20,945 research outputs found
Graviton resonances on two-field thick branes
This work presents new results about the graviton massive spectrum in
two-field thick branes. Analyzing the massive spectra with a relative
probability method we have firstly showed the presence of resonance structures
and obtained a connection between the thickness of the defect and the lifetimes
of such resonances. We obtain another interesting results considering the
degenerate Bloch brane solutions. In these thick brane models, we have the
emergence of a splitting effect controlled by a degeneracy parameter. When the
degeneracy constant tends to a critical value, we have found massive resonances
to the gravitational field indicating the existence of modes highly coupled to
the brane. We also discussed the influence of the brane splitting effect over
the resonance lifetimes.Comment: 15 pages, 8 figure
Gravity localization on hybrid branes
This work deals with gravity localization on codimension-1 brane worlds
engendered by compacton-like kinks, the so-called hybrid branes. In such
scenarios, the thin brane behaviour is manifested when the extra dimension is
outside the compact domain, where the energy density is non-trivial, instead of
asymptotically as in the usual thick brane models. The zero mode is trapped in
the brane, as required. The massive modes, although are not localized in the
brane, have important phenomenological implications such as corrections to the
Newton's law. We study such corrections in the usual thick domain wall and in
the hybrid brane scenarios. By means of suitable numerical methods, we attain
the mass spectrum for the graviton and the corresponding wavefunctions. The
spectra possess the usual linearly increasing behaviour from the Kaluza-Klein
theories. Further, we show that the 4D gravitational force is slightly
increased at short distances. The first eigenstate contributes highly for the
correction to the Newton's law. The subsequent normalized solutions have
diminishing contributions. Moreover, we find out that the phenomenology of the
hybrid brane is not different from the usual thick domain wall. The use of
numerical techniques for solving the equations of the massive modes is useful
for matching possible phenomenological measurements in the gravitational law as
a probe to warped extra dimensions.Comment: 15 pages, 11 figure
Antisymmetric tensor propagator with spontaneous Lorentz violation
In this work, we study the spontaneous Lorentz symmetry breaking due to an
antisymmetric 2-tensor field in Minkowski spacetime. For a smooth quadratic
potential, the spectrum of the theory exhibits massless and massive
excitations. We show that the equations of motion for the free field obey some
constraints which lead to the massive mode be non-propagating at leading order.
Besides, there exists a massless mode in the theory which can be identified
with the usual Kalb-Ramond field, carrying only one on-shell degree of freedom.
The same conclusion holds when one analyses the pole structure of its Feynman
propagator. A new complete set of spin-type operators is found, which was the
requirement to evaluate the propagator of the Kalb-Ramond field modified by the
presence of a nonzero vacuum expectation value responsible for the Lorentz
violation.Comment: 13 pages. Some modifications to match published version in
EuroPhysics Letter
Determining the Chirality of Yukawa Couplings via Single Charged Higgs Boson Production in Polarized Photon Collision
When the charged Higgs boson is too heavy to be produced in pairs, the
predominant production mechanism at Linear Colliders is via the single charged
Higgs boson production processes, such as and . We show that
the yield of a heavy charged Higgs boson at a collider is
typically one or two orders of magnitude larger than that at an
collider. Furthermore, a polarized collider can determine the
chirality of the Yukawa couplings of fermions with charged Higgs boson via
single charged Higgs boson production, and thus discriminate models of new
physics.Comment: Version accepted by Physical Review Letters (references added, minor
rewording, RevTex4
Efeito da aplicação de tratamentos pós-colheita na conservação de raízes de mandioca.
O objetivo deste trabalho foi avaliar a eficiência do revestimento com fécula de mandioca ou parafina na conservação da qualidade pós-colheita de raízes de mandioca armazenadas sob condições ambiente por 9 dias. Após a lavagem e sanitização, as raízes foram revestidas com fécula de mandioca na concentração de 5% ou parafina aquecida a 60 oC e acomodadas em bandejas de poliestireno expandido ? EPS (Isopor®) mantidas sob temperatura ambiente. Como controle foram utilizadas raízes sem recobrimento. As análises foram realizadas diariamente, durante 9 dias de armazenamento, sendo avaliada a perda de massa, tempo de cozimento, aparência visual, umidade, pH e acidez titulável. Por meio de identificação visual, observou-se que o escurecimento vascular foi o principal sintoma de deterioração nas mandiocas. Nas raízes que não sofreram qualquer tratamento e naquelas submetidas ao tratamento com revestimento de fécula, os sintomas de deterioração apareceram no terceiro dia de armazenamento, em cerca de 50% das raízes. Nas mandiocas submetidas ao tratamento com revestimento de parafina, os primeiros sintomas internos foram observados no quarto dia de armazenamento, em 33,3% das raízes analisadas. O revestimento com parafina foi responsável também por menor perda de massa e menor tempo de cozimento das raízes ao longo de todo o período de armazenamento. Para a análise de umidade, observaram-se teores variando de 57,9% a 64,7%. Para as análises de pH e acidez titulável verificou-se oscilação nos resultados ao longo do período de armazenamento para os três tratamentos estudados.bitstream/item/31764/1/BPD74.pdfVersão eletrônica. 1ª impressão: 2010
Free Fields for Chiral 2D Dilaton Gravity
We give an explicit canonical transformation which transforms a generic
chiral 2D dilaton gravity model into a free field theory.Comment: LaTeX file, 4 pages, to appear in Phys. Rev.
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