2,161 research outputs found
More Anomalies from Fractional Branes
In this note we show how the anomalies of both pure and matter coupled N=1,2
supersymmetric gauge theories describing the low energy dynamics of fractional
branes on orbifolds can be derived from supergravity.Comment: 11 pages, latex; v2: minor typos fixe
Interaction of Discrete States in Two-Dimensional String Theory
We study the couplings of discrete states that appear in the string theory
embedded in two dimensions, and show that they are given by the structure
constants of the group of area preserving diffeomorphisms. We propose an
effective action for these states, which is itself invariant under this
infinite-dimensional group.Comment: 12 page
A Gravity Dual of the Chiral Anomaly
We study effects associated with the chiral anomaly for a cascading
gauge theory using gauge/gravity duality. In the gravity
dual the anomaly is a classical feature of the supergravity solution, and the
breaking of the U(1) R-symmetry down to proceeds via the Higgs
mechanism.Comment: 15 pages, derivation of vector mass corrected, main conclusions
unchanged, a sign convention changed in section
Gauge/gravity correspondence in accelerating universe
We discuss time-dependent backgrounds of type IIB supergravity realizing
gravitation duals of gauge theories formulated in de Sitter space-time as a
tool of embedding de Sitter in a supergravity. We show that only the
gravitational duals to non-conformal gauge theories are sensitive to a specific
value of a Hubble parameter. We consider two nontrivial solutions of this type:
a gravity dual to six-dimensional (1,1) little string theory, and to a
four-dimensional cascading SU(N+M)xSU(N) supersymmetric gauge theory (related
to fractional D3-branes on a singular conifold according to Klebanov et al), in
accelerating universe. In both cases we argue that the IR singularity of the
geometry is regulated by the expansion of the gauge theory background
space-time.Comment: 13 pages, harvmac, v2: reference added, v3: D3,NS5 discussion
improved, PRD versio
Perturbative Search for Fixed Lines in Large N Gauge Theories
The logarithmic running of marginal double-trace operators is a general
feature of 4-d field theories containing scalar fields in the adjoint or
bifundamental representation. Such operators provide leading contributions in
the large N limit; therefore, the leading terms in their beta functions must
vanish for a theory to be large N conformal. We calculate the one-loop beta
functions in orbifolds of the N=4 SYM theory by a discrete subgroup Gamma of
the SU(4) R-symmetry, which are dual to string theory on AdS_5 x S^5/Gamma. We
present a general strategy for determining whether there is a fixed line
passing through the origin of the coupling constant space. Then we study in
detail some classes of non-supersymmetric orbifold theories, and emphasize the
importance of decoupling the U(1) factors. Among our examples, which include
orbifolds acting freely on the S^5, we do not find any large N
non-supersymmetric theories with fixed lines passing through the origin.
Connection of these results with closed string tachyon condensation in AdS_5 x
S^5/Gamma is discussed.Comment: 31 pages, 4 figures, latex v2: Clarifications and reference adde
Scattering of Open and Closed Strings in 1+1 Dimensions
The ground ring structure of 1+1 dimensional string theory leads to an
infinite set of non linear recursion relations among the `bulk' scattering
amplitudes of open and closed tachyons on the disk, which fix them uniquely.
The relations are generated by the action of the ring on the tachyon modules;
associativity of this action determines all structure constants. This algebraic
structure may allow one to relate the continuum picture to a matrix model.Comment: 16 page
QCD and String Theory
This talk begins with some history and basic facts about string theory and
its connections with strong interactions. Comparisons of stacks of Dirichlet
branes with curved backgrounds produced by them are used to motivate the
AdS/CFT correspondence between superconformal gauge theory and string theory on
a product of Anti-de Sitter space and a compact manifold. The ensuing duality
between semi-classical spinning strings and long gauge theory operators is
briefly reviewed. Strongly coupled thermal SYM theory is explored via a black
hole in 5-dimensional AdS space, which leads to explicit results for its
entropy and shear viscosity. A conjectured universal lower bound on the
viscosity to entropy density ratio, and its possible relation to recent results
from RHIC, are discussed. Finally, some available results on string duals of
confining gauge theories are briefly reviewed.Comment: 12 pages, prepared for the Proceedings of the 2005 Lepton-Photon
Symposium; v2: minor revisions, references added, the version to appear in
the proceeding
Absorption by Threebranes and the AdS/CFT Correspondence
In the first part of this talk I discuss two somewhat different supergravity
approaches to calculating correlation functions in strongly coupled Yang-Mills
theory. The older approach relates two-point functions to cross-sections for
absorption of certain incident quanta by threebranes. In this approach the
normalization of operators corresponding to the incident particles is fixed
unambiguously by the D3-brane DBI action. By calculating absorption
cross-sections of all partial waves of the dilaton we find corresponding
two-point functions at strong `t Hooft coupling and show that they are
identical to the weak coupling results. The newer approach to correlation
functions relates them to boundary conditions in AdS space. Using this method
we show that for a certain range of negative mass-squared there are two
possible operator dimensions corresponding to a given scalar field in AdS, and
indicate how to calculate correlation functions for either of these choices. In
the second part of the talk I discuss an example of AdS/CFT duality which
arises in the context of type 0 string theory. The CFT on N coincident electric
and magnetic D3-branes is argued to be stable for sufficiently weak `t Hooft
coupling. It is suggested that its transition to instability at a critical
coupling is related to singularity of planar diagrams.Comment: 14 pages, LaTeX; Talk at Strings '99, Potsdam, German
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