586 research outputs found
N=2 structures in all string theories
The BRST cohomology of any topological conformal field theory admits the
structure of a Batalin--Vilkovisky algebra, and string theories are no
exception. Let us say that two topological conformal field theories are
``cohomologically equivalent'' if their BRST cohomologies are isomorphic as
Batalin--Vilkovisky algebras. What we show in this paper is that any string
theory (regardless of the matter background) is cohomologically equivalent to
some twisted N=2 superconformal field theory. We discuss three string theories
in detail: the bosonic string, the NSR string and the W_3 string. In each case
the way the cohomological equivalence is constructed can be understood as
coupling the topological conformal field theory to topological gravity. These
results lend further supporting evidence to the conjecture that _any_
topological conformal field theory is cohomologically equivalent to some
topologically twisted N=2 superconformal field theory. We end the paper with
some comments on different notions of equivalence for topological conformal
field theories and this leads to an improved conjecture.Comment: 23 pages (12 physical pages), .dvi.uu (+ some hyperlinks
Deformations of M-theory Killing superalgebras
We classify the Lie superalgebra deformations of the Killing superalgebras of
some M-theory backgrounds. We show that the Killing superalgebras of the
Minkowski, Freund--Rubin and M5-brane backgrounds are rigid, whereas the ones
for the M-wave, the Kaluza--Klein monopole and the M2-brane admit deformations,
which we give explicitly.Comment: 20 pages (v3: a number of signs and a couple of factors have changed
without affecting the result. v4: yet more sign changes, but results remain
unchanged. v5: this is becoming absurd... but the signs ought to be correct
now! v6: no more sign changes, but section 5.2 on the MKK monopole has been
partially rewritten and some relevant references have been added.
Metric Lie n-algebras and double extensions
We prove a structure theorem for Lie n-algebras possessing an invariant inner
product. We define the notion of a double extension of a metric Lie n-algebra
by another Lie n-algebra and prove that all metric Lie n-algebras are obtained
from the simple and one-dimensional ones by iterating the operations of
orthogonal direct sum and double extension.Comment: 10 page
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
The Classical Limit of W-Algebras
We define and compute explicitly the classical limit of the realizations of
appearing as hamiltonian structures of generalized KdV hierarchies. The
classical limit is obtained by taking the commutative limit of the ring of
pseudodifferential operators. These algebras---denoted ---have free field
realizations in which the generators are given by the elementary symmetric
polynomials in the free fields. We compute the algebras explicitly and we show
that they are all reductions of a new algebra , which is proposed
as the universal classical -algebra for the series. As a deformation
of this algebra we also obtain , the classical limit of
.Comment: (14 pages
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