously broken scaling symmetries in their holographic description. We observe that the factorization method provides a convenient framework for setting up a perturbation theory around the exact solutions, and we propose that the nonlinear completion of particle excitations over FRW and domain wall solutions requires black hole-like states.Comment: 63 page

The horizon and its charges in the first order gravity

In this work the algebra of charges of diffeomorphisms at the horizon of generic black holes is analyzed within first order gravity. This algebra reproduces the algebra of diffeomorphisms at the horizon, (Diff(S^1)), without central extension