326 research outputs found
Extensions of 2D Gravity
After reviewing some aspects of gravity in two dimensions, it is shown that
non-trivial embeddings of sl(2) in a semi-simple (super) Lie algebra give rise
to a very large class of extensions of 2D gravity. The induced action is
constructed as a gauged WZW model and an exact expression for the effective
action is given. (Talk presented at the Journees Relativistes '93, Brussels,
April, 1993).Comment: 12 pages (LaTeX, 3 eps figures), LBL-34240, UCB-PTH-93/2
On the Landau-Ginzburg Realization of Topological Gravities
We study the equivariant cohomology of a class of multi-field topological LG
models, and find that such systems carry intrinsic information about
-gravity. As a result, we can construct the gravitational chiral ring in
terms of LG polynomials. We find, in particular, that the spectrum of such
theories seems to be richer than so far expected. We also briefly discuss the
BRST operator for non-linear topological -gravity.Comment: 26p, harvmac, 4 uuencoded PostScript figure
Superstrings from Hamiltonian Reduction
In any string theory there is a hidden, twisted superconformal symmetry
algebra, part of which is made up by the BRST current and the anti-ghost. We
investigate how this algebra can be systematically constructed for strings with
supersymmetries, via quantum Hamiltonian reduction of the Lie
superalgebras . The motivation is to understand how one could
systematically construct generalized string theories from superalgebras. We
also briefly discuss the BRST algebra of the topological string, which is a
doubly twisted superconformal algebra.Comment: 32p, LaTeX, CERN-TH.7379/9
Topological Strings from WZW Models
We show that the BRST structure of the topological string is encoded in the
``small'' superconformal algebra, enabling us to obtain, in a non-trivial
way, the string theory from hamiltonian reduction of . This leads to
the important conclusion that not only ordinary string theories, but
topological strings as well, can be obtained, or even defined, by hamiltonian
reduction from WZW models. Using two different gradations, we find either the
standard minimal models coupled to topological gravity, or an embedding
of the bosonic string into the topological string. We also comment briefly on
the generalization to super Lie algebras .Comment: 14p, late
Supersymmetric non-abelian Born-Infeld revisited
We determine the non-abelian Born-Infeld action, including fermions, as it
results from the four-point tree-level open superstring scattering amplitudes
at order alpha'^2. We find that, after an appropriate field redefinition all
terms at this order can be written as a symmetrised trace. We confront this
action with the results that follow from kappa-symmetry and conclude that the
recently proposed non-abelian kappa-symmetry cannot be extended to cubic orders
in the Born-Infeld curvature.Comment: 26 pages, Late
Superspace WZW Models and Black Holes
We show how to write an off-shell action for the
supersymmetric WZW model in terms of chiral and twisted chiral
multiplets. We discuss the supersymmetry of this model and exhibit the
superconformal current algebra. Finally, we show that the off-shell
formulation makes it possible to perform a duality transformation, which leads
to a supersymmetric sigma model on a manifold with a black hole type
singularity.Comment: 12 page
A derivation of the BRST operator for non-critical W-strings:Dedicated to Professor F. Cerulus on the occasion of his 65th Birthday
We derive the recently proposed BRST charge for non-critical W strings from a lagrangian approach. The basic observation is that, despite appearances, the combination of two classical "matter" and "Toda" w3 systems leads to a closed modified gauge algebra, which is of the so-called soft type. Based on these observations, a novel way to construct critical w3 strings is given.</p
Strings from Gauged Wess-Zumino-Witten Models
We present an algebraic approach to string theory. An embedding of
in a super Lie algebra together with a grading on the Lie algebra determines a
nilpotent subalgebra of the super Lie algebra. Chirally gauging this subalgebra
in the corresponding Wess-Zumino-Witten model, breaks the affine symmetry of
the Wess-Zumino-Witten model to some extension of the superconformal
algebra. The extension is completely determined by the embedding. The
realization of the superconformal algebra is determined by the grading. For a
particular choice of grading, one obtains in this way, after twisting, the BRST
structure of a string theory. We classify all embeddings of into Lie
super algebras and give a detailed account of the branching of the adjoint
representation. This provides an exhaustive classification and characterization
of both all extended superconformal algebras and all string theories
which can be obtained in this way.Comment: 50 pages, LaTe
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