7,579 research outputs found
Thick Braneworlds and the Gibbons-Kallosh-Linde No-go Theorem in the Gauss-Bonnet Framework
The sum rules related to thick braneworlds are constructed, in order to
encompass Gauss-Bonnet terms. The generation of thick branes is hence proposed
in a periodic extra dimension scenario, what circumvents the
Gibbons-Kallosh-Linde no-go theorem in this context.Comment: 6 pages, to appear in the EPL. arXiv admin note: text overlap with
arXiv:1406.632
Five-Dimensional f(R) Braneworld Models
After incorporating the f(R) gravity into the general braneworld sum rules
scope, it is shown that some particular class of warped five dimensional
nonlinear braneworld models, which may be interesting for the hierarchy problem
solution, still require a negative tension brane. For other classes of warp
factors (suitable and not suitable for approaching the hierarchy problem) it is
not necessary any negative brane tension in the compactification scheme. In
this vein, it is argued that in the bulk f(R) gravity context, some types of
warp factors may be useful for approaching the hierarchy problem and for
evading the necessity of a negative brane tension in the compactification
scheme.Comment: 10 pages, references updated, small modifications. Accepted for
publication in Phys. Rev.
Braneworlds scenarios in a gravity model with higher order spatial three-curvature terms
In this work we study a Horava-like five-dimensional model in the context of
braneworld theory. To begin with, the equations of motion of such model are
obtained and, within the realm of warped geometry, we show that the model is
consistent if and only if takes its relativistic value 1.
Furthermore, since the first derivative of the warp factor is discontinuous
over the branes, we show that the elimination of problematic terms involving
the square of the warp factor second order derivatives are eliminated by
imposing detailed balance condition in the bulk. Afterwards, the Israel's
junction conditions are computed, allowing the attainment of an effective
Lagrangian in the visible brane. In particular, for a (4+1)-dimensional
Horava-like model defined in the bulk without cosmological constant, we show
that the resultant effective Lagrangian in the brane corresponds to a
(3+1)-dimensional Horava-like model with an emergent positive cosmological
constant but without detailed balance condition. Now, restoration of detailed
balance condition, at this time imposed over the brane, plays an interesting
role by fitting accordingly the sign of the arbitrary constant that
labels the extra terms in the model, insuring a positive brane tension and a
real energy for the graviton within its dispersion relation. To end up with,
the brane consistency equations are obtained and, as a result, we show that the
detailed balance condition again plays an essential role in eliminating bad
behaving terms and that the model admits positive brane tensions in the
compactification scheme if, and only if, is negative, what is in
accordance with the previous result obtained for the visible brane.Comment: 23 pages, 1 figure, title modifie
Searching for Elko dark matter spinors at the CERN LHC
The aim of this work is to explore the possibility to discover a fermionic
field with mass dimension one, the Elko field, in the Large Hadron Collider
(LHC). Due to its mass dimension, an Elko can only interact either with
Standard Model (SM) spinors and gauge fields at 1-loop order or at tree level
through a quartic interaction with the Higgs field. In this Higgs portal
scenario, the Elko is a viable candidate to a dark matter constituent which has
been shown to be compatible with relic abundance measurements from WMAP and
direct dark matter--nucleon searches. We propose a search strategy for this
dark matter candidate in the channel at
the TeV LHC. We show the LHC potential to discover the Elko
considering a triple Higgs-Elko coupling as small as after 1
pb of integrated luminosity. Some phenomenological consequences of this
new particle and its collider signatures are also discussed.Comment: 7 pages, 3 figure
Constraining Elko Dark Matter at the LHC with Monophoton Events
A mass dimension one fermion, also known as Elko, constitutes a dark matter
candidate which might interact with photons at the tree level in a specific
fashion. In this work, we investigate the constraints imposed by unitarity and
LHC data on this type of interactions using the search for new physics in
monophoton events. We found that Elkos which can explain the dark matter relic
abundance mainly through electromagnetic interactions are excluded at the
95\%CL by the 8 TeV LHC data for masses up to 1 TeV.Comment: 6 pages, 4 figure
Effective lagrangian for a mass dimension one fermionic field in curved spacetime
In this work we use momentum-space techniques to evaluate the propagator
for a spin mass dimension one spinor field on a curved
Friedmann-Robertson-Walker spacetime. As a consequence, we built the one-loop
correction to the effective lagrangian in the coincidence limit. Going further
we compute the effective lagrangian in the finite temperature regime. We arrive
at interesting cosmological consequences, as time-dependent cosmological
`constant', fully explaining the functional form of previous cosmological
models.Comment: 9 pages, 0 figure
Influência de parâmetros ambientais sobre a comunidade de peixes de um afluente da margem esquerda do Rio Amazonas, Amazônia Oriental.
A distribuição de espécies sempre foi a preocupação central da ecologia. Este estudo visa compreender a relação de fatores abióticos que podem afetar a distribuição especial e sazonal da ictiofauna do rio Matapi um afluente da margem esquerda do rio Amazonas na região central do estado do Amapá, região da Amazônia Oriental, em um percurso de aproximadamente 90 km de extensão. Os peixes foram coletados bimensalmente durante um ciclo anual, utilizando rede de emalhar de diferentes tamanhos, matapis, tarrafas, linhas de mão e espinhel de fundo, em um raio de 1000 metros. Também o pH, condutividade elétrica, sólidos suspensos, transparência e outros fatores secundários como profundidade e largura do rio foram mensurados. Análise de variância com dois fatores (ANOVA- Two-way) foi usada para testar as diferenças espaciais e temporais para os fatores abióticos analisados. Foram identificadas 105 espécies, mas apenas as espécies com frequência a partir de 0,5% fizeram parte da analise, de forma que somente 29 espécies foram usadas. As matrizes foram submetidas à analise multivariada de ordenação (Co-inércia) para encontrar padrões na estrutura da ictiofauna relacionados aos diferentes fatores abióticos investigados. Os resultados indicaram parâmetros ambientais não mostraram diferenças sazonais, mas sim entre áreas de coleta. Já a ictiofauna mostrou diferenças tanto sazonal como espacial. Análise de co-inércia sumarizou eficientemente que a estrutura da ictiofauna e dos fatores ambientais ocorreram espacialmente, independentemente da sazonalidade e que os fatores determinantes dessa distribuição foram a transparência, condutividade, largura do rio e sólidos suspensos.Esses estudos podem contribuir para orientar a gestão ambiental e esforços de conservação ao longo desse importante tributário do rio Amazonas.CB19
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