103 research outputs found
Superconformal hypermultiplets
We present theories of N=2 hypermultiplets in four spacetime dimensions that are invariant under rigid or local superconformal symmetries. The target spaces of theories with rigid superconformal invariance are (4n)-dimensional {\it special} hyper-K\"ahler manifolds. Such manifolds can be described as cones over tri-Sasakian metrics and are locally the product of a flat four-dimensional space and a quaternionic manifold. The latter manifolds appear in the coupling of hypermultiplets to N=2 supergravity. We employ local sections of an Sp bundle in the formulation of the Lagrangian and transformation rules, thus allowing for arbitrary coordinatizations of the hyper-K\"ahler and quaternionic manifolds
Multiscale modelling of masonry structures using domain decomposition techniques
This paper describes the application of a domain decomposition technique for multiscale modelling of fracture behaviour in masonry. The use of multiple domains allows for a difference in employed mesh sizes for the macro- and mesoscale. For domains which play a crucial role in the failure process, we apply a mesoscale level meshing, while less critical components can be modelled by a less computationally expensive macroscale mesh. The crack behaviour is modelled by using the GFEM method, while the joint degradation is described using a plasticity based cohesive zone model, with a smooth yield surface. For the purpose of domain decomposition, we propose the use of a FETI method
Time-dependent mesoscopic modelling of masonry using embedded weak discontinuities
In this contribution, a rate-dependent mesoscopic masonry model is presented in which the mortar joints are incorporated by embedded weak discontinuities based on partitions of unity. Within the discontinuities, both an isotropic damage and a Perzyna viscoplastic model are used to describe joint degradation. The elastic domain of the joint behaviour is bounded by a modified Drucker-Prager yield function. The performance of the developed masonry model is demonstrated by the simulation of a three-point bending test and a shear wall test
Superconformal Hypermultiplets
We present theories of N=2 hypermultiplets in four spacetime dimensions that are invariant under rigid or local superconformal symmetries. The target spaces of theories with rigid superconformal invariance are (4n)-dimensional {\it special} hyper-Kähler manifolds. Such manifolds can be described as cones over tri-Sasakian metrics and are locally the product of a flat four-dimensional space and a quaternionic manifold. The latter manifolds appear in the coupling of hypermultiplets to N=2 supergravity. We employ local sections of an Sp bundle in the formulation of the Lagrangian and transformation rules, thus allowing for arbitrary coordinatizations of the hyper-Kähler and quaternionic manifolds
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
D-instantons and twistors: some exact results
We present some results on instanton corrections to the hypermultiplet moduli
space in Calabi-Yau compactifications of Type II string theories. Previously,
using twistor methods, only a class of D-instantons (D2-instantons wrapping
A-cycles) was incorporated exactly and the rest was treated only linearly. We
go beyond the linear approximation and give a set of holomorphic functions
which, through a known procedure, capture the effect of D-instantons at all
orders. Moreover, we show that for a sector where all instanton charges have
vanishing symplectic invariant scalar product, the hypermultiplet metric can be
computed explicitly.Comment: 32 pages, 3 figures, uses JHEP3.cls; some changes in section 3.3.3;
corrected formula for the contact potentia
Hypermultiplets and Topological Strings
The c-map relates classical hypermultiplet moduli spaces in compactifications
of type II strings on a Calabi-Yau threefold to vector multiplet moduli spaces
via a further compactification on a circle. We give an off-shell description of
the c-map in N=2 superspace. The superspace Lagrangian for the hypermultiplets
is a single function directly related to the prepotential of special geometry,
and can therefore be computed using topological string theory. Similarly, a
class of higher derivative terms for hypermultiplets can be computed from the
higher genus topological string amplitudes. Our results provide a framework for
studying quantum corrections to the hypermultiplet moduli space, as well as for
understanding the black hole wave-function as a function of the hypermultiplet
moduli.Comment: 21 pages, references adde
N=2 supergravity in five dimensions revisited
We construct matter-coupled N=2 supergravity in five dimensions, using the
superconformal approach. For the matter sector we take an arbitrary number of
vector-, tensor- and hyper-multiplets. By allowing off-diagonal vector-tensor
couplings we find more general results than currently known in the literature.
Our results provide the appropriate starting point for a systematic search for
BPS solutions, and for applications of M-theory compactifications on Calabi-Yau
manifolds with fluxes.Comment: 35 pages; v.2: A sign changed in a bilinear fermion term in (5.7
Instantons in the Double-Tensor Multiplet
The double-tensor multiplet naturally appears in type IIB superstring
compactifications on Calabi-Yau threefolds, and is dual to the universal
hypermultiplet. We revisit the calculation of instanton corrections to the
low-energy effective action, in the supergravity approximation. We derive a
Bogomolny'i bound for the double-tensor multiplet and find new instanton
solutions saturating the bound. They are characterized by the topological
charges and the asymptotic values of the scalar fields in the double-tensor
multiplet.Comment: 17 pages, LaTeX2e with amsmath.sty; v2: minor change
Generalized gaugings and the field-antifield formalism
We discuss the algebra of general gauge theories that are described by the
embedding tensor formalism. We compare the gauge transformations dependent and
independent of an invariant action, and argue that the generic transformations
lead to an infinitely reducible algebra. We connect the embedding tensor
formalism to the field-antifield (or Batalin-Vilkovisky) formalism, which is
the most general formulation known for general gauge theories and their
quantization. The structure equations of the embedding tensor formalism are
included in the master equation of the field-antifield formalism.Comment: 42 pages; v2: some clarifications and 1 reference added; version to
be published in JHE
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