Dynamical Casimir effect with cylindrical waveguides

I consider the quantum electromagnetic field in a coaxial cylindrical waveguide, such that the outer cylindrical surface has a time-dependent radius. The field propagates parallel to the axis, inside the annular region between the two cylindrical surfaces. When the mechanical frequency and the thickness of the annular region are small enough, only Transverse Electromagnetic (TEM) photons may be generated by the dynamical Casimir effect. The photon emission rate is calculated in this regime, and compared with the case of parallel plates in the limit of very short distances between the two cylindrical surfaces. The proximity force approximation holds for the transition matrix elements in this limit, but the emission rate scales quadratically with the mechanical frequency, as opposed to the cubic dependence for parallel plates.Comment: 6 page

Existence, nonexistence and uniqueness for Lane-Emden type fully nonlinear systems

We study existence, nonexistence, and uniqueness of positive radial solutions for a class of nonlinear systems driven by Pucci extremal operators under a Lane-Emden coupling configuration. Our results are based on the analysis of the associated quadratic dynamical system and energy methods. For both regular and exterior domain radial solutions we obtain new regions of existence and nonexistence. Besides, we show an exclusion principle for regular solutions, either in RN or in a ball, by exploiting the uniqueness of trajectories produced by the flow. In particular, for the standard Lane-Emden system involving the Laplacian operator, we prove that the critical hyperbola of regular radial positive solutions is also the threshold for existence and nonexistence of radial exterior domain solutions with Neumann boundary condition. As a byproduct, singular solutions with fast decay at infinity are also found

Quantum radiation in a plane cavity with moving mirrors

We consider the electromagnetic vacuum field inside a perfect plane cavity with moving mirrors, in the nonrelativistic approximation. We show that low frequency photons are generated in pairs that satisfy simple properties associated to the plane geometry. We calculate the photon generation rates for each polarization as functions of the mechanical frequency by two independent methods: on one hand from the analysis of the boundary conditions for moving mirrors and with the aid of Green functions; and on the other hand by an effective Hamiltonian approach. The angular and frequency spectra are discrete, and emission rates for each allowed angular direction are obtained. We discuss the dependence of the generation rates on the cavity length and show that the effect is enhanced for short cavity lengths. We also compute the dissipative force on the moving mirrors and show that it is related to the total radiated energy as predicted by energy conservation.Comment: 17 pages, 1 figure, published in Physical Review

Dust Emission from Active Galactic Nuclei

Unified schemes of active galactic nuclei (AGN) require an obscuring dusty torus around the central source, giving rise to Seyfert 1 line spectrum for pole-on viewing and Seyfert 2 characteristics in edge-on sources. Although the observed IR is in broad agreement with this scheme, the behavior of the 10 micron silicate feature and the width of the far-IR emission peak remained serious problems in all previous modeling efforts. We show that these problems find a natural explanation if the dust is contained in about 5-10 clouds along radial rays through the torus. The spectral energy distributions (SED) of both type 1 and type 2 sources are properly reproduced from different viewpoints of the same object if the visual optical depth of each cloud is larger than about 60 and the clouds' mean free path increases roughly in proportion to radial distance.Comment: 11 pages, submitted to ApJ Letter

EFEITO DA ADUBAÇÃO COM LODO DE ESGOTO NAS CARACTERÍSTICAS QUÍMICAS DO SOLO, DESENVOLVIMENTO VEGETATIVO, PRODUTIVIDADE E QUALIDADE DE FRUTOS DE ABACAXIZEIRO cv. VITÓRIA VITÓRIA

RESUMO O lodo de Estação de Tratamento de Esgoto (ETE) é um resíduo com elevado potencial agronômico, com quantidades significativas de macro e micronutrientes, distribuídos de forma equilibrada e com possibilidade de aplicação na agricultura. O objetivo geral deste trabalho foi avaliar a influencia do lodo de ETE sobre as características químicas do solo, a disponibilidade de nutrientes para o abacaxizeiro, o crescimento, desenvolvimento vegetativo e características póscolheita do fruto do abacaxizeiro cv. Vitória, adubados com diferentes doses de lodo de ETE higienizados com cal virgem e também com um fertilizante químico mineral e um orgânico. Devido à baixa disponibilidade de fósforo e potássio no lodo, foi feita a adição desses elementos em todos os tratamentos. Foram avaliados o comprimento e a largura da folha D do abacaxizeiro e o peso da massa da matéria úmida e seca da folha D antes da indução floral para análise do desenvolvimento vegetativo. Foi realizada análise foliar dos nutrientes presentes na folha D, peso dos frutos com e sem coroa, comprimento dos frutos e diâmetros dos frutos e dos talos. Os teores de sólidos solúveis totais e a acidez titulável. Foram avaliadas as características químicas do solo após aplicação dos tratamentos, as quais foram comparadas com outras formas de fertilização no solo, correlacionando-se os teores dos elementos no solo e na planta. A elevação nas doses de lodo de ETE no solo provocaram elevação do pH, redução da acidez potencial, elevação do teor de matéria orgânica, fósforo e do boro no solo. Foram observadas relações funcionais entre as doses de lodo e os teores de enxofre, ferro e boro na folha e correlação entre a elevação do pH e a absorção do fósforo, ferro, zinco e manganês no tecido foliar; elevação nos teores de enxofre e boro em função da adição de matéria orgânica. Foi possível estabelecer um modelo de regressão quadrática para os fatores de peso do fruto com coroa e sem coroa e para a produtividade, sugerindo que o lodo de ETE é uma fonte de nutrientes para a cultura. Não houve contaminação biológica dos frutos de abacaxi ´Vitória` fertilizado do com lodo de ETE após o experimento. Palavras-chave: Abacaxi 'Vitória'; lodo de esgoto; Biossólido; Nutrição mineral de plantas

Inertial forces in the Casimir effect with two moving plates

We combine linear response theory and dimensional regularization in order to derive the dynamical Casimir force in the low frequency regime. We consider two parallel plates moving along the normal direction in $D-$dimensional space. We assume the free-space values for the mass of each plate to be known, and obtain finite, separation-dependent mass corrections resulting from the combined effect of the two plates. The global mass correction is proportional to the static Casimir energy, in agreement with Einstein's law of equivalence between mass and energy for stressed rigid bodies.Comment: 9 pages, 1 figure; title and abstract changed; to appear in Physical Review