181 research outputs found
Comments on Double Scaled Little String Theory
We study little string theory in a weak coupling limit defined in \gk.Comment: 22 pages, harvmac; minor change
Little String Theory in a Double Scaling Limit
A double scaling limit can be defined in string theory on a Calabi-Yau (CY)
manifold by approaching a point in moduli space where the CY space develops an
isolated singularity and at the same time taking the string coupling to zero,
while keeping a particular combination of the two parameters fixed. This leads
to a decoupled theory without gravity which has a weak coupling expansion, and
can be studied using a holographically dual non-critical superstring
description. The usual ``Little String Theory'' corresponds to the strong
coupling limit of this theory. We use holography to compute two and three point
functions in weakly coupled double scaled little string theory, and study the
spectrum of the theory in various dimensions. We find a discrete spectrum of
masses which exhibits Hagedorn growth.Comment: 23 pages, harvmac; minor change
Holography for Non-Critical Superstrings
We argue that a class of ``non-critical superstring'' vacua is
holographically related to the (non-gravitational) theory obtained by studying
string theory on a singular Calabi-Yau manifold in the decoupling limit . In two dimensions, adding fundamental strings at the singularity of the CY
manifold leads to conformal field theories dual to a recently constructed class
of vacua. In four dimensions, special cases of the construction
correspond to the theory on an NS5-brane wrapped around a Riemann surface.Comment: 29 pages, harvmac; minor changes, references adde
Coset Character Identities in Superstring Compactifications
We apply the coset character identities (generalization of Jacobi's abstruse
identity) to compact and noncompact Gepner models. In the both cases, we prove
that the partition function actually vanishes due to the spacetime
supersymmetry. In the case of the compact models and discrete parts of the
noncompact models, the partition function includes the expected vanishing
factor. But the character identities used to the continuous part of the
noncompact models suggest that these models have twice as many supersymmetry as
expected. This fact is an evidence for the conjecture that the holographically
dual of the string theory on an actually singular Calabi-Yau manifold is a
super CONFORMAL field theory. The extra SUSY charges are interpreted as the
superconformal S generators.Comment: 23 pages, LaTeX, no figure. v2:corrected typos, added detailed
calculations, added references. v3:corrected typo
On Black Fundamental Strings
We study aspects of four dimensional black holes with two electric charges,
corresponding to fundamental strings with generic momentum and winding on an
internal circle. The perturbative \alpha' correction to such black holes and
their gravitational thermodynamics is obtained.Comment: 17 pages, v2: published versio
Fundamental Strings and Black Holes
We propose a black hole thermodynamic description of highly excited charged
and uncharged perturbative string states in 3+1 dimensional type II and 4+1
dimensional heterotic string theory. We also discuss the generalization to
extremal and non-extremal black holes carrying magnetic charges.Comment: 25 pages, harvmac; V2: Added reference
Curvature formula for the space of 2-d conformal field theories
We derive a formula for the curvature tensor of the natural Riemannian metric
on the space of two-dimensional conformal field theories and also a formula for
the curvature tensor of the space of boundary conformal field theories.Comment: 36 pages, 1 figure; v2 references adde
Non-Supersymmetric Deformations of Non-Critical Superstrings
We study certain supersymmetry breaking deformations of linear dilaton
backgrounds in different dimensions. In some cases, the deformed theory has
bulk closed strings tachyons. In other cases there are no bulk tachyons, but
there are localized tachyons. The real time condensation of these localized
tachyons is described by an exactly solvable worldsheet CFT. We also find some
stable, non-supersymmetric backgrounds.Comment: 33 pages, references adde
Comments on geometric and universal open string tachyons near fivebranes
In a recent paper (hep-th/0703157), Sen studied unstable D-branes in
NS5-branes backgrounds and argued that in the strong curvature regime the
universal open string tachyon (on D-branes of the wrong dimensionality) and the
geometric tachyon (on D-branes that are BPS in flat space but not in this
background) may become equivalent. We study in this note an example of a
non-BPS suspended D-brane vs. a BPS D-brane at equal distance between two
fivebranes. We use boundary worldsheet CFT methods to show that these two
unstable branes are identical.Comment: 8 pages, 1 figure; ver. 2 to appear in JHEP: one comment, refs and
appendices adde
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