377 research outputs found
Non-simply-laced Lie algebras via F theory strings
In order to describe the appearance in F theory of the non--simply--laced Lie
algebras, we use the representation of symmetry enhancements by means of string
junctions. After an introduction to the techniques used to describe symmetry
enhancement, that is algebraic geometry, BPS states analysis and string
junctions, we concentrate on the latter. We give an explicit description of the
folding of D_{2n} to B_n of the folding of E_6 to F_4 and that of D_4 to G_2 in
terms of junctions and Jordan strings. We also discuss the case of C_n, but we
are unable in this case to provide a string interpretation.Comment: 24 pages, 3 figure
Non-Abelian (p,q) Strings in the Warped Deformed Conifold
We calculate the tension of -strings in the warped deformed conifold
using the non-Abelian DBI action. In the large flux limit, we find exact
agreement with the recent expression obtained by Firouzjahi, Leblond and
Henry-Tye up to and including order terms if is also taken to be
large. Furthermore using the finite prescription for the symmetrised trace
operation we anticipate the most general expression for the tension valid for
any . We find that even in this instance, corrections to the tension
scale as which is not consistent with simple Casimir scaling.Comment: 18 pages, Latex, 1 figure; Added a discussion of the case when the
warp factor parameter and typos correcte
Fermion localization on degenerate and critical branes
In this work we analyze the localization of fermions on degenerate and
critical Bloch branes. This is done directly on physical coordinates, in
constrast to some works that has been using conformal coordinates. We find the
range of coupling constants of the interaction of fermions with the scalar
fields that allow us to have normalizable fermion zero-mode localized on the
brane on both, critical and degenerate Bloch branes. In the case of critical
branes our results agree with those found in [Class. Quantum Grav. \textbf{27}
(2010) 185001]. The results on fermion localization on degenerate Bloch branes
are new. We also propose a coupling of fermions to the scalar fields which
leads to localization of massless fermion on both sides of a double-brane.Comment: 16 pages, 6 figure
Higgs Phenomenon for 4-D Gravity in Anti de Sitter Space
We show that standard Einstein gravity coupled to a free conformal field
theory (CFT) in Anti de Sitter space can undergo a Higgs phenomenon whereby the
graviton acquires a nonzero mass (and three extra polarizations). We show that
the essential ingredients of this mechanism are the discreteness of the energy
spectrum in AdS space, and unusual boundary conditions on the elementary fields
of the CFT. These boundary conditions can be interpreted as implying the
existence of a 3-d defect CFT living at the boundary of the AdS space. Our
free-field computation sheds light on the essential, model-independent features
of AdS that give rise to massive gravity.Comment: 17 page
Superconformal Gauge Theories and Non-Critical Superstrings
We consider effective actions for six-dimensional non-critical superstrings.
We show that the addition of units of R-R flux and of space-time
filling D5-branes produces solutions with curvature
comparable to the string scale. These solutions have the right structure to be
dual to supersymmetric SU(N) gauge theories with flavors. We
further suggest bounds on the mass-squared of tachyonic fields in this
background that should restrict the theory to the conformal window.Comment: 16 pages, 1 figure v4: Minor change
Local models for intersecting brane worlds
We describe the construction of configurations of D6-branes wrapped on
compact 3-cycles intersecting at points in non-compact Calabi-Yau threefolds.
Such constructions provide local models of intersecting brane worlds, and
describe sectors of four-dimensional gauge theories with chiral fermions. We
present several classes of non-compact manifolds with compact 3-cycles
intersecting at points, and discuss the rules required for model building with
wrapped D6-branes. The rules to build 3-cycles are simple, and allow easy
computation of chiral spectra, RR tadpoles and the amount of preserved
supersymmetry. We present several explicit examples of these constructions,
some of which have Standard Model like gauge group and three quark-lepton
generations. In some cases, mirror symmetry relates the models to other
constructions used in phenomenological D-brane model building, like D-branes at
singularities. Some simple N=1 supersymmetric configurations may lead to
relatively tractable G_2 manifolds upon lift to M-theory, which would be
non-compact but nevertheless yield four-dimensional chiral gauge field
theories.Comment: 52 pages, latex, 24 enclosed eps figures; v2. typo correcte
Glueball Scattering Amplitudes from Holography
Using techniques developed in a previous paper three-point functions in field
theories described by holographic renormalization group flows are computed. We
consider a system of one active scalar and one inert scalar coupled to gravity.
For the GPPZ flow, their dual operators create states that are interpreted as
glueballs of the N=1 SYM theory, which lies at the infrared end of the
renormalization group flow. The scattering amplitudes for three-glueball
processes are calculated providing precise predictions for glueball decays in
N=1 SYM theory. Numerical results for low-lying glueballs are included.Comment: 34 pages v2: comments on local terms and references added, v3:
version published in JHE
On the Existence of Meta-stable Vacua in Klebanov-Strassler
We solve for the complete space of linearized deformations of the
Klebanov-Strassler background consistent with the symmetries preserved by a
stack of anti-D3 branes smeared on the of the deformed conifold. We find
that the only solution whose UV physics is consistent with that of a
perturbation produced by anti-D3 branes must have a singularity in the
infrared, coming from NS and RR three-form field strengths whose energy density
diverges. If this singularity is admissible, our solution describes the
backreaction of the anti-D3 branes, and is thus likely to be dual to the
conjectured metastable vacuum in the Klebanov-Strassler field theory. If this
singularity is not admissible, then our analysis strongly suggests that anti-D3
branes do not give rise to metastable Klebanov-Strassler vacua, which would
have dramatic consequences for some string theory constructions of de Sitter
space. Key to this result is a simple, universal form for the force on a probe
D3-brane in our ansatz.Comment: 35 pages, LaTeX. v2: further details provided regarding the IR
singularity and the discussion modified accordingly. typos corrected, refs
adde
Generalized Flux Vacua
We consider type II string theory compactified on a symmetric T^6/Z_2
orientifold. We study a general class of discrete deformations of the resulting
four-dimensional supergravity theory, including gaugings arising from geometric
and "nongeometric'' fluxes, as well as the usual R-R and NS-NS fluxes. Solving
the equations of motion associated with the resulting N = 1 superpotential, we
find parametrically controllable infinite families of supersymmetric vacua with
all moduli stabilized. We also describe some aspects of the distribution of
generic solutions to the SUSY equations of motion for this model, and note in
particular the existence of an apparently infinite number of solutions in a
finite range of the parameter space of the four-dimensional effective theory.Comment: 30 pages, 4 .eps figures; v2, reference adde
On effective action of string theory flux compactifications
We discuss four dimensional effective actions of string theory flux
compactifications. These effective actions describe four dimensional gravity
coupled to overall Kahler modulus of the compactification manifold. We
demonstrate the agreement between ten dimensional equations of motion of
supergravity with localized branes, and equations of motion derived from the
effective action. The agreement is lost however if one evaluates the full
effective action on the equations of motion for a subset of the supergravity
modes, provided these modes depend on-shell on the Kahler modulus.Comment: 25 pages; v2: refs adde
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