563 research outputs found
Strong-Electroweak Unification at About 4 TeV
It is shown how an nonsupersymmetric quiver gauge theory can
accommodate the standard model with three chiral families and unify all of
, and couplings with high accuracy at one unique
scale estimated as TeV.Comment: 3 pages LaTeX. Typos corrected. Text and references adde
Charmonium sum rules applied to a holographic model
The heavy-quark QCD sum rules are applied to a model of charmonium based upon
the gauge/gravity duality. We find that there is strong agreement between the
moments of the polarization function calculated from the holographic model and
the experimental data suggesting that the model is consistent with the
heavy-quark QCD sum rules at zero temperature.Comment: 9 pages, 2 figures, Corrected typos to bring inline with PRD versio
Shining a Gluon Beam Through Quark-Gluon Plasma
We compute the energy density radiated by a quark undergoing circular motion
in strongly coupled supersymmetric Yang-Mills plasma. If it
were in vacuum, this quark would radiate a beam of strongly coupled radiation
whose angular distribution has been characterized and is very similar to that
of synchrotron radiation produced by an electron in circular motion in
electrodynamics. Here, we watch this beam of gluons getting quenched by the
strongly coupled plasma. We find that a beam of gluons of momenta is attenuated rapidly, over a distance in
a plasma with temperature . As the beam propagates through the plasma at the
speed of light, it sheds trailing sound waves with momenta .
Presumably these sound waves would thermalize in the plasma if they were not
hit soon after their production by the next pulse of gluons from the
lighthouse-like rotating quark. At larger and larger , the trailing sound
wave becomes less and less prominent. The outward going beam of gluon radiation
itself shows no tendency to spread in angle or to shift toward larger
wavelengths, even as it is completely attenuated. In this regard, the behavior
of the beam of gluons that we analyze is reminiscent of the behavior of jets
produced in heavy ion collisions at the LHC that lose a significant fraction of
their energy without appreciable change in their angular distribution or their
momentum distribution as they plow through the strongly coupled quark-gluon
plasma produced in these collisions.Comment: 16 pages, 4 figure
A new type of lordosis and vertebral body compression in Gilthead seabream, Sparus aurata Linnaeus, 1758: aetiology, anatomy and consequences for survival
A new type of vertebral malformation is described, consisting of deformed cartilaginous neural and haemal processes and the compression and fusion of vertebral bodies. The malformation is designated as haemal vertebral compression and fusion (haemal VCF). We studied the aetiology of the malformations and described microanatomical histopathological alterations. The malformations were detected during routine quality control in one of six monitored Gilthead sea bream populations. Haemal VCF affected the posterior part of the vertebral column (haemal vertebrae). In 20% of the deformed specimens, haemal VCF was combined with lordosis. At 35dph (days post-hatching), early anatomical signs of the haemal VCF consisted of abnormal centrum mineralization, malformed cartilaginous neural and haemal processes and developing lordotic alterations. The histological examination of the deformed individuals revealed that haemal VCF is preceded by notochord abnormalities. The frequency of deformed individuals was three times higher at 35 than at 61dph (50.3% vs. 17.2%, n=157 and n=250, respectively). No signs of repair or reversion of malformations have been observed. Thus, the steep decrease in deformities in older animals suggests that haemal VCF is linked to high mortality rates. The results are discussed in respect of the possible causative factors of haemal VCF
Type IIB orientifolds with discrete torsion
We consider compact four-dimensional type IIB
orientifolds, for certain values of and . We allow the additional
feature of discrete torsion and discuss the modification of the consistency
conditions arising from tadpole cancellation. We point out the differences
between the cases with and without discrete torsion.Comment: 4 pages LaTeX. Write-up of talk at DPF2000, Columbus, OH, August 10,
2000. References adde
Unification with Enlarged Kaluza-Klein Dimensions
In minimal theories with extra spatial dimensions at scales mu_0 much lower
than the conventional GUT scale, unification can give too-large predictions for
alpha_3(M_Z) given alpha_1(M_Z) and alpha_2(M_Z) as empirical input. We
systematically study the effects of adding extra states above the
compactification scale on running of the gauge couplings and find several
simple examples that give unification where all alpha_i(M_Z) are consistent
with low-energy data. We study both the supersymmetric and nonsupersymmetric
unification.Comment: 18 pages, LaTeX, analysis for the susy case takes into account that
extra hypermultiplets come in conjugate pairs, minor changes in text and
references, to be published in Phys. Lett.
Holographic gauge mediation via strongly coupled messengers
We consider a relative of semi-direct gauge mediation where the hidden sector
exists at large 't Hooft coupling. Such scenarios can be difficult to describe
using perturbative field theory methods but may fall into the class of
holographic gauge mediation scenarios, meaning that they are amenable to the
techniques of gauge/gravity duality. We use a recently found gravity solution
to examine one such case where the hidden sector is a cascading gauge theory
resulting in a confinement scale not much smaller than the messenger mass. In
the original construction of holographic gauge mediation, as in other examples
of semi-direct gauge mediation at strong coupling, the primary contributions to
visible sector soft terms come from weakly coupled messenger mesons. In
contrast to these examples, we describe the dual of a gauge theory where there
are significant contributions from scales where the strongly coupled messenger
quarks are the effective degrees of freedom. In this regime, the visible sector
gaugino mass can be calculated entirely from holography.Comment: 42 pages, 3 figures, references added, typos and minor errors
correcete
Conformal symmetry of brane world effective actions
A simple derivation of the low-energy effective action for brane worlds is
given, highlighting the role of conformal invariance. We show how to improve
the effective action for a positive- and negative-tension brane pair using the
AdS/CFT correspondence.Comment: 5 pages, published versio
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