7 research outputs found
de Sitter gauge theories and induced gravities
Pure de Sitter, anti de Sitter, and orthogonal gauge theories in
four-dimensional Euclidean spacetime are studied. It is shown that, if the
theory is asymptotically free and a dynamical mass is generated, then an
effective geometry may be induced and a gravity theory emerges. The asymptotic
freedom and the running of the mass might account for an In\"on\"u-Wigner
contraction which induces a breaking of the gauge group to the Lorentz group,
while the mass itself is responsible for the coset sector of the gauge field to
be identified with the effective vierbein. Furthermore, the resulting local
isometries are Lorentzian for the anti de Sitter group and Euclidean for the de
Sitter and orthogonal groups.Comment: Sections added. Text reviewed. References added. 14 pages, no
figures. Final version to appear in EPJ
The Gribov-Zwanziger action in the presence of the gauge invariant, nonlocal mass operator in the Landau gauge
We prove that the nonlocal gauge invariant mass dimension two operator
can be consistently added to the
Gribov-Zwanziger action, which implements the restriction of the path
integral's domain of integration to the first Gribov region when the Landau
gauge is considered. We identify a local polynomial action and prove the
renormalizability to all orders of perturbation theory by employing the
algebraic renormalization formalism. Furthermore, we also pay attention to the
breaking of the BRST invariance, and to the consequences that this has for the
Slavnov-Taylor identity.Comment: 30 page
Infinitesimal Gribov copies in gauge-fixed topological Yang-Mills theories
We study the Gribov problem in four-dimensional topological Yang-Mills
theories following the Baulieu-Singer approach in the (anti-)self-dual Landau
gauges. This is a gauge-fixed approach that allows to recover the topological
spectrum, as first constructed by Witten, by means of an equivariant (or
constrained) BRST cohomology. As standard gauge-fixed Yang-Mills theories
suffer from the gauge copy (Gribov) ambiguity, one might wonder if and how this
has repercussions for this analysis. The resolution of the small
(infinitesimal) gauge copies, in general, affects the dynamics of the
underlying theory. In particular, treating the Gribov problem for the standard
Landau gauge condition in non-topological Yang-Mills theories strongly affects
the dynamics of the theory in the infrared. In the current paper, although the
theory is investigated with the same gauge condition, the effects of the copies
turn out to be completely different. In other words: in both cases, the copies
are there, but the effects are very different. As suggested by the tree-level
exactness of the topological model in this gauge choice, the Gribov copies are
shown to be inoffensive at the quantum level. To be more precise, following
Gribov, we discuss the path integral restriction to the Gribov horizon. The
associated gap equation, which fixes the so-called Gribov parameter, is however
shown to only possess a trivial solution, making the restriction obsolete. We
relate this to the absence of radiative corrections in both gauge and ghost
sectors. We give further evidence by employing the renormalization group which
shows that, for this kind of topological model, the gap equation indeed forbids
the introduction of a massive Gribov parameter.Comment: 21 pages. Final version accepted for publication in Physics Letters
Quadratic curvature terms and deformed Schwarzschildâde Sitter black hole analogues in the laboratory
Sound waves on a fluid stream, in a de Laval nozzle, are shown to correspond to quasinormal modes emitted by black holes that are physical solutions in a quadratic curvature gravity with cosmological constant. Sound waves patterns in transsonic regimes at a laboratory are employed here to provide experimental data regarding generalized theories of gravity, comprised by the exact de Sitter-like solution and a perturbative solution around the Schwarzschildâde Sitter standard solution as well. Using the classical tests of General Relativity to bound free parameters in these solutions, acoustic perturbations on fluid flows in nozzles are then regarded, to study quasinormal modes of these black holes solutions, providing deviations of the de Laval nozzle cross-sectional area, when compared to the Schwarzschild solution. The fluid sonic point in the nozzle, for sound waves in the fluid, is shown to implement the acoustic event horizon corresponding to quasinormal modes. Keywords: Black holes, Fluid branes, Fluid dynamics, Quadratic curvature gravity, de Laval nozzl
Atividade antibacteriana in vitro de extratos de alho nirá (Allium tuberosum Rottler ex Spreng.)
Com o objetivo de demonstrar a influência da condimentação sobre a Validade Preditiva dos Resultados Negativos do diagnóstico de bactérias transmissÃveis por alimentos, determinou-se, in vitro, a intensidade de atividade de inibição bacteriana (IINIB) e a intensidade de atividade de inativação bacteriana (IINAB) de três acessos de Allium tuberosum Rottler ex Spreng. - Liliaceae - alho "nirá", originários da região metropolitana de Porto Alegre, Rio Grande do Sul. O extrato etanólico à 50% destes diferentes acessos (alcoolaturas com evaporação do etanol em sistema rotavapor com reconstituição hÃdrica sob assepsia) foi testado, através de testes de diluição em sistema de tubos múltiplos, sobre inóculos padronizados de Staphylococcus aureus (ATCC 25.923), Enterococcus faecalis (ATCC 19.433), Salmonella enteritidis (ATCC 11.076), Escherichia coli (ATCC 11.229). Os testes revelaram atividade antibacteriana seletiva sobre os diferentes inóculos Gram-negativos, que atingiram inibição e inativação máximas e permanentes para Salmonella após 48 horas, e, para Escherichia coli, após 72 horas de exposição. As bactérias Gram-positivas, Staphylococcus e Enterococcus, apresentaram resistência total frente aos extratos etanólicos Não houve diferença significativa entre si quanto aos tempos de atuação, quanto a Salmonella e Escherichia, quanto à presença ou ausência de desinibidores bacterianos, havendo, entretanto, diferença significativa entre os acessos de alho nirá