1,092 research outputs found
Domain Walls on the Brane
We show that all branes admit worldvolume domain wall solutions. We find one
class of solutions for which the tension of the brane changes discontinuously
along the domain wall. These solutions are not supersymmetric. We argue that
there is another class of domain wall solutions which is supersymmetric. A
particular case concerns supersymmetric domain wall solutions on IIB D-5- and
NS-5-branes.Comment: 18 pages, Tex, uses phyzz
Q7-branes and their coupling to IIB supergravity
We show how, by making use of a new basis of the IIB supergravity
axion-dilaton coset, SL(2,R)/SO(2), 7-branes that belong to different conjugacy
classes of the duality group SL(2,R) naturally couple to IIB supergravity with
appropriate source terms characterized by an SL(2,R) charge matrix Q. The
conjugacy classes are determined by the value of the determinant of Q. The
(p,q) 7-branes are the branes in the conjugacy class detQ = 0. The 7-branes in
the conjugacy class detQ > 0 are labelled by three numbers (p,q,r) which
parameterize the matrix Q and will be called Q7-branes. We construct the full
bosonic Wess--Zumino term for the Q7-branes. In order to realize a gauge
invariant coupling of the Q7-brane to the gauge fields of IIB supergravity it
is necessary to introduce an SL(2,R) doublet of two distinct Born--Infeld
fields on the Q7-brane world-volume.Comment: 31 pages, Latex fil
Kappa-symmetric SL(2,R) covariant D-brane actions
A superspace formulation of IIB supergravity which includes the field
strengths of the duals of the usual physical one, three and five-form field
strengths as well as the eleven-form field strength is given. The
superembedding formalism is used to construct kappa-symmetric SL(2,R) covariant
D-brane actions in an arbitrary supergravity background.Comment: 20 pages. Minor clarification in text. References adde
Duality of Type II 7-branes and 8-branes
We present a version of ten-dimensional IIA supergravity containing a 9-form
potential for which the field equations are equivalent to those of the
standard, massless, IIA theory for vanishing 10-form field strength, ,
and to those of the `massive' IIA theory for non-vanishing . We present
a multi 8-brane solution of these equations that generalizes the 8-brane of
Polchinski and Witten. We show that this solution is T-dual to a new multi
7-brane solution of compactified IIB supergravity, and that the latter is
T-dual to the IIA 6-brane. When combined with the U-duality of the
type IIB superstring, the T-duality between type II 7-branes and 8-branes
implies a quantization of the cosmological constant of type IIA superstring
theory. These results are made possible by the construction of a new {\it
massive} N=2 D=9 supergravity theory. We also discuss the 11-dimensional
interpretation of these type II p-branes.Comment: Includes corrections to last section that will appear in the version
to be published in Nuclear Physics B. 36 pp. Phyzz
IIA/IIB Supergravity and Ten-forms
We perform a careful investigation of which p-form fields can be introduced
consistently with the supersymmetry algebra of IIA and/or IIB ten-dimensional
supergravity. In particular the ten-forms, also known as "top-forms", require a
careful analysis since in this case, as we will show, closure of the
supersymmetry algebra at the linear level does not imply closure at the
non-linear level. Consequently, some of the (IIA and IIB) ten-form potentials
introduced in earlier work of some of us are discarded. At the same time we
show that new ten-form potentials, consistent with the full non-linear
supersymmetry algebra can be introduced. We give a superspace explanation of
our work. All of our results are precisely in line with the predictions of the
E(11) algebra.Comment: 17 page
Higher Derivative Extension of 6D Chiral Gauged Supergravity
Six-dimensional (1,0) supersymmetric gauged Einstein-Maxwell supergravity is
extended by the inclusion of a supersymmetric Riemann tensor squared invariant.
Both the original model as well as the Riemann tensor squared invariant are
formulated off-shell and consequently the total action is off-shell invariant
without modification of the supersymmetry transformation rules. In this
formulation, superconformal techniques, in which the dilaton Weyl multiplet
plays a crucial role, are used. It is found that the gauging of the U(1)
R-symmetry in the presence of the higher-order derivative terms does not modify
the positive exponential in the dilaton potential. Moreover, the supersymmetric
Minkowski(4) x S^2 compactification of the original model, without the
higher-order derivatives, is remarkably left intact. It is shown that the model
also admits non-supersymmetric vacuum solutions that are direct product spaces
involving de Sitter spacetimes and negative curvature internal spaces.Comment: 32 pages; typos corrected, footnote in conclusions section adde
The identification of conformal hypercomplex and quaternionic manifolds
We review the map between hypercomplex manifolds that admit a closed
homothetic Killing vector (i.e. `conformal hypercomplex' manifolds) and
quaternionic manifolds of 1 dimension less. This map is related to a method for
constructing supergravity theories using superconformal techniques. An explicit
relation between the structure of these manifolds is presented, including
curvatures and symmetries. An important role is played by `\xi
transformations', relating connections on quaternionic manifolds, and a new
type `\hat\xi transformations' relating complex structures on conformal
hypercomplex manifolds. In this map, the subclass of conformal hyper-Kaehler
manifolds is mapped to quaternionic-Kaehler manifolds.Comment: 22 pages, 2 figures, Contribution to the proceedings volume for the
Conference "Symmetry in Geometry and Physics" in honour of Dmitri
Alekseevsky, September 200
Spectrum of Higher Derivative 6D Chiral Supergravity
Gauged off-shell Maxwell-Einstein supergravity in six dimensions with N=(1,0)
supersymmetry has a higher derivative extension afforded by a supersymmetrized
Riemann squared term. This theory admits a supersymmetric Minkowski x S^2
compactification with a U(1) monopole of unit charge on S^2. We determine the
full spectrum of the theory on this background. We also determine the spectrum
on a non-supersymmetric version of this compactification in which the monopole
charge is different from unity, and we find the peculiar feature that there are
massless gravitini in a representation of the S^2 isometry group determined by
the monopole charge.Comment: typos correcte
Classical resolution of singularities in dilaton cosmologies
For models of dilaton-gravity with a possible exponential potential, such as
the tensor-scalar sector of IIA supergravity, we show how cosmological
solutions correspond to trajectories in a 2D Milne space (parametrized by the
dilaton and the scale factor). Cosmological singularities correspond to points
at which a trajectory meets the Milne horizon, but the trajectories can be
smoothly continued through the horizon to an instanton solution of the
Euclidean theory. We find some exact cosmology/instanton solutions that lift to
black holes in one higher dimension. For one such solution, the singularities
of a big crunch to big bang transition mediated by an instanton phase lift to
the black hole and cosmological horizons of de Sitter Schwarzschild spacetimes.Comment: 24 pages, 2 figure
Domain walls and instantons in N=1, d=4 supergravity
We study the supersymmetric sources of (multi-) domain-wall and (multi-)
instanton solutions of generic N=1, d=4 supergravities, that is: the
worldvolume effective actions for said supersymmetric topological defects. The
domain-wall solutions naturally couple to the two 3-forms recently found as
part of the N=1, d=4 tensor hierarchy (i.e. they have two charges in general)
and their tension is the absolute value of the superpotential section L. The
introduction of sources (we study sources with finite and vanishing thickness)
is equivalent to the introduction of local coupling constants and results in
dramatic changes of the solutions. Our results call for a democratic
reformulation of N=1,d=4 supergravity in which coupling constants are,
off-shell, scalar fields. The effective actions for the instantons are always
proportional to the coordinate orthogonal to the twist-free embedding of the
null-geodesic (in the Wick-rotated scalar manifold) describing the instanton.
We show their supersymmetry and find the associated supersymmetric (multi-)
instanton solutions.Comment: 34 pages, 4 figures, references adde
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