3,263 research outputs found
Bosonized noncommutative bi-fundamental fermion and S-duality
We perform the path-integral bosonization of the recently proposed
noncommutative massive Thirring model (NCMT) [JHEP0503(2005)037]. This
model presents two types of current-current interaction terms related to the
bi-fundamental representation of the group U(1). Firstly, we address the
bosonization of a bi-fundamental free Dirac fermion defined on a noncommutative
(NC) Euclidean plane \IR_{\theta}^{2}. In this case we show that the fermion
system is dual to two copies of the NC Wess-Zumino-Novikov-Witten model. Next,
we apply the bosonization prescription to the NCMT model living on
\IR_{\theta}^{2} and show that this model is equivalent to two-copies of the
WZNW model and a two-field potential defined for scalar fields corresponding to
the global symmetry plus additional bosonized terms for the
four fermion interactions. The bosonic sector resembles to the one proposed by
Lechtenfeld et al. [Nucl. Phys. B705(2005)477] as the noncommutative
sine-Gordon for a {\sl pair} of scalar fields. The bosonic and fermionic
couplings are related by a strong-weak duality. We show that the couplings of
the both sectors for some representations satisfy similar relationships up to
relevant re-scalings, thus the NC bi-fundamental couplings are two times the
corresponding ones of the NC fundamental (anti-fundamental) and eight times the
couplings of the ordinary massive Thirring and sine-Gordon models.Comment: 18 pages, LaTex. References added. A general product has been considered in the conclusion section . Version to appear in
JHE
Exploring singlet deflection of gauge mediation
We embed the Next-to Minimal Supersymmetric Standard Model into gauge
mediation of supersymmetry breaking and study the phenomenology of scenarios
where the gauge-mediation contributions to soft parameters are deflected by
superpotential interactions of the gauge singlet with the messenger fields and
the Higgs doublets. This kind of models provide a satisfactory solution to the
mu-b_mu problem of gauge mediation, compatible with the adequate pattern of
electroweak symmetry breaking and a realistic spectrum with supersymmetric
partners at the TeV scale without requiring a significant fine tuning.Comment: Latex 18 pages, 4 eps figures. Minor corrections, version published
in Phys. Rev.
Modulation of TGF-beta signaling by proinflammatory cytokines in articular chondrocytes.
OBJECTIVE: The normal structure and function of articular cartilage are the result of a precisely balanced interaction between anabolic and catabolic processes. The transforming growth factor-beta (TGF-beta) family of growth factors generally exerts an anabolic or repair response; in contrast, proinflammatory cytokines such as interleukin 1 beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) exert a strong catabolic effect. Recent evidence has shown that IL-1beta, and TNF-alpha, and the TGF-beta signaling pathways share an antagonistic relationship. The aim of this study was to determine whether the modulation of the response of articular chondrocytes to TGF-beta by IL-1beta or TNF-alpha signaling pathways occurs through regulation of activity and availability of mothers against DPP (Drosophila) human homologue (Smad) proteins.
METHODS: Human articular chondrocytes isolated from knee joints from patients with osteoarthritis (OA) or normal bovine chondrocytes were cultured in suspension in poly-(2-hydroxyethyl methacrylate)-coated dishes with either 10% fetal bovine serum media or serum-deprived media 6h before treatment with IL-1beta alone, TNF-alpha alone or IL-1beta followed by TGF-beta. Nuclear extracts were examined by electrophoretic mobility-shift assays (EMSA) for nuclear factor-kappa B (NF-kappaB) and Smad3/4 deoxyribonucleic acid (DNA) binding. Nuclear extracts were also subjected to the TranSignal Protein/DNA array (Panomics, Redwood City, CA) enabling the simultaneous semiquantitative assessment of DNA-binding activity of 54 different transcription factors. Nuclear phospho-Smad2/3 and total Smad7 protein expression in whole cell lysates were studied by Western blot. Cytoplasmic Smad7, type II collagen alpha 1 (COL2A1), aggrecan and SRY-related high mobility group-Box gene 9 (SOX-9) mRNA expression were measured by real-time polymerase chain reaction (PCR).
RESULTS: The DNA-binding activity of Smad3/4 in the TranSignal Protein/DNA array was downregulated by TNF-alpha (46%) or IL-1beta treatment (42%). EMSA analysis showed a consistent reduction in Smad3/4 DNA-binding activity in human articular chondrocytes treated with IL-1beta or TNF-alpha. TGF-beta-induced Smad3/4 DNA-binding activity and Smad2/3 phosphorylation were also reduced following pretreatment with IL-1beta in human OA and bovine chondrocytes. Real-time PCR and Western blot analysis showed that IL-1beta partially reversed the TGF-beta stimulation of Smad7 mRNA and protein levels in TGF-beta-treated human OA cells. In contrast, TGF-beta-stimulated COL2A1, aggrecan, and SOX-9 mRNA levels were abrogated by IL-1beta.
CONCLUSIONS: IL-1beta or TNF-alpha exerted a suppressive effect on Smad3/4 DNA-binding activity in human articular chondrocytes, as well as on TGF-beta-induced stimulation of Smad3/4 DNA-binding activity and Smad2/3 phosphorylation in human OA and bovine articular chondrocytes. IL-1beta partially reversed the increase in TGF-beta-stimulated Smad7 mRNA or protein levels suggesting that Smad7 may not be involved in the suppression of TGF-beta signaling induced by IL-1beta or TNF-alpha in articular chondrocytes. The balance between the IL-1beta or TNF-alpha and the TGF-beta signaling pathways is crucial for maintenance of articular cartilage homeostasis and its disruption likely plays a substantial role in the pathogenesis of OA
Affine Toda model coupled to matter and the string tension in QCD
The affine Toda model coupled to matter (ATM) is shown to describe
various features, such as the spectrum and string tension, of the low-energy
effective Lagrangian of QCD (one flavor and colors). The
corresponding string tension is computed when the dynamical quarks are in the
{\sl fundamental} representation of SU(N) and in the {\sl adjoint}
representation of SU(2).Comment: LaTex, 10 pages. Revised version to appear in Phys. Rev.
Indirect Effect of Supersymmetric Triplets in Stop Decays
We study an extension of the minimal supersymmetric standard model with a
zero hypercharge triplet, and the effect that such a particle has on stop
decays. This model has the capability of predicting a 125.5 GeV Higgs even in
the presence of light stops and it can modify the diphoton rate by means of the
extra charged fermion triplet coupled to the Higgs. Working in the limit where
the scalar triplet decouples, and with small values of mA, we find that the
fermion triplet can greatly affect the branching ratios of the stops, even in
the absence of a direct stop-triplet coupling. We compare the triplet extension
with the MSSM and discuss how the additional fields affect the search for stop
pair production.Comment: pdfLateX, 16 pages, 7 figures, 2 tables, Typos, minor changes.
Version published in JHE
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