439 research outputs found
Constraints on Dimensional Warped Spaces
In order to investigate the phenomenological implications of allowing gauge
fields to propagate in warped spaces of more than five dimensions, we consider
a toy model of a space warped by the presence of a anisotropic bulk
cosmological constant. After solving the Einstein equation, three classes of
solutions are found, those in which the additional () dimensions are
growing, shrinking or remaining constant. It is found that gauge fields
propagating in these spaces have a significantly different Kaluza Klein (KK)
mass spectrum and couplings from that of the Randall and Sundrum model. This
leads to a greatly reduced lower bound on the KK scale, arising from
electroweak constraints, for spaces growing towards the IR brane.Comment: 6 pages, 5 figures PASCOS2010 International Symposium proceedin
Baryon Number in Warped GUTs : Model Building and (Dark Matter Related) Phenomenology
In the past year, a new non-supersymmetric framework for electroweak symmetry
breaking (with or without Higgs) involving SU(2)_L * SU(2)_R * U(1)_{B-L} in
higher dimensional warped geometry has been suggested. In this work, we embed
this gauge structure into a GUT such as SO(10) or Pati-Salam. We showed
recently (in hep-ph/0403143) that in a warped GUT, a stable Kaluza-Klein
fermion can arise as a consequence of imposing proton stability. Here, we
specify a complete realistic model where this particle is a weakly interacting
right-handed neutrino, and present a detailed study of this new dark matter
candidate, providing relic density and detection predictions. We discuss
phenomenological aspects associated with the existence of other light (<~ TeV)
KK fermions (related to the neutrino), whose lightness is a direct consequence
of the top quark's heaviness. The AdS/CFT interpretation of this construction
is also presented. Most of our qualitative results do not depend on the nature
of the breaking of the electroweak symmetry provided that it happens near the
TeV brane.Comment: 61 pages, 12 figures; v2: minor changes; v3: Two additional diagrams
in Fig. 10; a numerical factor corrected in section 16.1 (baryogenesis
section), corresponding discussion slightly modified but qualitative results
unchange
Mass and Gauge Invariance IV (Holography for the Karch-Randall Model)
We argue that the Karch-Randall compactification is holographically dual to a
4-d conformal field theory coupled to gravity on Anti de Sitter space. Using
this interpretation we recover the mass spectrum of the model. In particular,
we find no massless spin-2 states. By giving a purely 4-d interpretation to the
compactification we make clear that it represents the first example of a local
4-d field theory in which general covariance does not imply the existence of a
massless graviton. We also discuss some variations of the Karch-Randall model
discussed in the literature, and we examine whether its properties are generic
to all conformal field theory.Comment: 26 pages, uses package latexsym. Note added in proo
Interpolating between low and high energy QCD via a 5D Yang-Mills model
We describe the Goldstone bosons of massless QCD together with an infinite
number of spin-1 mesons. The field content of the model is SU(Nf)xSU(Nf)
Yang-Mills in a compact extra-dimension. Electroweak interactions reside on one
brane. Breaking of chiral symmetry occurs due to the boundary conditions on the
other brane, away from our world, and is therefore spontaneous. Our
implementation of the holographic recipe maintains chiral symmetry explicit
throughout. For intermediate energies, we extract resonance couplings. These
satisfy sum rules due to the 5D nature of the model. These sum rules imply,
when taking the high energy limit, that perturbative QCD constraints are
satisfied. We also illustrate how the 5D model implies a definite prescription
for handling infinite sums over 4D resonances. Taking the low energy limit, we
recover the chiral expansion and the corresponding non-local order parameters.
All local order parameters are introduced separately.Comment: Corresponds to published version, with some typos correcte
Transcriptional profiling of interleukin-2-primed human adipose derived mesenchymal stem cells revealed dramatic changes in stem cells response imposed by replicative senescence
Inflammation is a double-edged sword with both detrimental and
beneficial consequences. Understanding of the mechanisms of crosstalk
between the inflammatory milieu and human adult mesenchymal stem cells
is an important basis for clinical efforts. Here, we investigate changes
in the transcriptional response of human adipose-derived stem cells to
physiologically relevant levels of IL-2 (IL-2 priming) upon replicative
senescence. Our data suggest that replicative senescence might
dramatically impede human mesenchymal stem cell (MSC) function via
global transcriptional deregulation in response to IL-2. We uncovered a
novel senescence-associated transcriptional signature in human
adipose-derived MSCs hADSCs after exposure to pro-inflammatory
environment: significant enhancement of the expression of the genes
encoding potent growth factors and cytokines with anti-inflammatory and
migration-promoting properties, as well as genes encoding angiogenic and
antiapoptotic promoting factors, all of which could participate in the
establishment of a unique microenvironment. We observed transcriptional
up-regulation of critical components of the nitric oxide synthase
pathway (iNOS) in hADSCs upon replicative senescence suggesting, that
senescent stem cells can acquire metastasis-promoting properties via
stem cell-mediated immunosuppression. Our study highlights the
importance of age as a factor when designing cell-based or
pharmacological therapies for older patients and predicts measurable
biomarkers characteristic of an environment that is conducive to cancer
cells invasiveness and metastasis.LM and BGG was supported by grants from the Spanish Ministry of Science
and Innovation (SAF 2010-15239) to BGG and. LMP are supported by FPI
fellowships from the Spanish Ministry, and BGG acknowledges support from
the ``Ramon y Cajal´´ tenure track programme from the Spanish Ministry
of Science and Innovation (RYC2009-04669). AS and AA are fellows of
Bolashak International Scholarship, AA, AN, AS are sponsored by KazNMU
sponsored program.S
RS1, Higher Derivatives and Stability
We demonstrate the classical stability of the weak/Planck hierarchy within
the Randall-Sundrum scenario, incorporating the Goldberger-Wise mechanism and
higher-derivative interactions in a systematic perturbative expansion. Such
higher-derivative interactions are expected if the RS model is the low-energy
description of some more fundamental theory. Generically, higher derivatives
lead to ill-defined singularities in the vicinity of effective field theory
branes. These are carefully treated by the methods of classical
renormalization.Comment: 30 page
Gauge-gravity correspondence in de Sitter braneworld
We study the braneworld solutions based on a solvable model of 5d gauged
supergravity with two scalars of conformal dimension three, which correspond to
bilinear operators of fermions in the dual super Yang-Mills
theory on the boundary. An accelerating braneworld solution is obtained when
both scalars are taken as the form of deformations of the super Yang-Mills
theory and the bulk supersymmetry is broken. This solution is smoothly
connected to the Poincare invariant brane in the limit of vanishing
cosmological constant. The stability of this brane-solution and the
correspondence to the gauge theory are addressed.Comment: 16 pages, 1 figur
The structure of radiatively induced Lorentz and CPT violation in QED at finite temperature
We obtain the induced Lorentz- and CPT-violating term in QED at finite
temperature using imaginary-time formalism and dimensional regularization. Its
form resembles a Chern-Simons-like structure, but, unexpectedly, it does not
depend on the temporal component of the fixed constant vector that is
coupled to the axial current. Nevertheless Ward identities are respected and
its coefficient vanishes at T=0, consistently with previous computations with
the same regularization procedure, and it is a non-trivial function of
temperature. We argue that at finite a Chern-Simons-like Lorentz- and
CPT-violating term is generically present, the value of its coefficient being
unambiguously determined up to a independent constant, related to the
zero-temperature renormalization conditions.Comment: 15 pages, Latex, 1 figure in eps-format (included
Mechanisms linking excess adiposity and carcinogenesis promotion
Obesity constitutes one of the most important metabolic diseases being associated to insulin resistance development and increased cardiovascular risk. Association between obesity and cancer has also been well established for several tumor types, such as breast cancer in post-menopausal women, colorectal, and prostate cancer. Cancer is the first death cause in developed countries and the second one in developing countries, with high incidence rates around the world. Furthermore, it has been estimated that 15-20% of all cancer deaths may be attributable to obesity. Tumor growth is regulated by interactions between tumor cells and their tissue microenvironment. In this sense, obesity may lead to cancer development through dysfunctional adipose tissue and altered signaling pathways. In this review, three main pathways relating obesity and cancer development are examined: (i) inflammatory changes leading to macrophage polarization and altered adipokine profile; (ii) insulin resistance development; and (iii) adipose tissue hypoxia. Since obesity and cancer present a high prevalence, the association between these conditions is of great public health significance and studies showing mechanisms by which obesity lead to cancer development and progression are needed to improve prevention and management of these diseases
"Gaugomaly" Mediated SUSY Breaking and Conformal Sequestering
Anomaly-mediated supersymmetry breaking in the context of 4D conformally
sequestered models is combined with Poppitz-Trivedi D-type gauge-mediation. The
implementation of the two mediation mechanisms naturally leads to visible soft
masses at the same scale so that they can cooperatively solve the mu and flavor
problems of weak scale supersymmetry, as well as the tachyonic slepton problem
of pure anomaly-mediation. The tools are developed in a modular fashion for
more readily fitting into the general program of optimizing supersymmetric
dynamics in hunting for the most attractive weak scale phenomenologies combined
with Planck-scale plausibility.Comment: 14 pages, Late
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