625 research outputs found
D-branes in group manifolds
In this paper we re-examine the geometric interpretation of gluing conditions
in WZW models and the possible D-brane configurations that they give rise to.
We show how the boundary conditions are encoded in the gluing conditions
imposed on the chiral currents. We analyse two special classes of gluing
conditions: the first, which preserves the affine symmetry of the bulk theory,
describes D-branes whose worldvolumes are given by `twisted' conjugacy classes;
the second class describes configurations which include subgroups and cosets.Comment: 23 page
Lie-Poisson groups and the Miura transformation
We point out that the recent proof of the Kupershmidt-Wilson theorem by Cheng
and Mas-Ramos is underpinned by the Lie-Poisson property of the second
Gel'fand-Dickey bracket. The supersymmetric Kupershmidt-Wilson theorem is also
proved along these same lines. Finally we comment on the possible repercussions
in the problem of the coproduct for W-algebras.Comment: .dvi file, uses AMSFonts 2.1+, 10 pages (5 physical pages in
landscape mode), no figure
D-brane charge, flux quantisation and relative (co)homology
We reconsider the problem of U(1) flux and D0-charge for D-branes in the WZW
model and investigate the relationship between the different definitions that
have been proposed recently. We identify the D0-charge as a particular
reduction of a class in the relative cohomology of the group modulo the
D-submanifold. We investigate under which conditions this class is equivalent
to the first Chern class of a line bundle on the D-submanifold and we find that
in general there is an obstruction given by the cohomology class of the NS
3-form. Therefore we conclude that for topologically nontrivial B-fields, there
is strictly speaking no U(1) gauge field on the D-submanifold. Nevertheless the
ambiguity in the flux is not detected by the D0-charge. This has a natural
interpretation in terms of gerbes.Comment: 16 pages, 3 figures (v2: cosmetic changes and definition of relative
de Rham complex
New Supersymmetrizations of the Generalized KdV Hierarchies
Recently we investigated a new supersymmetrization procedure for the KdV
hierarchy inspired in some recent work on supersymmetric matrix models. We
extend this procedure here for the generalized KdV hierarchies. The resulting
supersymmetric hierarchies are generically nonlocal, except for the case of
Boussinesque which we treat in detail. The resulting supersymmetric hierarchy
is integrable and bihamiltonian and contains the Boussinesque hierarchy as a
subhierarchy. In a particular realization, we extend it by defining
supersymmetric odd flows. We end with some comments on a slight modification of
this supersymmetrization which yields local equations for any generalized KdV
hierarchy.Comment: 10 pages, uuencoded compressed tar'd .dvi file, Bonn-HE-93-1
On the structure of symmetric self-dual Lie algebras
A finite-dimensional Lie algebra is called (symmetric) self-dual, if it possesses an invariant nondegenerate (symmetric) bilinear form. Symmetric self-dual Lie algebras have been studied by Medina and Revoy, who have proven a very useful theorem about their structure. In this paper we prove a refinement of their theorem which has wide applicability in Conformal Field Theory, where symmetric self-dual Lie algebras start to play an important role due to the fact that they are precisely the Lie algebras which admit a Sugawara construction. We also prove a few corollaries which are important in Conformal Field Theory. (This paper provides mathematical details of results used, but only sketched, in the companion paper hep-th/9506151.
D-branes with Lorentzian signature in the Nappi-Witten model
Lorentzian signature D-branes of all dimensions for the Nappi-Witten string
are constructed. This is done by rewriting the gluing condition for
the model chiral currents on the brane as a well posed first order differential
problem and by solving it for Lie algebra isometries other than Lie algebra
automorphisms. By construction, these D-branes are not twined conjugacy
classes. Metrically degenerate D-branes are also obtained.Comment: 22 page
Gauging the Wess-Zumino term of a sigma model with boundary
We investigate the gauging of the Wess-Zumino term of a sigma model with
boundary. We derive a set of obstructions to gauging and we interpret them as
the conditions for the Wess-Zumino term to extend to a closed form in a
suitable equivariant relative de Rham complex. We illustrate this with the
two-dimensional sigma model and we show that the new obstructions due to the
boundary can be interpreted in terms of Courant algebroids. We specialise to
the case of the Wess-Zumino-Witten model, where it is proved that there always
exist suitable boundary conditions which allow gauging any subgroup which can
be gauged in the absence of a boundary. We illustrate this with two natural
classes of gaugings: (twisted) diagonal subgroups with boundary conditions
given by (twisted) conjugacy classes, and chiral isotropic subgroups with
boundary conditions given by cosets.Comment: 18 pages (minor changes in response to referee report
More D-branes in the Nappi-Witten background
We re-examine the problem of determining the possible D-branes in the
Nappi-Witten background. In addition to the known branes, we find that there
are also D-instantons, flat euclidean D-strings and curved D-membranes
admitting parallel spinors, all of which can be interpreted as (twisted)
conjugacy classes in the Nappi-Witten group.Comment: 21 pages, 4 figures. (A small correction in Section 2.4
- âŠ