Unitary transformation approach for the trapped ion dynamics

We present a way of treating the problem of the interaction of a single trapped ion with laser beams based on successive aplications of unitary transformations onto the Hamiltonian. This allows the diagonalization of the Hamiltonian, by means of recursive relations, without performing the Lamb-Dicke approximation.Comment: 8 page

Quadratic Effective Action for QED in D=2,3 Dimensions

We calculate the effective action for Quantum Electrodynamics (QED) in D=2,3 dimensions at the quadratic approximation in the gauge fields. We analyse the analytic structure of the corresponding nonlocal boson propagators nonperturbatively in k/m. In two dimensions for any nonzero fermion mass, we end up with one massless pole for the gauge boson . We also calculate in D=2 the effective potential between two static charges separated by a distance L and find it to be a linearly increasing function of L in agreement with the bosonized theory (massive Sine-Gordon model). In three dimensions we find nonperturbatively in k/m one massive pole in the effective bosonic action leading to screening. Fitting the numerical results we derive a simple expression for the functional dependence of the boson mass upon the dimensionless parameter e^{2}/m .Comment: 10 pages, 2 figure

Relativistic Mean-Field Hadronic Models under Nuclear Matter Constraints

Relativistic mean-field (RMF) models have been widely used in the study of many hadronic frameworks because of several important aspects not always present in nonrelativistic models, such as intrinsic Lorentz covariance, automatic inclusion of spin, appropriate saturation mechanism for nuclear matter, causality and, therefore, no problems related to superluminal speed of sound. With the aim of identifying the models which best satisfy well known properties of nuclear matter, we have analyzed $263$ parameterizations of seven different types of RMF models under three different sets of constraints related to symmetric nuclear matter, pure neutron matter, symmetry energy, and its derivatives. One of these (SET1) is formed of the same constraints used in a recent work [M. Dutra et al., Phys. Rev. C 85, 035201 (2012)] in which we analyzed $240$ Skyrme parameterizations. The results pointed to $2$ models consistent with all constraints. By using another set of constraints, namely, SET2a, formed by the updated versions of the previous one, we found $4$ models approved simultaneously. Finally, in the third set, named SET2b, in which the values of the constraints are more restrictive, we found $3$ consistent models. Another interesting feature of our analysis is that the results change dramatically if we do not consider the constraint regarding the volume part of the isospin incompressibility ($K_{\tau,\rm v}$). In this case, we have $35$ approved models in SET2a and $30$ in SET2b.Comment: 63 pages, 3 figures and 9 tables. Version accepted for publication in PR

Estrutura de sistemas silvipastoris na região nordeste paraense.

Os sistemas silvipastoris (SSPs) são sistemas agroflorestais que associam, na mesma área de cultivo, espécies arbóreas, pastagens e animais. Utilizou-se um questionário para levantamento desses sistemas na região nordeste paraense. Uma análise desses SSPs indica as seguintes características: a) a área média ocupada com os sistemas silvipastoris nas fazendas apresentadas está em torno de 45 ha, ocupando cerca de 20 % da área total, em tipos climáticos Af, Am e Aw; b) em geral, os sistemas silvipastoris têm o componente arbóreo plantado, sendo constituído pelas espécies: Paricá (Schizolobium amazonicum Huber ex Ducke), Teca (Tectona grandis L. f.), Mogno (Swietenia macrophylla King), Mogno-africano (Khaya ivorensis A. Chev.) e Samaúma (Ceiba pentandra (L.) Gaertn.); c) a densidade estimada das árvores é considerada alta, em torno de 480 árvores/ha; d) em termos médios, o componente arbóreo apresenta idade de 7 anos, altura de 9 metros, estando, portanto, em estágios iniciais de desenvolvimento; e) o componente pastagem está, principalmente, representado pelas espécies: Quicuio-da-amazônia (Brachiaria humidicola Schweick.) e Braquiarão (Brachia-ria brizantha Stapf), com pastejo de bovinos ou ovinos. As principais limitações tecnológicas dos SSPs observadas em áreas de produtores e em experimentos realizados são: a) baixa persistência da pastagem no sub-bosque, decorrente da não adaptação às condições de baixa luminosidade, superpastejo e concorrência com invasoras; b) danos às árvores, provocados pelos animais em virtude do pastejo precoce do sistema ou uso de tipo de animal inadequado; c) diminuição da taxa de crescimento das árvores, em decorrência de interferências por competição do estrato herbáceo ou interferências alelopáticas promovidas pelo componente pastagem ou plantas invasoras.bitstream/item/29492/1/BPD64.pdfVersão eletrônica. 1ª impressão: 2009

Relativistic Mean-Field Models and Nuclear Matter Constraints

This work presents a preliminary study of 147 relativistic mean-field (RMF) hadronic models used in the literature, regarding their behavior in the nuclear matter regime. We analyze here different kinds of such models, namely: (i) linear models, (ii) nonlinear \sigma^3+\sigma^4 models, (iii) \sigma^3+\sigma^4+\omega^4 models, (iv) models containing mixing terms in the fields \sigma and \omega, (v) density dependent models, and (vi) point-coupling ones. In the finite range models, the attractive (repulsive) interaction is described in the Lagrangian density by the \sigma (\omega) field. The isospin dependence of the interaction is modeled by the \rho meson field. We submit these sets of RMF models to eleven macroscopic (experimental and empirical) constraints, used in a recent study in which 240 Skyrme parametrizations were analyzed. Such constraints cover a wide range of properties related to symmetric nuclear matter (SNM), pure neutron matter (PNM), and both SNM and PNM.Comment: 3 Pages, submitted for proceedings of XXXV Reuni\~ao de Trabalho sobre F\'isica Nuclear no Brasil 201

Sistemas silvipastoris do Nordeste paraense.

Publicado também como folder (FD 00711).bitstream/item/28248/1/ComTec120.pdfDisponível também on-line

Levantamento de sistemas silvipastoris no estado do Pará, Brasil.

Editores: Luis Lamela López, Jesús Suárez Hernández, Nayda Armengol López, Alicia Ojeda González

Cosmological scenarios from multiquintessence

In this work we derive and analyse cosmological scenarios coming from multi-component scalar field models. We consider a direct sum of a sine-Gordon with a Z2 model, and also a combination of those with a BNRT model. Moreover, we work with a modified version of the BNRT model, which breaks the Z2 x Z2 symmetry of the original BNRT potential, coupled with the sine-Gordon and with the standard Z2 models. We show that our approach can be straightforwardly elevated to $N$ fields. All the computations are made analytically and some parameters restriction is put forward in order to get in touch with complete and realistic cosmological scenarios