244 research outputs found
Evaluation Of Glueball Masses From Supergravity
In the framework of the conjectured duality relation between large gauge
theory and supergravity the spectra of masses in large gauge theory can be
determined by solving certain eigenvalue problems in supergravity. In this
paper we study the eigenmass problem given by Witten as a possible
approximation for masses in QCD without supersymmetry. We place a particular
emphasis on the treatment of the horizon and related boundary conditions. We
construct exact expressions for the analytic expansions of the wave functions
both at the horizon and at infinity and show that requiring smoothness at the
horizon and normalizability gives a well defined eigenvalue problem. We show
for example that there are no smooth solutions with vanishing derivative at the
horizon. The mass eigenvalues up to corresponding to smooth
normalizable wave functions are presented. We comment on the relation of our
work with the results found in a recent paper by Cs\'aki et al.,
hep-th/9806021, which addresses the same problem.Comment: 20 pages,Latex,3 figs,psfig.tex, added refs., minor change
Seiberg-Witten Transforms of Noncommutative Solitons
We evaluate the Seiberg-Witten map for solitons and instantons in
noncommutative gauge theories in various dimensions. We show that solitons
constructed using the projection operators have delta-function supports when
expressed in the commutative variables. This gives a precise identification of
the moduli of these solutions as locations of branes. On the other hand, an
instanton solution in four dimensions allows deformation away from the
projection operator construction. We evaluate the Seiberg-Witten transform of
the U(2) instanton and show that it has a finite size determined by the
noncommutative scale and by the deformation parameter \rho. For large \rho, the
profile of the D0-brane density of the instanton agrees surprisingly well with
that of the BPST instanton on commutative space.Comment: 29 pages, LaTeX; comments added, typos corrected, and a reference
added; comments added, typos correcte
Can Quantum de Sitter Space Have Finite Entropy?
If one tries to view de Sitter as a true (as opposed to a meta-stable)
vacuum, there is a tension between the finiteness of its entropy and the
infinite-dimensionality of its Hilbert space. We invetsigate the viability of
one proposal to reconcile this tension using -deformation. After defining a
differential geometry on the quantum de Sitter space, we try to constrain the
value of the deformation parameter by imposing the condition that in the
undeformed limit, we want the real form of the (inherently complex) quantum
group to reduce to the usual SO(4,1) of de Sitter. We find that this forces
to be a real number. Since it is known that quantum groups have
finite-dimensional representations only for root of unity, this suggests
that standard -deformations cannot give rise to finite dimensional Hilbert
spaces, ruling out finite entropy for q-deformed de Sitter.Comment: 10 pages, v2: references added, v3: minor corrections, abstract and
title made more in-line with the result, v4: published versio
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
Massless black holes and black rings as effective geometries of the D1-D5 system
We compute correlation functions in the AdS/CFT correspondence to study the
emergence of effective spacetime geometries describing complex underlying
microstates. The basic argument is that almost all microstates of fixed charges
lie close to certain "typical" configurations. These give a universal response
to generic probes, which is captured by an emergent geometry. The details of
the microstates can only be observed by atypical probes. We compute two point
functions in typical ground states of the Ramond sector of the D1-D5 CFT, and
compare with bulk two-point functions computed in asymptotically AdS_3
geometries. For large central charge (which leads to a good semiclassical
limit), and sufficiently small time separation, a typical Ramond ground state
of vanishing R-charge has the M=0 BTZ black hole as its effective description.
At large time separation this effective description breaks down. The CFT
correlators we compute take over, and give a response whose details depend on
the microstate. We also discuss typical states with nonzero R-charge, and argue
that the effective geometry should be a singular black ring. Our results
support the argument that a black hole geometry should be understood as an
effective coarse-grained description that accurately describes the results of
certain typical measurements, but breaks down in general.Comment: 47 pages, 4 figures. v2: references added. v3: minor corrections to
Appendix A, references adde
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Kaluza-Klein supergravity on AdS_3 x S^3
We construct a Chern-Simons type gauged N=8 supergravity in three spacetime
dimensions with gauge group SO(4) x T_\infty over the infinite dimensional
coset space SO(8,\infty)/(SO(8) x SO(\infty)), where T_\infty is an infinite
dimensional translation subgroup of SO(8,\infty). This theory describes the
effective interactions of the (infinitely many) supermultiplets contained in
the two spin-1 Kaluza-Klein towers arising in the compactification of N=(2,0)
supergravity in six dimensions on AdS_3 x S^3 with the massless supergravity
multiplet. After the elimination of the gauge fields associated with T_\infty,
one is left with a Yang Mills type gauged supergravity with gauge group SO(4),
and in the vacuum the symmetry is broken to the (super-)isometry group of AdS_3
x S^3, with infinitely many fields acquiring masses by a variant of the
Brout-Englert-Higgs effect.Comment: LaTeX2e, 24 pages; v2: references update
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