1,935 research outputs found
Q-instantons
We construct the half-supersymmetric instanton solutions that are
electric-magnetically dual to the recently discussed half-supersymmetric
Q7-branes. We call these instantons `Q-instantons'. Whereas the D-instanton is
most conveniently described using the RR axion \chi and the dilaton \phi, the
Q-instanton is most conveniently described using a different set of fields
\chi' and T, where \chi' is an axionic scalar. The real part of the Q-instanton
on-shell action is a function of T and the imaginary part is linear in \chi'.
Discrete shifts of the axion \chi' correspond to PSL(2,Z) transformations that
are of finite order. These are e.g. pure S-duality transformations relating
weak and strongly coupled regimes. We argue that near each orbifold point of
the quantum axion-dilaton moduli space PSL(2,Z)\PSL(2,R)/SO(2) the higher order
R^4 terms in the string effective action contain contributions from an infinite
sum of single multiply-charged instantons with the Q-instantons corresponding
to the orbifold points \tau=i,\rho where \tau is the complex axion-dilaton
field.Comment: 29 pages, 1 figur
Defect Branes
We discuss some general properties of "defect branes", i.e. branes of
co-dimension two, in (toroidally compactified) IIA/IIB string theory. In
particular, we give a full classification of the supersymmetric defect branes
in dimensions 2 < D < 11 as well as their higher-dimensionalstring and M-theory
origin as branes and a set of "generalized" Kaluza-Klein monopoles. We point
out a relation between the generalized Kaluza-Klein monopole solutions and a
particular type of mixed-symmetry tensors. These mixed-symmetry tensors can be
defined at the linearized level as duals of the supergravity potentials that
describe propagating degrees of freedom. It is noted that the number of
supersymmetric defect branes is always twice the number of corresponding
central charges in the supersymmetry algebra.Comment: Latex2e paper, 28 pages, no figures. Footnote adde
Brane orbits
We complete the classification of half-supersymmetric branes in toroidally
compactified IIA/IIB string theory in terms of representations of the T-duality
group. As a by-product we derive a last wrapping rule for the space-filling
branes. We find examples of T-duality representations of branes in lower
dimensions, suggested by supergravity, of which none of the component branes
follow from the reduction of any brane in ten-dimensional IIA/IIB string
theory. We discuss the constraints on the charges of half-supersymmetric
branes, determining the corresponding T-duality and U-duality orbits.Comment: 34 pages, 3 figure
Seven-branes and Supersymmetry
We re-investigate the construction of half-supersymmetric 7-brane solutions
of IIB supergravity. Our method is based on the requirement of having globally
well-defined Killing spinors and the inclusion of SL(2,Z)-invariant source
terms. In addition to the well-known solutions going back to Greene, Shapere,
Vafa and Yau we find new supersymmetric configurations, containing objects
whose monodromies are not related to the monodromy of a D7-brane by an SL(2,Z)
transformation.Comment: 31 pages, 3 figure
SL(2,R)-invariant IIB Brane Actions
We give a universal SL(2,R)-invariant expression for all IIB p-brane actions
with p=-1,1,3,5,7,9. The Wess-Zumino terms in the brane actions are determined
by requiring (i) target space gauge invariance and (ii) the presence of a
single Born-Infeld vector. We find that for p=7 (p=9) brane actions with these
properties only exist for orbits that contain the standard D7-brane (D9-brane).
We comment about the actions for the other orbits.Comment: 15 pages, additional references and remarks in subsection on
3-branes, accepted for publication in JHE
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
Non-propagating degrees of freedom in supergravity and very extended G_2
Recently a correspondence between non-propagating degrees of freedom in
maximal supergravity and the very extended algebra E_11 has been found. We
perform a similar analysis for a supergravity theory with eight supercharges
and very extended G_2. In particular, in the context of d=5 minimal
supergravity, we study whether supersymmetry can be realised on higher-rank
tensors with no propagating degrees of freedom. We find that in this case the
very extended algebra fails to capture these possibilities.Comment: 12 pages, 1 figure. v2: transformation properties of higher-rank
tensors under SU(2) R-symmetry analysed and refs added. v3: improved
discussion, published versio
Wrapping rules (in) string theory
In this paper we show that the number of all 1/2-BPS branes in string theory
compactified on a torus can be derived by universal wrapping rules whose
formulation we present. These rules even apply to branes in less than ten
dimensions whose ten-dimensional origin is an exotic brane. In that case the
wrapping rules contain an additional combinatorial factor that is related to
the highest dimension in which the ten-dimensional exotic brane, after
compactification, can be realized as a standard brane. We show that the
wrapping rules also apply to cases with less supersymmetry. As a specific
example, we discuss the compactification of IIA/IIB string theory on
.Comment: 21 page
BPS Open Strings and A-D-E-singularities in F-theory on K3
We improve on a recently constructed graphical representation of the
supergravity 7-brane solution and apply this refined representation to re-study
the open string description of the A-D-E-singularities in F-theory on K3. A
noteworthy feature of the graphical representation is that it provides the
complete global branch cut structure of the 7-brane solution which plays an
important role in our analysis. We first identify those groups of branes which
when made to coincide lead to the A-D-E-gauge groups. We next show that there
is always a sufficient number of open BPS strings to account for all the
generators of the gauge group. However, as we will show, there is in general no
one-to-one relation between BPS strings and gauge group generators.
For the D_{n+4}- and E-singularities, in order to relate BPS strings with
gauge group generators, we make an SU(n+4), respectively SU(5) subgroup of the
D_{n+4}- and E-gauge groups manifest. We find that only for the D-series (and
for the standard A-series) this is sufficient to identify, in a one-to-one
manner, which BPS strings correspond to which gauge group generators.Comment: 37 pages, 15 figure
Three-Dimensional Extended Bargmann Supergravity
We show that three-dimensional General Relativity, augmented with two vector
fields, allows for a non-relativistic limit, different from the standard limit
leading to Newtonian gravity, that results into a well-defined action which is
of the Chern-Simons type. We show that this three-dimensional `Extended
Bargmann Gravity', after coupling to matter, leads to equations of motion
allowing a wider class of background geometries than the ones that one
encounters in Newtonian gravity. We give the supersymmetric generalization of
these results and point out an important application in the context of
calculating partition functions of non-relativistic field theories using
localization techniques.Comment: 6 pages, v2: typo's corrected, reference updated, accepted for
publication in Phys. Rev. Let
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