3,285 research outputs found
New Supergravity Backgrounds Dual to N=1 SQCD-like Theories with N_f=2N_c
We present new supergravity backgrounds generated by N_c D5-branes, wrapping
the S^2 of the resolved conifold, in the presence of N_f = 2 N_c smeared flavor
D5-branes. The smearing allows us to take their backreaction on the geometry
into account. We discuss the consistency, stability, and supersymmetry of these
types of setups. We find near horizon geometries that we expect to be
supergravity duals of SQCD-like theories with N_f= 2N_c. From these backgrounds
we numerically extract rectangular Wilson loops and beta functions of the dual
field theory for the regime where our approximations are valid.Comment: 22+24 pages, 17 figures, Figure 12 replace
Drag force in a string model dual to large-N QCD
We compute the drag force exerted on a quark and a di-quark systems in a
background dual to large-N QCD at finite temperature. We find that appears a
drag force in the former setup with flow of energy proportional to the mass of
the quark while in the latter there is no dragging as in other studies. We also
review the screening length.Comment: 15 pages, typos removed, error corrected, refs adde
The intrinsic three-dimensional shape of galactic bars
We present the first statistical study on the intrinsic three-dimensional
(3D) shape of a sample of 83 galactic bars extracted from the CALIFA survey. We
use the galaXYZ code to derive the bar intrinsic shape with a statistical
approach. The method uses only the geometric information (ellipticities and
position angles) of bars and discs obtained from a multi-component photometric
decomposition of the galaxy surface-brightness distributions. We find that bars
are predominantly prolate-triaxial ellipsoids (68%), with a small fraction of
oblate-triaxial ellipsoids (32%). The typical flattening (intrinsic C/A
semiaxis ratio) of the bars in our sample is 0.34, which matches well the
typical intrinsic flattening of stellar discs at these galaxy masses. We
demonstrate that, for prolate-triaxial bars, the intrinsic shape of bars
depends on the galaxy Hubble type and stellar mass (bars in massive S0 galaxies
are thicker and more circular than those in less massive spirals). The bar
intrinsic shape correlates with bulge, disc, and bar parameters. In particular
with the bulge-to-total (B/T) luminosity ratio, disc g-r color, and central
surface brightness of the bar, confirming the tight link between bars and their
host galaxies. Combining the probability distributions of the intrinsic shape
of bulges and bars in our sample we show that 52% (16%) of bulges are thicker
(flatter) than the surrounding bar at 1 level. We suggest that these
percentages might be representative of the fraction of classical and disc-like
bulges in our sample, respectively.Comment: 18 pages, 11 figures, accepted for publication in MNRA
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