Some boundary effects in quantum field theory

We have constructed a quantum field theory in a finite box, with periodic boundary conditions, using the hypothesis that particles living in a finite box are created and/or annihilated by the creation and/or annihilation operators, respectively, of a quantum harmonic oscillator on a circle. An expression for the effective coupling constant is obtained showing explicitly its dependence on the dimension of the box.Comment: 12 pages, Late

Optomechanical cooling of levitated spheres with doubly-resonant fields

Optomechanical cooling of levitated dielectric particles represents a promising new approach in the quest to cool small mechanical resonators towards their quantum ground state. We investigate two-mode cooling of levitated nanospheres in a self-trapping regime. We identify a rich structure of split sidebands (by a mechanism unrelated to usual strong-coupling effects) and strong cooling even when one mode is blue detuned. We show the best regimes occur when both optical fields cooperatively cool and trap the nanosphere, where cooling rates are over an order of magnitude faster compared to corresponding single-sideband cooling rates.Comment: 8 Pages, 7 figure

Generalized quantum field theory: perturbative computation and perspectives

We analyze some consequences of two possible interpretations of the action of the ladder operators emerging from generalized Heisenberg algebras in the framework of the second quantized formalism. Within the first interpretation we construct a quantum field theory that creates at any space-time point particles described by a q-deformed Heisenberg algebra and we compute the propagator and a specific first order scattering process. Concerning the second one, we draw attention to the possibility of constructing this theory where each state of a generalized Heisenberg algebra is interpreted as a particle with different mass.Comment: 19 page

Functionalizing self-assembled GaN quantum dot superlattices by Eu-implantation

Self-assembled GaN quantum dots (QDs) stacked in superlattices (SL) with AlN spacer layers were implanted with Europium ions to fluences of 1013, 1014, and 1015 cm−2. The damage level introduced in the QDs by the implantation stays well below that of thick GaN epilayers. For the lowest fluence, the structural properties remain unchanged after implantation and annealing while for higher fluences the implantation damage causes an expansion of the SL in the [0001] direction which increases with implantation fluence and is only partly reversed after thermal annealing at 1000 °C. Nevertheless, in all cases, the SL quality remains very good after implantation and annealing with Eu ions incorporated preferentially into near-substitutional cation sites. Eu3+ optical activation is achieved after annealing in all samples. In the sample implanted with the lowest fluence, the Eu3+ emission arises mainly from Eu incorporated inside the QDs while for the higher fluences only the emission from Eu inside the AlN-buffer, capping, and spacer layers is observed. © 2010 American Institute of PhysicsFCT-PTDC/CTM/100756/2008program PESSOA EGIDE/GRICESFCT-SFRH/BD/45774/2008FCT-SFRH/BD/44635/200

Development of geoprocessing applications for the Pantanal using automated compositions of web services.

This paper presents an approach to develop geo-processing applications for the Pantanal region using automated compositions of geographic Web Services. The procedure for the automatic construction of these compositions is based on rules of geo-data quality requirements which indicate the conditions for geo-data use by a geo-processing functionality. These rules can be defined to describe geospatial characteristics to select suitable geo-processing services for use in the Pantanal region. Therefore this approach produces more robust and reliable service compositions, generating better quality geo-data when compared with other composition approaches.Número especial

Desenvolvimento de aplicações em geoprocessamento usando composição automatizada de serviços geográfcos.

Este trabalho apresenta uma abordagem para construção de aplicações em geoprocessamento através da composição automatizada de Web Services geográfcos. O problema de composição é modelado como um problema de planejamento condicional onde, regras semânticas de requisitos de qualidade de geodados são utilizadas como uma indicação de condições de uso de um dado por uma funcionalidade de geoprocessamento. Esta abordagem permite a criação de composições de serviços mais robustas, confáveis e capazes de produzir geodados de melhor qualidade.Geopantanal 2010

Poliploidia em seringueira: III - Estudo comparativo entre clones diplóides e novos poliplóides putativos em condições de jardim clonal.

Foram avaliadas a produção de borracha e o vigor das plantas em clones putativos de Hevea brasiliensis (Fx 3864 pl e Fx 985 pl)

Plantas medicinais utilizadas na medicina etnoveterinária praticada na ilha do Marajó.

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