317 research outputs found
Chern-Simons Supergravities with Off-Shell Local Superalgebras
A new family of supergravity theories in odd dimensions is presented. The
Lagrangian densities are Chern-Simons forms for the connection of a
supersymmetric extension of the anti-de Sitter algebra. The superalgebras are
the supersymmetric extensions of the AdS algebra for each dimension, thus
completing the analysis of van Holten and Van Proeyen, which was valid for N=1
and for D=2,3,4,mod 8. The Chern-Simons form of the Lagrangian ensures
invariance under the gauge supergroup by construction and, in particular, under
local supersymmetry. Thus, unlike standard supergravity, the local
supersymmetry algebra closes off-shell and without requiring auxiliary fields.
The Lagrangian is explicitly given for D=5, 7 and 11. In all cases the
dynamical field content includes the vielbein, the spin connection, N
gravitini, and some extra bosonic ``matter'' fields which vary from one
dimension to another. The superalgebras fall into three families: osp(m|N) for
D=2,3,4, mod 8, osp(N|m) for D=6,7,8, mod 8, and su(m-2,2|N) for D=5 mod 4,
with m=2^{[D/2]}. The possible connection between the D=11 case and M-Theory is
also discussed.Comment: 13pages, RevTeX, no figures, two column
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- generators, corresponds to a subset of a contraction of two copies
of WB. Finally, we show how the Poincar\'e group can be extended with
half-integer spin generators for dimensions.Comment: 12 pages, no figures. Matches published versio
Asymptotic structure of supergravity in 3D: extended super-BMS and nonlinear energy bounds
The asymptotically flat structure of supergravity in
three spacetime dimensions is explored. The asymptotic symmetries are spanned
by an extension of the super-BMS algebra, with two independent
currents of electric and magnetic type. These currents are associated to
fields being even and odd under parity, respectively. Remarkably, although the
fields do not generate a backreaction on the metric, they provide
nontrivial Sugawara-like contributions to the BMS generators, and hence to
the energy and the angular momentum. The entropy of flat cosmological
spacetimes with fields then acquires a nontrivial dependence on the
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
charge, the energy becomes bounded from below by the energy of the
ground state shifted by the square of the electric-like 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
super-Virasoro algebra. Indeed, our super-BMS algebra can
be recovered from the flat limit of the superconformal algebra with
, 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
Canonical sectors of five-dimensional Chern-Simons theories
The dynamics of five-dimensional Chern-Simons theories is analyzed. These
theories are characterized by intricate self couplings which give rise to
dynamical features not present in standard theories. As a consequence, Dirac's
canonical formalism cannot be directly applied due to the presence of
degeneracies of the symplectic form and irregularities of the constraints on
some surfaces of phase space, obscuring the dynamical content of these
theories. Here we identify conditions that define sectors where the canonical
formalism can be applied for a class of non-Abelian Chern-Simons theories,
including supergravity. A family of solutions satisfying the canonical
requirements is explicitly found. The splitting between first and second class
constraints is performed around these backgrounds, allowing the construction of
the charge algebra, including its central extension.Comment: 12 pages, no figure
Exact quasinormal modes for a special class of black holes
Analytic exact expressions for the quasinormal modes of scalar and
electromagnetic perturbations around a special class of black holes are found
in d\ge3 dimensions. It is shown that, the size of the black hole provides a
bound for the angular momentum of the perturbation. Quasinormal modes appear
when this bound is fulfilled, otherwise the excitations become purely damped.Comment: 8 pages, no figures. Slightly updated version of the plenary talk
given at the General Relativity Conference: "50 Years of FaMAF and Workshop
on Global Problems in Relativity", hosted during November 2006 at FaMAF,
Universidad Nacional de Cordoba, Cordoba, Argentina
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