6,262 research outputs found
Mass generation for non-Abelian antisymmetric tensor fields in a three-dimensional space-time
Starting from a recently proposed Abelian topological model in (2+1)
dimensions, which involve the Kalb-Ramond two form field, we study a
non-Abelian generalization of the model. An obstruction for generalization is
detected. However we show that the goal is achieved if we introduce a vectorial
auxiliary field. Consequently, a model is proposed, exhibiting a non-Abelian
topological mass generation mechanism in D=3, that provides mass for the
Kalb-Ramond field. The covariant quantization of this model requires ghosts for
ghosts. Therefore in order to quantize the theory we construct a complete set
of BRST and anti-BRST equations using the horizontality condition.Comment: 8 pages. To appear in Physical Review
Non-Chern-Simons Topological Mass Generation in (2+1) Dimensions
By dimensional reduction of a massive BF theory, a new topological field
theory is constructed in (2+1) dimensions. Two different topological terms, one
involving a scalar and a Kalb-Ramond fields and another one equivalent to the
four-dimensional BF term, are present. We constructed two actions with these
topological terms and show that a topological mass generation mechanism can be
implemented. Using the non-Chern-Simons topological term, an action is proposed
leading to a classical duality relation between Klein-Gordon and Maxwell
actions. We also have shown that an action in (2+1) dimensions with the
Kalb-Ramond field is related by Buscher's duality transformation to a massive
gauge-invariant Stuckelberg-type theory.Comment: 8 pages, no figures, RevTE
Experimental Demonstration of a Structured Material with Extreme Effective Parameters at Microwaves
Following our recent theoretical studies [M. G. Silveirinha, C. A. Fernandes,
Phys. Rev. B, 78, 033108, 2008], it is experimentally verified that an array of
crossed metallic wires may behave as a nonresonant material with extremely
large index of refraction at microwaves, and may enable the realization of
ultra-subwavelength waveguides.Comment: accepted for publication in Applied Physics Letters (in press).
Applied Physics Letters (in press) (2008
Fatty acid profile of cheese from dairy goats fed a diet enriched with castor, sesame and faveleira vegetable oils.
Abstract: The addition of vegetable oils to the diets of dairy goats is an alternative to supplemental feeding during the dry period and improves the lipid profile of milk and by-products. Cheeses were produced using milk from cross bred goats (SaanenĂ—Alpina) fed diets enriched with 4% vegetable oil (faveleira, sesame or castor), the fatty acid profile of cheeses was studied. Supplementation with vegetable oils did not increase the total fat percentage of the cheese (p?0.05) but did increase the percentage of CLA isomers, long-chain fatty acids (LCFA) and polyunsaturated fatty acids (PUFA); in addition, the index of desirable fatty acids (DFA--expressed as the sum of unsaturated fatty acids plus stearic acid) was increased for cheese made from milk from goats fed sesame or faveleira oil. Cheeses may have had increased percentages of cis-9,trans-11-CLA due to the supplementation of animal diets with vegetable oils rich in C18:2, such as faveleira and sesame oils. The fatty acid profile of goat cheese did not change significantly in response to the use of castor oil. Thus, the addition of sesame and faveleira oils to goat diets positively altered the fatty acid profile, which improved the nutritional characteristics of the fat present in goat cheese
Four-dimensional topological Einstein-Maxwell gravity
The complete on-shell action of topological Einstein-Maxwell gravity in
four-dimensions is presented. It is shown explicitly how this theory for SU(2)
holonomy manifolds arises from four-dimensional Euclidean N=2 supergravity. The
twisted local BRST symmetries and twisted local Lorentz symmetries are given
and the action and stress tensor are shown to be BRST-exact. A set of
BRST-invariant topological operators is given. The vector and antisymmetric
tensor twisted supersymmetries and their algebra are also found.Comment: Published version. Expanded discussion of new results in the
introduction and some clarifying remarks added in later sections. 22 pages,
uses phyzz
Talking with and about politicians on Twitter:An analysis of tweets containing @-mentions of candidates in the Brazilian presidential elections
Simultaneous Localization and Mapping (SLAM) of a Mobile Robot Based on Fusion of Odometry and Visual Data Using Extended Kalman Filter
Non
Controle de plantas daninhas na cultura do morangueiro com cobertura do solo.
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