241 research outputs found
Three-dimensional black holes from deformed anti-de Sitter
We present new exact three-dimensional black-string backgrounds, which
contain both NS--NS and electromagnetic fields, and generalize the BTZ black
holes and the black string studied by Horne and Horowitz. They are obtained as
deformations of the Sl(2,R) WZW model. Black holes resulting from purely
continuous deformations possess true curvature singularities. When discrete
identifications are introduced, extra chronological singularities appear, which
under certain circumstances turn out to be naked. The backgrounds at hand
appear in the moduli space of the Sl(2,R) WZW model. Hence, they provide exact
string backgrounds and allow for a more algebraical CFT description. This makes
possible the determination of the spectrum of primaries.Comment: JHEP style, 33 pages, 1 figur
Non-Abelian coset string backgrounds from asymptotic and initial data
We describe hierarchies of exact string backgrounds obtained as non-Abelian
cosets of orthogonal groups and having a space--time realization in terms of
gauged WZW models. For each member in these hierarchies, the target-space
backgrounds are generated by the ``boundary'' backgrounds of the next member.
We explicitly demonstrate that this property holds to all orders in .
It is a consequence of the existence of an integrable marginal operator build
on, generically, non-Abelian parafermion bilinears. These are dressed with the
dilaton supported by the extra radial dimension, whose asymptotic value defines
the boundary. Depending on the hierarchy, this boundary can be time-like or
space-like with, in the latter case, potential cosmological applications.Comment: 26 page
AdS2xS2 as an exact heterotic string background
An exact heterotic string theory on an AdS2xS2 background supported by an
electromagnetic flux is found as a marginal deformation of an SL(2,R)xSU(2) WZW
model. Based on a talk given at NATO Advanced Study Institute and EC Summer
School on String Theory: from Gauge Interactions to Cosmology, Cargese,
Corsica, France, 7 Jun - 19 Jun 2004.Comment: 5 page
Non-Critical String Duals of N=1 Quiver Theories
We construct N=1 non-critical strings in four dimensions dual to strongly
coupled N=1 quiver gauge theories in the Coulomb phase, generalizing the string
duals of Argyres-Douglas points in N=2 gauge theories. They are the first
examples of superstrings vacua with an exact worldsheet description dual to
chiral N=1 theories. We identify the dual of the non-critical superstring using
a brane setup describing the field theory in the classical limit. We analyze
the spectrum of chiral operators in the strongly coupled regime and show how
worldsheet instanton effects give non-perturbative information about the gauge
theory. We also consider aspects of D-branes relevant for the holographic
duality.Comment: JHEP style; 40 pages, 3 figures; v2: minor corrections, refs added,
version to appear in JHE
Heterotic strings on homogeneous spaces
We construct heterotic string backgrounds corresponding to families of
homogeneous spaces as exact conformal field theories. They contain left cosets
of compact groups by their maximal tori supported by NS-NS 2-forms and gauge
field fluxes. We give the general formalism and modular-invariant partition
functions, then we consider some examples such as SU(2)/U(1) ~ S^2 (already
described in a previous paper) and the SU(3)/U(1)^2 flag space. As an
application we construct new supersymmetric string vacua with magnetic fluxes
and a linear dilaton.Comment: JHEP style; 47 pages, one figur
ZZ-Branes of N=2 Super-Liouville Theory
We study conformal boundary conditions and corresponding one-point functions
of the N=2 super-Liouville theory using both conformal and modular bootstrap
methods. We have found both continuous (`FZZT-branes') and discrete
(`ZZ-branes') boundary conditions. In particular, we identify two different
types of the discrete ZZ-brane solutions, which are associated with degenerate
fields of the N=2 super-Liouville theory.Comment: 26 page
D-branes in Lorentzian AdS(3)
We study the exact construction of D-branes in Lorentzian AdS(3). We start by
defining a family of conformal field theories that gives a natural Euclidean
version of the SL(2,R) CFT and does not correspond to H(3)+, the analytic
continuation of AdS(3). We argue that one can recuperate the exact CFT results
of Lorentzian AdS(3), upon an analytic continuation in the moduli space of
these conformal field theories. Then we construct exact boundary states for
various symmetric and symmetry-breaking D-branes in AdS(3).Comment: JHEP style;21 pages, no figures; v2:some corrections, comments and
references adde
Tree-Level Stability Without Spacetime Fermions: Novel Examples in String Theory
Is perturbative stability intimately tied with the existence of spacetime
fermions in string theory in more than two dimensions? Type 0'B string theory
in ten-dimensional flat space is a rare example of a non-tachyonic,
non-supersymmetric string theory with a purely bosonic closed string spectrum.
However, all known type 0' constructions exhibit massless NSNS tadpoles
signaling the fact that we are not expanding around a true vacuum of the
theory. In this note, we are searching for perturbatively stable examples of
type 0' string theory without massless tadpoles in backgrounds with a spatially
varying dilaton. We present two examples with this property in non-critical
string theories that exhibit four- and six-dimensional Poincare invariance. We
discuss the D-branes that can be embedded in this context and the type of gauge
theories that can be constructed in this manner. We also comment on the
embedding of these non-critical models in critical string theories and their
holographic (Little String Theory) interpretation and propose a general
conjecture for the role of asymptotic supersymmetry in perturbative string
theory.Comment: harvmac, 29 pages; v2 minor changes, version to appear in JHE
D-branes at multicritical points
The moduli space of c=1 conformal field theories in two dimensions has a
multicritical point, where a circle theory is equivalent to an orbifold theory.
We analyse all the conformal branes in both descriptions of this theory, and
find convincing evidence that the full brane spectrum coincides. This shows
that the equivalence of the two descriptions at this multicritical point
extends to the boundary sector. We also perform the analogous analysis for one
of the multicritical points of the N=1 superconformal field theories at c=3/2.
Again the brane spectra are identical for both descriptions, however the
identification is more subtle.Comment: 32 pages, 2 figure
Orientifolds in N=2 Liouville Theory and its Mirror
We consider unoriented strings in the supersymmetric SL(2,R)/U(1) coset,
which describes the two-dimensional Euclidean black hole, and its mirror dual
N=2 Liouville theory. We analyze the orientifolds of these theories from
several complementary points of view: the parity symmetries of the worldsheet
actions, descent from known AdS_3 parities, and the modular bootstrap method
(in some cases we can also check our results against known constraints coming
from the conformal bootstrap method). Our analysis extends previous work on
orientifolds in Liouville theory, the AdS_3 and SU(2) WZW models and minimal
models. Compared to these cases, we find that the orientifolds of the two
dimensional Euclidean black hole exhibit new intriguing features. Our results
are relevant for the study of orientifolds in the neighborhood of NS5-branes
and for the engineering of four-dimensional chiral gauge theories and gauge
theories with SO and Sp gauge groups with suitable configurations of D-branes
and orientifolds. As an illustration, we discuss an example related to a
configuration of D4-branes and O4-planes in the presence of two parallel
fivebranes.Comment: 47 pages, 2 figures; v2 typos fixed, refs added, improved discussion
of Hanany-Witten setup
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