126 research outputs found
A new maximally supersymmetric background of IIB superstring theory
We present a maximally supersymmetric IIB string background. The geometry is
that of a conformally flat lorentzian symmetric space G/K with solvable G, with
a homogeneous five-form flux. We give the explicit supergravity solution,
compute the isometries, the 32 Killing spinors, and the symmetry superalgebra,
and then discuss T-duality and the relation to M-theory.Comment: 17 page
Geometry, Isometries and Gauging of (2,1) Heterotic Sigma-Models
The geometry of (2,1) supersymmetric sigma-models is reviewed and the
conditions under which they have isometry symmetries are analysed. Certain
potentials are constructed that play an important role in the gauging of such
symmetries. The gauged action is found for a special class of models.Comment: 12 pages, LaTeX, no figures. Minor changes; version to appear in
Physics Letters
Conformal topological Yang-Mills theory and de Sitter holography
A new topological conformal field theory in four Euclidean dimensions is
constructed from N=4 super Yang-Mills theory by twisting the whole of the
conformal group with the whole of the R-symmetry group, resulting in a theory
that is conformally invariant and has two conformally invariant BRST operators.
A curved space generalisation is found on any Riemannian 4-fold. This
formulation has local Weyl invariance and two Weyl-invariant BRST symmetries,
with an action and energy-momentum tensor that are BRST-exact. This theory is
expected to have a holographic dual in 5-dimensional de Sitter space.Comment: 34 pages, AMSTex, Reference adde
The Current Landscape of Pitfalls in Ontologies
A growing number of ontologies are already available thanks to development initiatives in many different
fields. In such ontology developments, developers must tackle a wide range of difficulties and handicaps,
which can result in the appearance of anomalies in the resulting ontologies. Therefore, ontology evaluation
plays a key role in ontology development projects. OOPS! is an on-line tool that automatically detects pitfalls,
considered as potential errors or problems, and thus may help ontology developers to improve their ontologies.
To gain insight in the existence of pitfalls and to assess whether there are differences among ontologies
developed by novices, a random set of already scanned ontologies, and existing well-known ones, data of 406
OWL ontologies were analysed on OOPS!’s 21 pitfalls, of which 24 ontologies were also examined manually
on the detected pitfalls. The various analyses performed show only minor differences between the three sets
of ontologies, therewith providing a general landscape of pitfalls in ontologies
Global Aspects of T-Duality, Gauged Sigma Models and T-Folds
The gauged sigma-model argument that string backgrounds related by T-dual
give equivalent quantum theories is revisited, taking careful account of global
considerations. The topological obstructions to gauging sigma-models give rise
to obstructions to T-duality, but these are milder than those for gauging: it
is possible to T-dualise a large class of sigma-models that cannot be gauged.
For backgrounds that are torus fibrations, it is expected that T-duality can be
applied fibrewise in the general case in which there are no globally-defined
Killing vector fields, so that there is no isometry symmetry that can be
gauged; the derivation of T-duality is extended to this case. The T-duality
transformations are presented in terms of globally-defined quantities. The
generalisation to non-geometric string backgrounds is discussed, the conditions
for the T-dual background to be geometric found and the topology of T-folds
analysed.Comment: Minor corrections and addition
N=2 structures on solvable Lie algebras: the c=9 classification
Let G be a finite-dimensional Lie algebra (not necessarily semisimple). It is
known that if G is self-dual (that is, if it possesses an invariant metric)
then there is a canonical N=1 superconformal algebra associated to its N=1
affinization---that is, it admits an N=1 (affine) Sugawara construction. Under
certain additional hypotheses, this N=1 structure admits an N=2 extension. If
this is the case, G is said to possess an N=2 structure. It is also known that
an N=2 structure on a self-dual Lie algebra G is equivalent to a vector space
decomposition G = G_+ \oplus G_- where G_\pm are isotropic Lie subalgebras. In
other words, N=2 structures on G are in one-to-one correspondence with Manin
triples (G,G_+,G_-). In this paper we exploit this correspondence to obtain a
classification of the c=9 N=2 structures on self-dual solvable Lie algebras. In
the process we also give some simple proofs for a variety of Lie algebraic
results concerning self-dual Lie algebras admitting symplectic or K\"ahler
structures.Comment: 49 pages in 2 columns (=25 physical pages), (uufiles-gz-9)'d .dvi
file (uses AMSFonts 2.1+). Revision: Added 1 reference, corrected typos,
added some more materia
Some Spacetimes with Higher Rank Killing-Stackel Tensors
By applying the lightlike Eisenhart lift to several known examples of
low-dimensional integrable systems admitting integrals of motion of
higher-order in momenta, we obtain four- and higher-dimensional Lorentzian
spacetimes with irreducible higher-rank Killing tensors. Such metrics, we
believe, are first examples of spacetimes admitting higher-rank Killing
tensors. Included in our examples is a four-dimensional supersymmetric pp-wave
spacetime, whose geodesic flow is superintegrable. The Killing tensors satisfy
a non-trivial Poisson-Schouten-Nijenhuis algebra. We discuss the extension to
the quantum regime
Uniqueness of M-theory PP-Wave Background with Extra Supersymmetries
We examine Killing spinor equations of the general eleven-dimensional pp-wave
backgrounds, which contain a scalar H(x^m,x^-) in the metric and a three-form
\xi(x^m,x^-) in the flux. Considering non-harmonic extra Killing spinors, we
show that if the backgrounds admit at least one extra Killing spinor in
addition to the standard 16 Killing spinors, they can be reduced to the form
with H=A_{mn}(x^-)x^mx^n and \xi(x^-) modulo coordinate transformations. We
further examine the cases in which the extra Killing spinor is characterized by
a set of Cartan matrices. The super-isometry algebras of the resulting
backgrounds are also derived.Comment: 25 pages, LaTeX2e, comments added, version to appear in PR
Properties of branes in curved spacetimes
A generic property of curved manifolds is the existence of focal points. We
show that branes located at focal points of the geometry satisfy special
properties. Examples of backgrounds to which our discussion applies are AdS_m x
S^n and plane wave backgrounds. As an example, we show that a pair of AdS_2
branes located at the north and south pole of the S^5 in AdS_5 x S^5 are half
supersymmetric and that they are dual to a two-monopole solution of N=4 SU(N)
SYM theory. Our second example involves spacelike branes in the (Lorentzian)
plane wave. We develop a modified lightcone gauge for the open string channel,
analyze in detail the cylinder diagram and establish open-closed duality. When
the branes are located at focal points of the geometry the amplitude acquires
most of the characteristics of flat space amplitudes. In the open string
channel the special properties are due to stringy modes that become massless.Comment: 41 pages; v2:typos corrected, ref adde
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