76 research outputs found
Control of quantum fluctuations for a Yukawa interaction in the Kaluza Klein picture
We study a system of fermions interacting with a scalar field, in 4+1
dimensions where the 5th dimension is compactified, using an exact functional
method, where quantum fluctuations are controlled by the amplitude of the bare
fermion mass. The integration of our equationsleads to the properties of the
dressed Yukawa coupling, that we study at one-loop so as to show the
consistency of the approach. Beyond one loop, the non-perturbative aspect of
the method gives us the possibility to derive the dynamical fermion mass. The
result obtained is cut off independent and this derivation proposes an
alternative to the Schwinger-Dyson approach.Comment: extended discussion on the scalar effective potentia
Cosmology and Fermion Confinement in a Scalar-Field-Generated Domain Wall Brane in Five Dimensions
We consider a brane generated by a scalar field domain wall configuration in
4+1 dimensions, interpolating, in most cases, between two vacua of the field.
We study the cosmology of such a system in the cases where the effective
four-dimensional brane metric is de Sitter or anti de Sitter, including a
discussion of the bulk coordinate singularities present in the de-Sitter case.
We demonstrate that a scalar field kink configuration can support a brane with
dS cosmology, despite the presence of coordinate singularities in the
metric. We examine the trapping of fermion fields on the domain wall for
nontrivial brane cosmology.Comment: 29 pages, 12 figures; minor changes, accepted by JHE
Branon search in hadronic colliders
In the context of the brane-world scenarios with compactified extra
dimensions, we study the production of brane fluctuations (branons) in hadron
colliders (, and ) in terms of the brane tension
parameter , the branon mass and the number of branons . From the
absence of monojets events at HERA and Tevatron (run I), we set bounds on these
parameters and we also study how such bounds could be improved at Tevatron (run
II) and the future LHC. The single photon channel is also analyzed for the two
last colliders.Comment: 17 pages, 10 figures, LaTeX. New comments and figures included. Final
version to appear in Phys. Rev.
Gravitational Origin of Quark Masses and Mixings in an Extra-Dimensional Brane-World
Using the resolution of the gauge hierarchy problem recently proposed by
Randall and Sundrum, we find a natural explanation for the observed fermion
masses and mixings of the three Standard Model (SM) generations. Localizing
massless SM matter generations on neighboring 3-branes in an extra dimensional
world leads to effective four dimensional masses and mixings from the coupling
of the fermions with the background metric. We find that the positions of the
3-branes required to solve the gauge hierachy problem simultaneously reproduces
phenomenologically acceptable fermion masses and mixings.Comment: 10 pages, RevTex, psfig.sty, References adde
A Gravitational Potential with Extra-dimensions and Spin Effects In Hadronic Reactions
The impact of the KK-modes in d-brane models of gravity with large
compactification radii and TeV-scale quantum gravity on the hadronic potential
at small impact parameters is examined. The effects of the gravitational
hadronic form factors obtained from the generalized parton distributions (GPDs)
on the behavior of the gravitational potential and the possible spin
correlation effects are also analysed.Comment: 13 pages, 7 figure
Event shape discrimination of supersymmetry from large extra dimensions at a linear collider
The production of a charged lepton (e/mu) pair with a large missing energy at
a linear collider is discussed as a means of distinguishing the minimal
supersymmetry (MSSM) scenario from that with large extra dimensions (ADD) for
parameter ranges where the total cross sections are comparable for both.
Analyses in terms of event shape variables, specifically sphericity and thrust,
are shown to enable a clear discrimination in this regard.Comment: LaTex 13 pages, 11 figures, 1 table. Some clarifications and
additions are made and also results for CLIC include
Running Coupling with Minimal Length
In models with large additional dimensions, the GUT scale can be lowered to
values accessible by future colliders. Due to modification of the loop
corrections from particles propagating into the extra dimensions, the
logarithmic running of the couplings of the Standard Model is turned into a
power law. These loop-correction are divergent and the standard way to achieve
finiteness is the introduction of a cut-off. The question remains, whether the
results are reliable as they depend on an unphysical parameter.
In this paper, we show that this running of the coupling can be calculated
within a model including the existence of a minimal length scale. The minimal
length acts as a natural regulator and allows us to confirm cut-off
computations.Comment: 26 pages, 5 figures, typos corrected, replaced with published versio
Chemical characterization of a hypoglycemic extract from Cucurbita ficifolia bouche that induces liver glycogen accumulation in diabetic mice
Background: The aqueous extract of Cucurbita ficifolia (C. ficifolia) fruit has demonstrated hypoglycemic effect, which may be attributed to some components in the extract. However, the major secondary metabolites in this fruit have not yet been identified and little is known about its extra-pancreatic action, in particular, on liver carbohydrate metabolism. Therefore, in addition to the isolation and structural elucidation of the principal components in the aqueous extract of C. ficifolia, the aim of this study was to determine whether or not the hypoglycemic effect of the aqueous extract of Cucurbita ficifolia (C. ficifolia) fruit is due to accumulation of liver glycogen in diabetic mice.Materials and Methods: The aqueous extract from fruit of C. ficifolia was fractionated and its main secondary metabolites were purified and chemically characterized (NMR and GC-MS). Alloxan-induced diabetic mice received daily by gavage the aqueous extract (30 days). The liver glycogen content was quantified by spectroscopic method and by PAS stain; ALT and AST by spectrometric method; glycogen synthase, glycogen phosphorylase and GLUT2 by Western blot; the mRNA expression of GLUT2 and glucagon-receptor by RT-PCR; while serum insulin was quantified by ELISA method. A liver histological analysis was also performed by H&E stain.Results: Chemical fingerprint showed five majoritarian compounds in the aqueous extract of C. ficifolia: p-coumaric acid, p-hydroxybenzoic acid, salicin, stigmast-7,2,2-dien-3-ol and stigmast-7-en-3-ol. The histological analysis showed accumulation of liver glycogen. Also, increased glycogen synthase and decreased glycogen phosphorylase were observed. Interestingly, the histological architecture evidenced a liver-protective effect due the extract.Conclusion: Five compounds were identified in C. ficifolia aqueous extract. The hypoglycemic effect of this extract may be partially explained by liver glycogen accumulation. The bioactive compound responsible for the hypoglycemic effect of this extract will be elucidated in subsequent studies.Keywords: Cucurbita ficifolia, Cucurbitaceae, liver glycogen, hypoglycemic plants, p-coumaric acid, salicin, p-hydroxybenzoic aci
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