592 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
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
Towards Mirror Symmetry as Duality for Two-Dimensional Abelian Gauge Theories
Superconformal sigma models with Calabi--Yau target spaces described as
complete intersection subvarieties in toric varieties can be obtained as the
low-energy limit of certain abelian gauge theories in two dimensions. We
formulate mirror symmetry for this class of Calabi--Yau spaces as a duality in
the abelian gauge theory, giving the explicit mapping relating the two
Lagrangians. The duality relates inequivalent theories which lead to isomorphic
theories in the low-energy limit. This formulation suggests that mirror
symmetry could be derived using abelian duality. The application of duality in
this context is complicated by the presence of nontrivial dynamics and the
absence of a global symmetry. We propose a way to overcome these obstacles,
leading to a more symmetric Lagrangian. The argument, however, fails to produce
a derivation of the conjecture.Comment: 14 pages, latex, no figure
More on Superstrings in AdS(3) x N
We study superstring theories on AdS(3) x N backgrounds yielding N=2,3,4
extended superconformal symmetries in the dual boundary CFT. In each case the
necessary constraints on the internal worldsheet theory N are found.Comment: JHEP style, 22 pages; v2: new references and a couple of sentences on
N=1 are adde
Beyond the Singularity of the 2-D Charged Black Hole
Two dimensional charged black holes in string theory can be obtained as exact
(SL(2,R)xU(1))/U(1) quotient CFTs. The geometry of the quotient is induced from
that of the group, and in particular includes regions beyond the black hole
singularities. Moreover, wavefunctions in such black holes are obtained from
gauge invariant vertex operators in the SL(2,R) CFT, hence their behavior
beyond the singularity is determined. When the black hole is charged we find
that the wavefunctions are smooth at the singularities. Unlike the uncharged
case, scattering waves prepared beyond the singularity are not fully reflected;
part of the wave is transmitted through the singularity. Hence, the physics
outside the horizon of a charged black hole is sensitive to conditions set
behind the past singularity.Comment: 19 pages, 5 figures; v2: refs added, minor typos corrected; v3:
references on the infinite blue shift at the inner horizon and minor
corrections adde
Free field realization of superstring theory on AdS3
The Coulomb gas representation of expectation values in SU(2) conformal field
theory developed by Dotsenko is extended to the SL(2,R) WZW model and applied
to bosonic string theory on AdS3 and to Type II superstrings on AdS3 x N. The
spectral flow symmetry is included in the free field realization of vertex
operators creating superstring states of both Ramond and Neveu-Schwarz sectors.
Conjugate representations for these operators are constructed and a background
charge prescription is designed to compute correlation functions. Two and three
point functions of bosonic and fermionic string states in arbitrary winding
sectors are calculated. Scattering amplitudes that violate winding number
conservation are also discussed.Comment: 40 pages, typos corrected, references added, minor changes in
presentation and details completed in the calculation of the R sector 2-point
function. Version to appear in JHE
Duality in cosmological perturbation theory
Cosmological perturbation equations derived from low-energy effective actions
are shown to be invariant under a duality transformation reminiscent of
electric-magnetic, strong-weak coupling, S-duality. A manifestly
duality-invariant approximation for perturbations far outside the horizon is
introduced, and it is argued to be useful even during a high curvature epoch.
Duality manifests itself through a remnant symmetry acting on the classical
moduli of cosmological models, and implying lower bounds on the number and
energy density of produced particles.Comment: 14 pages, LATEX, no figure
Worldsheet correlators in AdS(3)/CFT(2)
The AdS_3/CFT_2 correspondence is checked beyond the supergravity
approximation by comparing correlation functions. To this end we calculate 2-
and 3-point functions on the sphere of certain chiral primary operators for
strings on AdS_3 x S^3 x T^4. These results are then compared with the
corresponding amplitudes in the dual 2-dimensional conformal field theory. In
the limit of small string coupling, where the sphere diagrams dominate the
string perturbation series, beautiful agreement is found.Comment: 23 page
Space-time filling branes in non critical (super) string theories
We consider solutions of (super) gravities associated to non-critical (super)
string theories in arbitrary space-time dimension D=p+3, that describe
generically non extremal black p-branes charged under NSNS or RR gauge fields,
embedded in some non critical vacuum. In the case of vacuum (uncharged)
backgrounds, we solve completely the problem obtaining all the possible
solutions, that consist of the (p+1)-dimensional Minkowski space times a linear
dilaton times a S^1, and a three parameter family of solutions that include
(p+1)-dimensional Minkowski space times the cigar, and its T-dual
(p+1)-dimensional Minkowski space times the trumpet. For NSNS charged
solutions, we also solve in closed form the problem, obtaining several families
of solutions, that include in particular the fundamental non-critical string
solution embedded in the cigar vacuum, recently found in hep-th/0604202, a
solution that we interpret as a fundamental non-critical string embedded in the
linear dilaton vacuum, and a two-parameter family of regular curvature
solutions asymptotic to AdS_{1,2}\times S^1. In the case of RR charged
Dp-branes solutions, an ansatz allows us to find a non conformal, constant
curvature, asymptotically AdS_{1,p+1} space, T-dual to AdS_{1,p+2}, together
with a two-parameter family of solutions that includes the non conformal, AdS
black hole like solution associated with the earlier space. The solutions
obtained by T-duality are Einstein spaces consisting of a two-parameter family
of conformal, constant dilaton solutions, that include, in particular, the AdS
black hole of hep-th/0403254. We speculate about the possible applications of
some of them in the framework of the gauge-gravity correspondence.Comment: 34 pages, 10 figures, to be published by Nuclear Physics
Surveying Pseudomoduli: the Good, the Bad and the Incalculable
We classify possible types of pseudomoduli which arise when supersymmetry is
dynamically broken in infrared-free low-energy theories. We show that, even if
the pseudomoduli potential is generated only at higher loops, there is a regime
where the potential can be simply determined from a combination of one-loop
running data. In this regime, we compute whether the potential for the various
types of pseudomoduli is safe, has a dangerous runaway to the UV cutoff of the
low-energy theory, or is incalculable. Our results are applicable to building
new models of supersymmetry breaking. We apply the results to survey large
classes of models.Comment: 34 page
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