1,577 research outputs found
All null supersymmetric backgrounds of N=2, D=4 gauged supergravity coupled to abelian vector multiplets
The lightlike supersymmetric solutions of N=2, D=4 gauged supergravity
coupled to an arbitrary number of abelian vector multiplets are classified
using spinorial geometry techniques. The solutions fall into two classes,
depending on whether the Killing spinor is constant or not. In both cases, we
give explicit examples of supersymmetric backgrounds. Among these BPS
solutions, which preserve one quarter of the supersymmetry, there are
gravitational waves propagating on domain walls or on bubbles of nothing that
asymptote to AdS_4. Furthermore, we obtain the additional constraints obeyed by
half-supersymmetric vacua. These are divided into four categories, that include
bubbles of nothing which are asymptotically AdS_4, pp-waves on domain walls,
AdS_3 x R, and spacetimes conformal to AdS_3 times an interval.Comment: 55 pages, uses JHEP3.cls. v2: Minor errors corrected, small changes
in introductio
M-Horizons
We solve the Killing spinor equations and determine the near horizon
geometries of M-theory that preserve at least one supersymmetry. The M-horizon
spatial sections are 9-dimensional manifolds with a Spin(7) structure
restricted by geometric constraints which we give explicitly. We also provide
an alternative characterization of the solutions of the Killing spinor
equation, utilizing the compactness of the horizon section and the field
equations, by proving a Lichnerowicz type of theorem which implies that the
zero modes of a Dirac operator coupled to 4-form fluxes are Killing spinors. We
use this, and the maximum principle, to solve the field equations of the theory
for some special cases and present some examples.Comment: 36 pages, latex. Reference added, minor typos correcte
Three-dimensional N=8 conformal supergravity and its coupling to BLG M2-branes
This paper is concerned with the problem of coupling the N=8 superconformal
Bagger-Lambert-Gustavsson (BLG) theory to N=8 conformal supergravity in three
dimensions. We start by constructing the on-shell N=8 conformal supergravity in
three dimensions consisting of a Chern-Simons type term for each of the gauge
fields: the spin connection, the SO(8) R-symmetry gauge field and the spin 3/2
Rarita-Schwinger (gravitino) field. We then proceed to couple this theory to
the BLG theory. The final theory should have the same physical content, i.e.,
degrees of freedom, as the ordinary BLG theory. We discuss briefly the
properties of this "topologically gauged" BLG theory and why this theory may be
useful.Comment: 20 pages, v2: references and comments added, presentation in section
3.2 extended. v3: misprints and a sign error corrected, version published in
JHE
Light-cone analysis of ungauged and topologically gauged BLG theories
We consider three-dimensional maximally superconformal
Bagger-Lambert-Gustavsson (BLG) theory and its topologically gauged version
(constructed recently in arXiv:0809.4478 [hep-th]) in the light-cone gauge.
After eliminating the entire Chern-Simons gauge field, the ungauged BLG theory
looks more conventional and, apart from the order of the interaction terms,
resembles N=4 super-Yang-Mills theory in four dimensions. The light-cone
superspace version of the BLG theory is given to quadratic and quartic order
and some problems with constructing the sixth order interaction terms are
discussed. In the topologically gauged case, we analyze the field equations
related to the three Chern-Simons type terms of N=8 conformal supergravity and
discuss some of the special features of this theory and its couplings to BLG.Comment: 22 pages; v2 some typos correcte
All the supersymmetric solutions of N=1,d=5 ungauged supergravity
We classify the supersymmetric solutions of ungauged N=1 d=5 SUGRA coupled to
vector multiplets and hypermultiplets. All the solutions can be seen as
deformations of solutions with frozen hyperscalars. We show explicitly how the
5-dimensional Reissner-Nordstrom black hole is deformed when hyperscalars are
living on SO(4,1)/SO(4) are turned on, reducing its supersymmetry from 1/2 to
1/8. We also describe in the timelike and null cases the solutions that have
one extra isometry and can be reduced to N=2,d=4 solutions. Our formulae allows
the uplifting of certain N=2,d=4 black holes to N=1,d=5 black holes on KK
monopoles or to pp-waves propagating along black strings.Comment: Some typos fixed and some paragraphs improved. 44 pages, Latex 2e
file, no figures. Version to be published in JHE
A hybrid landmark Aalen-Johansen estimator for transition probabilities in partially non-Markov multi-state models
Multi-state models are increasingly being used to model complex
epidemiological and clinical outcomes over time. It is common to assume that
the models are Markov, but the assumption can often be unrealistic. The Markov
assumption is seldomly checked and violations can lead to biased estimation for
many parameters of interest. As argued by Datta and Satten (2001), the
Aalen-Johansen estimator of occupation probabilities is consistent also in the
non-Markov case. Putter and Spitoni (2018) exploit this fact to construct a
consistent estimator of state transition probabilities, the landmark
Aalen-Johansen estimator, which does not rely on the Markov assumption. A
disadvantage of landmarking is data reduction, leading to a loss of power. This
is problematic for less traveled transitions, and undesirable when such
transitions indeed exhibit Markov behaviour. Using a framework of partially
non-Markov multi-state models we suggest a hybrid landmark Aalen-Johansen
estimator for transition probabilities. The proposed estimator is a compromise
between regular Aalen-Johansen and landmark estimation, using transition
specific landmarking, and can drastically improve statistical power. The
methods are compared in a simulation study and in a real data application
modelling individual transitions between states of sick leave, disability,
education, work and unemployment. In the application, a birth cohort of 184951
Norwegian men are followed for 14 years from the year they turn 21, using data
from national registries
Systematics of M-theory spinorial geometry
We reduce the classification of all supersymmetric backgrounds in eleven
dimensions to the evaluation of the supercovariant derivative and of an
integrability condition, which contains the field equations, on six types of
spinors. We determine the expression of the supercovariant derivative on all
six types of spinors and give in each case the field equations that do not
arise as the integrability conditions of Killing spinor equations. The Killing
spinor equations of a background become a linear system for the fluxes,
geometry and spacetime derivatives of the functions that determine the spinors.
The solution of the linear system expresses the fluxes in terms of the geometry
and specifies the restrictions on the geometry of spacetime for all
supersymmetric backgrounds. We also show that the minimum number of field
equations that is needed for a supersymmetric configuration to be a solution of
eleven-dimensional supergravity can be found by solving a linear system. The
linear systems of the Killing spinor equations and their integrability
conditions are given in both a timelike and a null spinor basis. We illustrate
the construction with examples.Comment: 46 pages. v2: systematics of a null spinor basis is included in
section
Mass-Deformed BLG Theory in Light-Cone Superspace
Maximally supersymmetric mass deformation of the Bagger-Lambert-Gustavsson
(BLG) theory corresponds to a {non-central} extension of the d=3 N=8 Poincare
superalgebra (allowed in three dimensions). We obtain its light-cone superspace
formulation which has a novel feature of the dynamical supersymmetry generators
being {cubic} in the kinematical ones. The mass deformation picks a
quaternionic direction, which breaks the SO(8) R-symmetry down to SO(4)xSO(4).
The Hamiltonian of the theory is shown to be a quadratic form of the dynamical
supersymmetry transformations, to all orders in the mass parameter, M, and the
structure constants, f^{a b c d}.Comment: 23 page
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