140 research outputs found
IIB solutions with N>28 Killing spinors are maximally supersymmetric
We show that all IIB supergravity backgrounds which admit more than 28
Killing spinors are maximally supersymmetric. In particular, we find that for
all N>28 backgrounds the supercovariant curvature vanishes, and that the
quotients of maximally supersymmetric backgrounds either preserve all 32 or
N<29 supersymmetries.Comment: 27 page
Gauging the Wess-Zumino term of a sigma model with boundary
We investigate the gauging of the Wess-Zumino term of a sigma model with
boundary. We derive a set of obstructions to gauging and we interpret them as
the conditions for the Wess-Zumino term to extend to a closed form in a
suitable equivariant relative de Rham complex. We illustrate this with the
two-dimensional sigma model and we show that the new obstructions due to the
boundary can be interpreted in terms of Courant algebroids. We specialise to
the case of the Wess-Zumino-Witten model, where it is proved that there always
exist suitable boundary conditions which allow gauging any subgroup which can
be gauged in the absence of a boundary. We illustrate this with two natural
classes of gaugings: (twisted) diagonal subgroups with boundary conditions
given by (twisted) conjugacy classes, and chiral isotropic subgroups with
boundary conditions given by cosets.Comment: 18 pages (minor changes in response to referee report
N=31, D=11
We show that eleven-dimensional supergravity backgrounds with thirty one
supersymmetries, N=31, admit an additional Killing spinor and so they are
locally isometric to maximally supersymmetric ones. This rules out the
existence of simply connected eleven-dimensional supergravity preons. We also
show that N=15 solutions of type I supergravities are locally isometric to
Minkowski spacetime.Comment: 17 page
The return of the four- and five-dimensional preons
We prove the existence of 3/4-BPS preons in four- and five-dimensional gauged
supergravities by explicitly constructing them as smooth quotients of the AdS_4
and AdS_5 maximally supersymmetric backgrounds, respectively. This result
illustrates how the spacetime topology resurrects a fraction of supersymmetry
previously ruled out by the local analysis of the Killing spinor equations.Comment: 10 pages (a minor imprecision has been corrected
Invariant Killing spinors in 11D and type II supergravities
We present all isotropy groups and associated groups, up to discrete
identifications of the component connected to the identity, of spinors of
eleven-dimensional and type II supergravities. The groups are products
of a Spin group and an R-symmetry group of a suitable lower dimensional
supergravity theory. Using the case of SU(4)-invariant spinors as a paradigm,
we demonstrate that the groups, and so the R-symmetry groups of
lower-dimensional supergravity theories arising from compactifications, have
disconnected components. These lead to discrete symmetry groups reminiscent of
R-parity. We examine the role of disconnected components of the groups
in the choice of Killing spinor representatives and in the context of
compactifications.Comment: 22 pages, typos correcte
The holonomy of IIB supercovariant connection
We show that the holonomy of the supercovariant connection of IIB
supergravity is contained in SL(32, \bR). We also find that the holonomy
reduces to a subgroup of SL(32-N)\st (\oplus^N \bR^{32-N}) for IIB
supergravity backgrounds with Killing spinors. We give the necessary and
sufficient conditions for a IIB background to admit Killing spinors. A IIB
supersymmetric probe configuration can involve up to 31 linearly independent
planar branes and preserves one supersymmetry.Comment: 8 pages, latex. v2: Minor correction
Penrose limits of Lie Branes and a Nappi--Witten braneworld
Departing from the observation that the Penrose limit of AdS_3 x S^3 is a
group contraction in the sense of Inonu and Wigner, we explore the relation
between the symmetric D-branes of AdS_3 x S^3 and those of its Penrose limit, a
six-dimensional symmetric plane wave analogous to the four-dimensional
Nappi--Witten spacetime. Both backgrounds are Lie groups admitting bi-invariant
lorentzian metrics and symmetric D-branes wrap their (twisted) conjugacy
classes. We determine the (twisted and untwisted) symmetric D-branes in the
plane wave background and we prove the existence of a space-filling D5-brane
and, separately, of a foliation by D3-branes with the geometry of the
Nappi--Witten spacetime which can be understood as the Penrose limit of the
AdS_2 x S^2 D3-brane in AdS_3 x S^3. Parenthetically we also derive a simple
criterion for a symmetric plane wave to be isometric to a lorentzian Lie group.
In particular we observe that the maximally supersymmetric plane wave in IIB
string theory is isometric to a lorentzian Lie group, whereas the one in
M-theory is not.Comment: 21 pages (v2: references added
On the maximal superalgebras of supersymmetric backgrounds
In this note we give a precise definition of the notion of a maximal
superalgebra of certain types of supersymmetric supergravity backgrounds,
including the Freund-Rubin backgrounds, and propose a geometric construction
extending the well-known construction of its Killing superalgebra. We determine
the structure of maximal Lie superalgebras and show that there is a finite
number of isomorphism classes, all related via contractions from an
orthosymplectic Lie superalgebra. We use the structure theory to show that
maximally supersymmetric waves do not possess such a maximal superalgebra, but
that the maximally supersymmetric Freund-Rubin backgrounds do. We perform the
explicit geometric construction of the maximal superalgebra of AdS_4 x S^7 and
find that is isomorphic to osp(1|32). We propose an algebraic construction of
the maximal superalgebra of any background asymptotic to AdS_4 x S^7 and we
test this proposal by computing the maximal superalgebra of the M2-brane in its
two maximally supersymmetric limits, finding agreement.Comment: 17 page
Parallelisable Heterotic Backgrounds
We classify the simply-connected supersymmetric parallelisable backgrounds of
heterotic supergravity. They are all given by parallelised Lie groups admitting
a bi-invariant lorentzian metric. We find examples preserving 4, 8, 10, 12, 14
and 16 of the 16 supersymmetries.Comment: 17 pages, AMSLaTe
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