300 research outputs found
Meson spectroscopy from holomorphic probes on the warped deformed conifold
We study D7 brane probes holomorphically embedded in the Klebanov-Strassler
model. Analyzing the -symmetry condition for D7 branes wrapping a
4-cycle of a deformed conifold we find configurations that do not break N=1
supersymmetry of the background. We compute the fluctuations of the probe
around one of these configurations and obtain the spectrum of vector and scalar
flavored mesons in the dual gauge theory. The spectrum is discrete and exhibits
a mass gap.Comment: 22 pages, JHEP style, 2 figure
A note on dark energy induced by D-brane motion
In this note we study the possibility of obtaining dark energy solution in a
D-brane scenario in a warped background that includes brane-position dependent
corrections for the non-perturbative superpotential. The volume modulus is
stabilized at instantaneous minima of the potential. Though the model can
account for the existence of dark energy within present observational bound -
fine-tuning of the model parameters becomes unavoidable. Moreover, the model
does not posses a tracker solution.Comment: 5 pages, 4 figure
On Isolated Conformal Fixed Points and Noncritical String Theory
We search for the gravity description of unidentified field theories at their
conformal fixed points by studying the low energy effective action of six
dimensional noncritical string theory. We find constant dilaton solutions by
solving both the equations of motion and BPS equations. Our solutions include a
free parameter provided by a stack of uncharged space filling branes. We find
several AdS_p\times S^q solutions with constant radii for AdS_p and S^q. The
curvature of the solutions are of the order of the string scale.Comment: 17 pages, Latex fil
Scalar Spectrum from a Dynamical Gravity/Gauge model
We show that a Dynamical AdS/QCD model is able to reproduce the linear Regge
trajectories for the light-flavor sector of mesons with high spin and also for
the scalar and pseudoscalar ones. In addition the model has confinement by the
Wilson loop criteria and a mass gap. We also calculate the decay amplitude of
scalars into two pion in good agreement to the available experimental data.Comment: Presented in the 4th International Workshop on Astronomy and
Relativistic Astrophysic
On the pp-wave limit and the BMN structure of new Sasaki-Einstein spaces
We construct the pp-wave string associated with the Penrose limit of
and families of Sasaki-Einstein geometries. We identify
in the dual quiver gauge theories the chiral and the non-chiral operators that
correspond to the ground state and the first excited states. We present an
explicit identification in a prototype model of .Comment: 21 pages, JHEP format, 5 figures, acknowledgement correcte
Cascading Quivers from Decaying D-branes
We use an argument analogous to that of Kachru, Pearson and Verlinde to argue
that cascades in L^{a,b,c} quiver gauge theories always preserve the form of
the quiver, and that all gauge groups drop at each step by the number M of
fractional branes. In particular, we demonstrate that an NS5-brane that sweeps
out the S^3 of the base of L^{a,b,c} destroys M D3-branes.Comment: 11 pages, 1 figure; v2: references adde
Holographic technicolor models and their S-parameter
We study the Peskin-Takeuchi S-parameter of holographic technicolor models.
We present the recipe for computing the parameter in a generalized holographic
setup. We then apply it to several holographic models that include: (a) the
Sakai-Sugimoto model and (b) its non-compactified cousin, (c) a non-critical
analog of (a) based on near extremal AdS_6 background, (d) the KMMW model which
is similar to model (a) but with D6 and anti-D6 flavor branes replacing the D8
and anti-D8 branes, (e) a model based on D5 branes compactified on two S^1s
with D7 and anti-7 probe branes and (f) the conifold model with the same probe
branes as in (e). The models are gravity duals of gauge theories with U(N_{TC})
gauge theory and with a breakdown of a flavor symmetry U(N_{TF})xU(N_{TF}) to
U_V(N_{TF}). The models (a), (c),(d) and (e) are duals of a confining gauge
theories whereas (b) and (f) associate with non confining models.
The S-parameter was found to be S=sN_{TC} where s is given by
0.017\lambda_{TC}, 0.016\lambda_{TC}, 0.095, 0.50 and 0.043 for the
(a),(b),(c),(d), (f) models respectively and for model (e) s is divergent.
These results are valid in the large N_{TC} and large \lambda_{TC} limit. We
further derive the dependence of the S-parameter on the "string endpoint" mass
of the techniquarks for the various models. We compute the masses of the low
lying vector technimesons.Comment: 37 pages, 2 figures V2: 2 coerrections in sectionss 4 and 5,
reference adde
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