103 research outputs found
Spectral Flow in AdS(3)/CFT(2)
We study the spectral flowed sectors of the H3 WZW model in the context of
the holographic duality between type IIB string theory in AdS(3)x S^3 x T^4
with NSNS flux and the symmetric product orbifold of T^4. We construct
explicitly the physical vertex operators in the flowed sectors that belong to
short representations of the superalgebra, thus completing the bulk-to-boundary
dictionary for 1/2 BPS states. We perform a partial calculation of the string
three-point functions of these operators. A complete calculation would require
the three-point couplings of non-extremal flowed operators in the H3 WZW model,
which are at present unavailable. In the unflowed sector, perfect agreement has
recently been found between the bulk and boundary three-point functions of 1/2
BPS operators. Assuming that this agreement persists in the flowed sectors, we
determine certain unknown three-point couplings in the H3 WZW model in terms of
three-point couplings of affine descendants in the SU(2) WZW model.Comment: 50 pages, 2 figure
The BRST quantization and the no-ghost theorem for AdS_3
In our previous papers, we prove the no-ghost theorem without light-cone
directions (hep-th/0005002, hep-th/0303051). We point out that our results are
valid for more general backgrounds. In particular, we prove the no-ghost
theorem for AdS_3 in the context of the BRST quantization (with the standard
restriction on the spin). We compare our BRST proof with the OCQ proof and
establish the BRST-OCQ equivalence for AdS_3. The key in both approaches lies
in the certain structure of the matter Hilbert space as a product of two Verma
modules. We also present the no-ghost theorem in the most general form.Comment: 22 pages, JHEP and AMS-LaTeX; v2 & 3: minor improvement
S-matrix for magnons in the D1-D5 system
We show that integrability and symmetries of the near horizon geometry of the
D1-D5 system determine the S-matrix for the scattering of magnons with
polarizations in AdS3 S3 completely up to a phase. Using
semi-classical methods we evaluate the phase to the leading and to the one-loop
approximation in the strong coupling expansion. We then show that the phase
obeys the unitarity constraint implied by the crossing relations to the
one-loop order. We also verify that the dispersion relation obeyed by these
magnons is one-loop exact at strong coupling which is consistent with their BPS
nature.Comment: 40 pages, Latex, Role of Virasoro constraints clarified, version
matches with published versio
BRST Quantization of String Theory in AdS(3)
We study the BRST quantization of bosonic and NSR strings propagating in
AdS(3) x N backgrounds. The no-ghost theorem is proved using the
Frenkel-Garland-Zuckerman method. Regular and spectrally-flowed representations
of affine SL(2,R) appear on an equal footing. Possible generalizations to
related curved backgrounds are discussed.Comment: JHEP style, 23 pages; v2:minor changes and references added; v3:
typos corrected, version to appear in JHEP; v4: one reference adde
A Spin Chain for the Symmetric Product CFT_2
We consider "gauge invariant" operators in Sym^N T^4, the symmetric product
orbifold of N copies of the 2d supersymmetric sigma model with T^4 target. We
discuss a spin chain representation for single-cycle operators and study their
two point functions at large N. We perform systematic calculations at the
orbifold point ("tree level"), where non-trivial mixing is already present, and
some sample calculations to first order in the blow-up mode of the orbifold
("one loop").Comment: 52 pages, 10 figure
Entanglement entropy of two dimensional systems and holography
In this note a new method for computing the entanglement entropy of a CFT
holographically is explored. It consists of finding a bulk background with a
boundary metric that has the conical singularities needed to compute the
entanglement entropy in the usual QFT definition. An explicit calculation is
presented for d=2.Comment: 20 pages, 1 figure: v2 typos fixed, references and comments adde
Extremal Correlators and Hurwitz Numbers in Symmetric Product Orbifolds
We study correlation functions of single-cycle chiral operators in the
symmetric product orbifold of N supersymmetric four-tori. Correlators of twist
operators are evaluated on covering surfaces, generally of different genera,
where fields are single-valued. We compute some simple four-point functions and
study how the sum over inequivalent branched covering maps splits under OPEs.
We then discuss extremal n-point correlators, i.e. correlators of n-1 chiral
and one anti-chiral operators. They obey simple recursion relations involving
numbers obtained from counting branched covering maps with particular
properties. In most cases we are able to solve explicitly the recursion
relations. Remarkably, extremal correlators turn out to be equal to Hurwitz
numbers.Comment: 36 pages, 3 figures, v2: minor improvement
Diagrams for Symmetric Product Orbifolds
We develop a diagrammatic language for symmetric product orbifolds of
two-dimensional conformal field theories. Correlation functions of twist
operators are written as sums of diagrams: each diagram corresponds to a
branched covering map from a surface where the fields are single-valued to the
base sphere where twist operators are inserted. This diagrammatic language
facilitates the study of the large N limit and makes more transparent the
analogy between symmetric product orbifolds and free non-abelian gauge
theories. We give a general algorithm to calculate the leading large N
contribution to four-point correlators of twist fields.Comment: 43 pages, 19 figures, v2: references adde
The diagonal cosets of the Heisenberg group
In this paper we study the diagonal cosets of the non-compact H4 WZW model.
Generalising earlier work by Antoniadis and Obers, we provide an exact
world-sheet description for several families of non-maximally symmetric
gravitational plane waves with background NS fluxes. We show that the
sigma-models that correspond to an asymmetric action of the gauge group
smoothly interpolate between singular and non-singular plane waves. We also
analyse the representations of the coset chiral algebra and derive the spectrum
of all the models.Comment: 42 pages, v2: more explicit expressions for the background fields in
section 3.2.2, reference [49] added, some typos correcte
From Matrices to Strings and Back
We discuss an explicit construction of a string dual for the Gaussian matrix
model. Starting from the matrix model and employing Strebel differential
techniques we deduce hints about the structure of the dual string. Next,
following these hints a worldheet theory is constructed. The correlators in
this string theory are assumed to localize on a finite set of points in the
moduli space of Riemann surfaces. To each such point one associates a Feynman
diagram contributing to the correlator in the dual matrix model, and thus
recasts the worldsheet expression as a sum over Feynman diagrams.Comment: 27 pages, 3 figure
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