13,051 research outputs found
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
On the finiteness of the noncommutative supersymmetric Maxwell-Chern-Simons theory
Within the superfield approach, we prove the absence of UV/IR mixing in the
three-dimensional noncommutative supersymmetric Maxwell-Chern-Simons theory at
any loop order and demonstrate its finiteness in one, three and higher loop
orders.Comment: 9 pages, 2 figures, revtex
Canonical Quantization of the Maxwell-Chern-Simons Theory in the Coulomb Gauge
The Maxwell-Chern-Simons theory is canonically quantized in the Coulomb gauge
by using the Dirac bracket quantization procedure. The determination of the
Coulomb gauge polarization vector turns out to be intrincate. A set of quantum
Poincar\'e densities obeying the Dirac-Schwinger algebra, and, therefore, free
of anomalies, is constructed. The peculiar analytical structure of the
polarization vector is shown to be at the root for the existence of spin of the
massive gauge quanta.The Coulomb gauge Feynman rules are used to compute the
M\"oller scattering amplitude in the lowest order of perturbation theory. The
result coincides with that obtained by using covariant Feynman rules. This
proof of equivalence is, afterwards, extended to all orders of perturbation
theory. The so called infrared safe photon propagator emerges as an effective
propagator which allows for replacing all the terms in the interaction
Hamiltonian of the Coulomb gauge by the standard field-current minimal
interaction Hamiltonian.Comment: 21 pages, typeset in REVTEX, figures not include
Recomendações técnicas para o processamento de conservas de cogumelos comestÃveis.
Conservas de cogumelos: conservas de cogumelos esterilizados; conservas de cogumelos pasteurizados.bitstream/item/34412/1/2000-DOC-0043.pd
On the one-loop effective potential in the higher-derivative four-dimensional chiral superfield theory with a nonconventional kinetic term
We explicitly calculate the one-loop effective potential for a
higher-derivative four-dimensional chiral superfield theory with a
nonconventional kinetic term. We consider the cases of minimal and nonminimal
general Lagrangians. In particular, we find that in the minimal case the
divergent part of the one-loop effective potential vanishes by reason of the
chirality.Comment: 9 page
Os inventários de recursos hÃdricos subterrâneos como ferramenta de suporte à gestão dos recursos hÃdricos à escala local
Nos últimos anos a União Europeia produziu diversa legislação relativa aos recursos hÃdricos subterrâneos, tendo por base a sua preservação, conservação e gestão eficiente. Portugal transpôs e implementou estas orientações, incorporando assim a questão da proteção das águas subterrâneas no planeamento, nomeadamente à escala municipal.Este trabalho pretende evidenciar a utilidade dos inventários de emergências, bem como a sua relação com a análise de vulnerabilidade preconizada na Lei Portuguesa, constituindo assim, metodologias importantes de suporte à gestão destes importantes recursos, tanto a nÃvel municipal como local.Deste modo, apresentam-se os resultados de um inventário de recursos hÃdricos subterrâneos realizado na pequena bacia hidrográfica da Ribeira de Sá, localizada no concelho de Castelo de Paiva, em Portugal.Os resultados obtidos nesta área reforçam claramente a importância do conhecimento inicial dos recursos existentes, nomeadamente através da inventariação, para que se definam medidas proteção e gestão adequada
On the duality of three-dimensional superfield theories
Within the superfield approach, we consider the duality between the
supersymmetric Maxwell-Chern-Simons and self-dual theories in three spacetime
dimensions. Using a gauge embedding method, we construct the dual theory to the
self-dual model interacting with a matter superfield, which turns out to be not
the Maxwell-Chern-Simons theory coupled to matter, but a more complicated
model, with a ``restricted'' gauge invariance. We stress the difficulties in
dualizing the self-dual field coupled to matter into a theory with complete
gauge invariance. After that, we show that the duality, achieved between these
two models at the tree level, also holds up to the lowest order quantum
corrections.Comment: 18 pages,2 figures, revtex4, v2: corrected reference
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