Extension of the Poincar\'e group with half-integer spin generators: hypergravity and beyond

An extension of the Poincar\'e group with half-integer spin generators is explicitly constructed. We start discussing the case of three spacetime dimensions, and as an application, it is shown that hypergravity can be formulated so as to incorporate this structure as its local gauge symmetry. Since the algebra admits a nontrivial Casimir operator, the theory can be described in terms of gauge fields associated to the extension of the Poincar\'e group with a Chern-Simons action. The algebra is also shown to admit an infinite-dimensional non-linear extension, that in the case of fermionic spin-$3/2$ generators, corresponds to a subset of a contraction of two copies of WB$_2$. Finally, we show how the Poincar\'e group can be extended with half-integer spin generators for $d\geq3$ dimensions.Comment: 12 pages, no figures. Matches published versio

Asymptotic structure of N=2\mathcal{N}=2 supergravity in 3D: extended super-BMS3_3 and nonlinear energy bounds

The asymptotically flat structure of $\mathcal{N}=(2,0)$ supergravity in three spacetime dimensions is explored. The asymptotic symmetries are spanned by an extension of the super-BMS$_3$ algebra, with two independent $\hat{u}(1)$ currents of electric and magnetic type. These currents are associated to $U(1)$ fields being even and odd under parity, respectively. Remarkably, although the $U(1)$ fields do not generate a backreaction on the metric, they provide nontrivial Sugawara-like contributions to the BMS$_3$ generators, and hence to the energy and the angular momentum. The entropy of flat cosmological spacetimes with $U(1)$ fields then acquires a nontrivial dependence on the $\hat{u}(1)$ charges. If the spin structure is odd, the ground state corresponds to Minkowski spacetime, and although the anticommutator of the canonical supercharges is linear in the energy and in the electric-like $\hat{u}(1)$ charge, the energy becomes bounded from below by the energy of the ground state shifted by the square of the electric-like $\hat{u}(1)$ charge. If the spin structure is even, the same bound for the energy generically holds, unless the absolute value of the electric-like charge is less than minus the mass of Minkowski spacetime in vacuum, so that the energy has to be nonnegative. The explicit form of the Killing spinors is found for a wide class of configurations that fulfills our boundary conditions, and they exist precisely when the corresponding bounds are saturated. It is also shown that the spectra with periodic or antiperiodic boundary conditions for the fermionic fields are related by spectral flow, in a similar way as it occurs for the $\mathcal{N}=2$ super-Virasoro algebra. Indeed, our super-BMS$_3$ algebra can be recovered from the flat limit of the superconformal algebra with $\mathcal{N}=(2,2)$, truncating the fermionic generators of the right copy.Comment: 32 pages, no figures. Talk given at the ESI Programme and Workshop "Quantum Physics and Gravity" hosted by ESI, Vienna, June 2017. V3: minor changes and typos corrected. Matches published versio

Disrupting Risk Governance? A Post-Disaster Politics of Inclusion in the Urban Margins

Facing climate emergency and disaster risks, cities are developing governing arrangements towards sustainability and resilience. Research is showing the ambivalent results of these arrangements in terms of inclusion and (in)justice, as well as their outcomes in emptying the ‘properly political’ through depoliticised governing techniques. Acknowledging this post-political thesis, however, critical analyses must also engage with re-politicization and focus on disruptive and transformative governance efforts. This article addresses the dual dynamics of de—and re-politicisation, focusing on the interplay of different modes of governing urban risk. We follow the political philosophy of Jacques Rancière and related interpretations in critical urban studies to recover the politics of the city. We focus on a post-disaster area in the foothills of Santiago, Chile. After a 1993 disaster, the State constituted a mode of governing risks based on physicalist interventions that discouraged local conflicts. This techno-managerial policing order made risks invisible while favouring real estate development. However, we show how local initiatives emerge in the interstices of formal and informal arrangements that contest this course. This emerging mode of governing risk, we argue, has the potential to recover incrementally urban politics and disrupt the dominant one through an egalitarian principle on the margins. Our contribution shows that, although these modes of governance coexist and are still evolving, advancing more just and inclusive cities require moving beyond consensus-based governance and focusing on the role of dissent and disruptive politics

Hypergravity in five dimensions

We show that a spin-$5/2$ field can be consistently coupled to gravitation without cosmological constant in five-dimensional spacetimes. The fermionic gauge "hypersymmetry" requires the presence of a finite number of additional fields, including a couple of $U(1)$ fields, a spinorial two-form, the dual of the graviton (of mixed $(2,1)$ Young symmetry) and a spin-$3$ field. The gravitational sector of the action is described by the purely quadratic Gauss-Bonnet term, so that the field equations for the metric are of second order. The local gauge symmetries of the full action principle close without the need of auxiliary fields. The field content corresponds to the components of a connection for an extension of the "hyper-Poincar\'e" algebra, which apart from the Poincar\'e and spin-$3/2$ generators, includes a generator of spin $2$ and a $U(1)$ central extension. It is also shown that this algebra admits an invariant trilinear form, which allows to formulate hypergravity as a gauge theory described by a Chern-Simons action in five dimensions.Comment: 17 pages, no figures, minor changes, references adde

Planning for Exclusion: The Politics of Urban Disaster Governance

Many disaster risk reduction (DRR) initiatives, including land use planning, tend to ignore existing long-term inequalities in urban space. Furthermore, scholars working on urban disaster governance do not adequately consider how day-to-day DRR governing practices can (re)produce these. Hence, following a recent interest in the political dimensions of disaster governance, this article explores under what conditions the implementation of DRR land uses (re)produce spatial injustice on the ground. We develop a theoretical framework combining politics, disaster risk, and space, and apply it to a case study in Santiago, Chile. There, after a landslide disaster in the city’s foothills in 1993, a multi-level planning arrangement implemented a buffer zone along the bank of a ravine to protect this area from future disasters. This buffer zone, however, transformed a long-term established neighbourhood, splitting it into a formal and an informal area remaining to this day. Using qualitative data and spatial analysis, we describe the emergence, practices, and effects of this land use. While this spatial intervention has proactively protected the area, it has produced further urban exclusion and spatial deterioration, and reproduced disaster risks for the informal households within the buffer zone. We explain this as resulting from a governance arrangement that emerged from a depoliticised environment, enforcing rules unevenly, and lacking capacities and unclear responsibilities, all of which could render DRR initiatives to be both spatially unjust and ineffective. We conclude that sustainable and inclusive cities require paying more attention to the implementation practices of DRR initiatives and their relation to long-term inequities

Integrable systems with BMS3_{3} Poisson structure and the dynamics of locally flat spacetimes

We construct a hierarchy of integrable systems whose Poisson structure corresponds to the BMS$_{3}$ algebra, and then discuss its description in terms of the Riemannian geometry of locally flat spacetimes in three dimensions. The analysis is performed in terms of two-dimensional gauge fields for $isl(2,R)$. Although the algebra is not semisimple, the formulation can be carried out \`a la Drinfeld-Sokolov because it admits a nondegenerate invariant bilinear metric. The hierarchy turns out to be bi-Hamiltonian, labeled by a nonnegative integer $k$, and defined through a suitable generalization of the Gelfand-Dikii polynomials. The symmetries of the hierarchy are explicitly found. For $k\geq 1$, the corresponding conserved charges span an infinite-dimensional Abelian algebra without central extensions, and they are in involution; while in the case of $k=0$, they generate the BMS$_{3}$ algebra. In the special case of $k=1$, by virtue of a suitable field redefinition and time scaling, the field equations are shown to be equivalent to a specific type of the Hirota-Satsuma coupled KdV systems. For $k\geq 1$, the hierarchy also includes the so-called perturbed KdV equations as a particular case. A wide class of analytic solutions is also explicitly constructed for a generic value of $k$. Remarkably, the dynamics can be fully geometrized so as to describe the evolution of spacelike surfaces embedded in locally flat spacetimes. Indeed, General Relativity in 3D can be endowed with a suitable set of boundary conditions, so that the Einstein equations precisely reduce to the ones of the hierarchy aforementioned. The symmetries of the integrable systems then arise as diffeomorphisms that preserve the asymptotic form of the spacetime metric, and therefore, they become Noetherian. The infinite set of conserved charges is recovered from the corresponding surface integrals in the canonical approach.Comment: 34 pages, 2 figure

Gravity coupled to a scalar field from a Chern-Simons action: describing rotating hairy black holes and solitons with gauge fields

Einstein gravity minimally coupled to a scalar field with a two-parameter Higgs-like self-interaction in three spacetime dimensions is recast in terms of a Chern-Simons form for the algebra $g^{+}\oplus g^{-}$ where, depending on the sign of the self-interaction couplings, $g^{\pm}$ can be $so(2,2)$, $so(3,1)$ or $iso(2,1)$. The field equations can then be expressed through the field strength of non-flat composite gauge fields, and conserved charges are readily obtained from boundary terms in the action that agree with those of standard Chern-Simons theory for pure gravity, but with non-flat connections. Regularity of the fields then amounts to requiring the holonomy of the connections along contractible cycles to be trivial. These conditions are automatically fulfilled for the scalar soliton and allow to recover the Hawking temperature and chemical potential in the case of the rotating hairy black holes presented here, whose entropy can also be obtained by the same formula that holds in the case of a pure Chern-Simons theory. In the conformal (Jordan) frame the theory is described by General Relativity with cosmological constant conformally coupled to a self-interacting scalar field, and its formulation in terms of a Chern-Simons form for suitably composite gauge fields is also briefly addressed.Comment: 23 pages, no figure

Estudio genómico de cepas argentinas de Herpesvirus equino 1

La infección por Herpesvirus equino 1 (EHV-1) tiene un significativo impacto económico en la producción equina mundial al causar abortos, enfermedad respiratoria, muertes perinatales y desórdenes neurológicos. La identificación de genes específicos relacionados con la virulencia y patogenicidad de este virus ha sido el propósito de varios grupos de investigación. En este trabajo se analizaron diferentes regiones genómicas de cepas argentinas de EHV-1 para determinar la posible relación entre la estructura genómica y la virulencia o los signos clínicos producidos. Veinticinco cepas aisladas de diferentes casos clínicos observados entre los años 1979 y 2007 y dos cepas de referencia fueron amplificadas y secuenciadas. El alineamiento de las secuencias se realizó con el programa Clustal X versión 1.92; el programa Bio-Edit versión 7.05 permitió deducir la secuencia de aminoácidos. Solo se observaron cambios menores, no se encontraron variaciones que pudieran estar relacionadas con la diferencia de virulencia observada previamente en el modelo ratón. No se hallaron variantes genómicas. Las regiones genómicas analizadas no permitieron diferenciar cepas abortigénicas de aquellas aisladas de muertes neonatales.Equid herpesvirus 1 (EHV-1) infection has a significant economic impact on equine production, causing abortion, respiratory disease, neonatal death and neurological disorders. The identification of specific EHV-1 genes related to virulence and pathogenicity has been the aim of several research groups. The purpose of the present study was to analyze different genomic regions of Argentinean EHV-1 strains and to determine their possible relationship with virulence or clinical signs. Twenty-five EHV-1 Argentinean isolates recovered from different clinical cases between 1979 and 2007 and two reference strains were amplified and sequenced. The sequence alignments were carried out using Clustal X version 1.92 and the putative amino acid sequences were deduced using Bio-Edit version 7.05. Minor changes were observed. No changes that could be involved in the different virulence in the mouse model of three EHV-1 Argentinean strains were found. No genetic variants were observed. The genomic regions analyzed are unsuitable for differentiation between abortigenic strains and those isolated from neonatal deaths.Fil: Fuentealba, Nadia Analia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Departamento de Microbiología. Cátedra de Virología; ArgentinaFil: Sguazza, Guillermo Hernán. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Departamento de Microbiología. Cátedra de Virología; ArgentinaFil: Eöry, Matías Leonel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Departamento de Microbiología. Cátedra de Virología; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Departamento de Ciencias Básicas. Cátedra de Histología y Embriología; ArgentinaFil: Valera, Alejandro Rafael. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Departamento de Microbiología. Cátedra de Virología; ArgentinaFil: Pecoraro, Marcelo Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Departamento de Microbiología. Cátedra de Virología; ArgentinaFil: Galosi, Cecilia Monica. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Departamento de Microbiología. Cátedra de Virología; Argentin