1,006 research outputs found

### Unitarity of supersymmetric SL(2,R)/U(1) and no-ghost theorem for fermionic strings in AdS(3) x N

The unitarity of the NS supersymmetric coset SL(2,R)/U(1) is studied for the
discrete representations. The results are applied to the proof of the no-ghost
theorem for fermionic strings in AdS(3) x N in the NS sector. A no-ghost
theorem is proved for states in flowed discrete representations.Comment: LaTeX in JHEP style, 16 pages, typos correcte

### 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

### Aspects of Space-Time Dualities

Duality groups of Abelian gauge theories on four manifolds and their
reduction to two dimensions are considered. The duality groups include elements
that relate different space-times in addition to relating different
gauge-coupling matrices. We interpret (some of) such dualities as the
geometrical symmetries of compactified theories in higher dimensions. In
particular, we consider compactifications of a (self-dual) 2-form in 6-D, and
compactifications of a self-dual 4-form in 10-D. Relations with a self-dual
superstring in 6-D and with the type IIB superstring are discussed.Comment: 10 pages, plain Latex. Minor misprint correcte

### 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

### 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

### A non-reductive N=4 superconformal algebra

A new N=4 superconformal algebra (SCA) is presented. Its internal affine Lie
algebra is based on the seven-dimensional Lie algebra su(2)\oplus g, where g
should be identified with a four-dimensional non-reductive Lie algebra. Thus,
it is the first known example of what we choose to call a non-reductive SCA. It
contains a total of 16 generators and is obtained by a non-trivial
In\"on\"u-Wigner contraction of the well-known large N=4 SCA. The recently
discovered asymmetric N=4 SCA is a subalgebra of this new SCA. Finally, the
possible affine extensions of the non-reductive Lie algebra g are classified.
The two-form governing the extension appearing in the SCA differs from the
ordinary Cartan-Killing form.Comment: 10 pages, LaTeX, version to be publishe

### Type 0 Strings in a 2-d Black Hole

We study some aspects of type 0 strings propagating in the two dimensional
black hole geometry, corresponding to the exact SL(2)/U(1) SCFT background.Comment: 33 pages, harvmac. v2: minor clarification adde

### A Change of Variables to the Dual and Factorization of Composite Anomalous Jacobians

Changes of variables giving the dual model are constructed explicitly for
sigma-models without isotropy. In particular, the jacobian is calculated to
give the known results. The global aspects of the abelian case as well as some
of those of the cases where the isometry group is simply connected are
considered.
Considering the anomalous case, we infer by a consistency argument that the
`multiplicative anomaly' should be replaceable by adequate rules for
factorization of composite jacobians. These rules are then generalized in a
simple way for composite jacobians defined in spaces of different types.
Implimentation of these rules then gives specific formulas for the anomally for
semisimple algebras and also for solvable ones.Comment: 15 pages, no figures, Latex file, A treatment of the global aspects
of the abelian and of semisimple duality groups are added. General formulas
for the mixed anomaly are derive

### 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 $g_s\to
0$. 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 $AdS_3$ 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

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