A unique Fock quantization for fields in non-stationary spacetimes

In curved spacetimes, the lack of criteria for the construction of a unique quantization is a fundamental problem undermining the significance of the predictions of quantum field theory. Inequivalent quantizations lead to different physics. Recently, however, some uniqueness results have been obtained for fields in non-stationary settings. In particular, for vacua that are invariant under the background symmetries, a unitary implementation of the classical evolution suffices to pick up a unique Fock quantization in the case of Klein-Gordon fields with time-dependent mass, propagating in a static spacetime whose spatial sections are three-spheres. In fact, the field equation can be reinterpreted as describing the propagation in a Friedmann-Robertson-Walker spacetime after a suitable scaling of the field by a function of time. For this class of fields, we prove here an even stronger result about the Fock quantization: the uniqueness persists when one allows for linear time-dependent transformations of the field in order to account for a scaling by background functions. In total, paying attention to the dynamics, there exists a preferred choice of quantum field, and only one $SO(4)$-invariant Fock representation for it that respects the standard probabilistic interpretation along the evolution. The result has relevant implications e.g. in cosmology.Comment: Typos correcte

Influência de cultivar e nivel de infestação de Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) no rendimento do sorgo.

An experiment was conducted in the greenhouse to evaluate the effect of sorghum (Sorghum bicolor) cultivars and Spodoptera frugiperda (J.E.Smith) infestations, at different plant developmental stages, on sorghum yield. Second instar larvae of S. frugiperda were used to infest plants. Significant differences (P < 0.05) were found for the factors cultivar and stage of infestation for panicle (size and weight), grain (volume and weight) and 100 grain weight. No significant differences were observed for grain yield between damaged plant and the checks for the cvs. AG 3001 and CMSxs 375. However, the yields loss for the cv. BR 300 ranged from 11,6 to 21,7% for plants infested at 1st (15 days) and 4th stage (15 and 37 days), respectively

Probing doubly charged Higgs in e+e−e^+ e^- Colliders in 3-3-1 Model

The SU(3)_L\otimesU(1)_N electroweak model predicts new Higgs bosons beyond the one of the standard model. In this work we investigate the signature and production of doubly charged Higgs bosons in the $e^-e^+$ International Linear Collider and in the CERN Linear Collider. We compute the branching ratios for the doubly charged gauge bosons of the model.Comment: 17 pages, 12 figure

Study of the adhesion on overmoulded parts with thermoplastic/LSR combination

Multi-material parts with PBT/LSR combination were produced in two separate steps, one for the injection of PBT parts, and a second for the LSR overmoulding. The aim of this work is to study the influence of process-parameters such as mold temperature, curing time, temperature of the PBT insert before performing the overmoulding with LSR, on the adhesion with LSR’s. The effect on the adhesion of the amount of glass fiber content on the PBT was also studied. The adhesion between the materials was measured using a peel-test 90º. The results of the peel-test indicated that the adhesion is influenced by the parameters described. The adhesion between the two materials increase significantly with the increase of the processparameters

Applying knowledge management strategies to economic development in sub-Saharan Africa

Sustainability looks to achieve best outcomes for human and natural environments both now and in the indefinite future. It relates to the continuity of economic, social, institutional and environmental aspects of human society, as well as the non-human environment. This paper examines economic development as one aspect of sustainability, with a focus on knowledge management as an economic development strategy. Using Grey&rsquo;s categories of knowledge management, the authors address sustainable economic development in the context of sub-Saharan Africa. Production capability is no longer completely dependent on capital and equipment; information and knowledge assets are increasingly important. In this information economy, success comes from harnessing the information and knowledge of a community. Such &ldquo;indigenous knowledge,&rdquo; local and often tacit, exists in every community, every region and every country. This knowledge is useful in identifying new entrepreneurial opportunities, as well as for sustaining and advancing local businesses. Sub-Saharan Africa provides an excellent case study. No other region of the world is in more dire need of development. The 700 million people in this area face tremendous challenges, including the world&rsquo;s highest incidence of HIV/AIDS, deep poverty, unemployment, political instability, and a host of related problems. Key factors for using knowledge management as an economic development strategy in the region will include ICT (Information and Communication Technologies) literacy; uncovering and developing local intellectual assets; capturing tacit knowledge; internal and external knowledge sharing; and managing political, social and technological barriers. Other specific recommendations include promoting ICT literacy through training programs; leveraging internet and email technologies for community building; investing financial resources in R &amp; D; and developing metrics for outcome assessment.Keywords: Knowledge management, economic development, sub-Saharan Africa

Quantum Gowdy T3T^3 Model: Schrodinger Representation with Unitary Dynamics

The linearly polarized Gowdy $T^3$ model is paradigmatic for studying technical and conceptual issues in the quest for a quantum theory of gravity since, after a suitable and almost complete gauge fixing, it becomes an exactly soluble midisuperspace model. Recently, a new quantization of the model, possessing desired features such as a unitary implementation of the gauge group and of the time evolution, has been put forward and proven to be essentially unique. An appropriate setting for making contact with other approaches to canonical quantum gravity is provided by the Schr\"odinger representation, where states are functionals on the configuration space of the theory. Here we construct this functional description, analyze the time evolution in this context and show that it is also unitary when restricted to physical states, i.e. states which are solutions to the remaining constraint of the theory.Comment: 21 pages, version accepted for publication in Physical Review

Effect of the particle shape on flow through porous media

In order to study the performance of shaped particles flow in porous media, filtration of two different shape - spherical and rod-like – micro particles was performed through a porous bed. Filtration was investigated at a constant flow rate of 0.04 cm/s with yeast cells, diameter 5 microns, micro spheres, diameter 1 micron, and rod-like bacilli Lactobacillus bulgaricus with 6 microns average length and 0.5 micron diameter. Yeast diameter is close to the bacillus length and micro-sphere diameter is in the scale of the bacillus diameter. All particles have similar density. For the packing, the following glass beads were used: coarse particles, size 1.125 mm; fine particles, size 0.1115 mm. Experiments were carried out using a column loaded with a binary packing (volume fraction of coarse particles in the mixture 0.7) or with a monosize packing with the same amount of coarse or fine particles as used in the binary packing. The analysis of the experimental results was based on two models: pure exclusion effect and hydrodynamic separation model (HDC). Results for spheres show that the classic HDC model ( B = 1.0) fits well the data whenever the ratio of particle size to the bend scale is high (~ 1/100, as for micro spheres). However, if this ratio increases and becomes ~ 1/20, the HDC model needs to be corrected due to the effect of channel wall curvature on the exclusion effect. This assumption leads to a modified HDC equation - R = B/ (1+2λ -2.8λ²), where B ≥ 1 and λ represents the ratio of microparticle size to the pore size. The effect of pore topology plays an important role in the separation of shaped particles when the aspect ratio λ approaches 0.1 and, in the case of bacillus, separation occurs by an exclusion mechanism. For the binary packing, the rod-like particles behave differently from the spherical particles having a length or a diameter in the same scale of bacillus length and diameter. The explanation is the interference of rod-like particles with the pore topology. The exclusion model for particles was formulated in a general form as R = A/(1-λ)², where A is a coefficient proportional to the tortuosity and parameter z = 1, 2 or 3 depends mainly on the pore shape. For instance, in a parallel-plate channel flow: R ~ 1/(1-λ), for a cylindrical pore R ~ 1/(1-λ)² , and for 3-D pore R ~ 1/(1- λ)³ . Further investigation is needed to clarify the particle – pore topology interaction and its effect on particle separation

Screening in Anyon Gas

Anyon gas with interparticle (retarded) Coulomb interaction has been studied. The resulting system is shown to be a collection of dressed anyons, with a screening factor introduced in their spin. Close structural similarity with the Chern-Simons construction of anyons has helped considerably in computing the screening effect. Finally the present model is compared with the conventional Chern-Simons construction.Comment: 10 pages Late

Utilisation of controlled pore topology for the separation of bioparticles in a mixed-glass beads column

To study the flow of shaped particles in porous media, elution of spherical and rod-like micro-organisms was performed through beds of spherical glass beads. A 0.04 cm/s constant flow rate was used with 5 μm yeast suspensions, 1 μm latex micro-spheres and rod-like bacilli Lactobacillus bulgaricus 6 μm long and 0.5 μm in diameter. Yeast cells’ diameter is close to the bacilli length and micro-spheres have the same diameter as bacilli. All particle types have similar density. To make the different packing beds, 1.125 mm coarse beads and 0.1115 mm fine beads were used. Experiments were carried out using a column loaded with the binary packing (volume fraction of coarse particles in the mixture 0.7) or a monosize packing with the same amount of coarse or fine particles as used in the binary packing. Analysis of experimental results was based on two models: pure exclusion effect and hydrodynamic separation model [hydrodynamic chromatography (HDC)]. Results for spheres show that the classic HDC model fits to the experimental data whenever the ratio of particle size to the pathway bend scale is high (1/100, micro-spheres). However, if this ratio increases and becomes 1/20, the HDC model needs to be corrected due to the effect of channel wall curvature on exclusion. This led to a modified HDC equation of the form R = B/(1 + 2λ − 2.8λ2), where R is the retention, λ is the aspect ratio and constant B ≥ 1. Bacillus separation follows an exclusion mechanism, since pore topology is important in the separation of shaped particles when the aspect ratio approaches λ = 0.1. In the case of a binary packing bed, rod-like particles display a different behaviour than the one exhibited by the spherical particles of the same scale as bacilli, either in length or in diameter. This may be explained by the interaction between rod-like bacilli and the bed's pore topology. A generalised exclusion model for particles was proposed to be R = A/(1 − λ)z, where A is the coefficient proportional to the tortuosity and the parameter z = 1, 2 or 3 depends mainly on pore shape. Controlled pore topology opens interesting applications for bio-separation (in porous micro-fluidic devices, deep bed filtration) and might be especially important for macromolecules and micro-organisms separation with different shapes.Fundação para a Ciência e a Tecnologia (FCT