Luttinger liquid superlattices: realization of gapless insulating phases

We investigate Luttinger Liquid superlattices, a periodic structure composed of two kinds of one-dimensional systems of interacting electrons. We calculate several properties of the low-energy sector: the effective charge and spin velocities, the compressibility, various correlation functions, the Landauer conductance and the Drude weight. The low-energy properties are subsumed into effective parameters, much like homogeneous one-dimensional systems. A generic result is the weighted average nature of these parameters, in proportion to the spatial extent of the underlying subunits, pointing to the possibility of ``engineered'' structures. As a specific realization, we consider a one-dimensional Hubbard superlattice, which consists of a periodic arrangement of two long Hubbard chains with different coupling constants and different hopping amplitudes. This system exhibits a rich phase diagram with several phases, both metallic and insulating. We have found that gapless insulating phases are present over a wide range of parameters.Comment: 16 pages, 15 figures, RevTeX

Lorentz-violating nonminimal coupling contributions in mesonic hydrogen atoms and generation of photon higher-order derivative terms

We have studied the contributions of Lorentz-violating CPT-odd and CPT-even nonminimal couplings to the energy spectrum of the mesonic hydrogen and the higher-order radiative corrections to the effective action of the photon sector of a Lorentz-violating version of the scalar electrodynamics. By considering the complex scalar field describes charged mesons (pion or kaon), the non-relativistic limit of the model allows to attain upper-bounds by analyzing its contribution to the mesonic hydrogen energy. By using the experimental data for the $1S$ strong correction shift and the pure QED transitions $4P \rightarrow 3P$, the best upper-bound for the CPT-odd coupling is $<10^{-12}\text{eV}^{-1}$ and for the CPT-even one is $<10^{-16}\text{eV}^{-2}$. Besides, the CPT-odd radiative correction to the photon action is a dimension-5 operator which looks like a higher-order Carroll-Field-Jackiw term. The CPT-even radiative contribution to the photon effective action is a dimension-6 operator which would be a higher-order derivative version of the minimal CPT-even term of the standard model extension

Coherent State Path Integrals in the Weyl Representation

We construct a representation of the coherent state path integral using the Weyl symbol of the Hamiltonian operator. This representation is very different from the usual path integral forms suggested by Klauder and Skagerstan in \cite{Klau85}, which involve the normal or the antinormal ordering of the Hamiltonian. These different representations, although equivalent quantum mechanically, lead to different semiclassical limits. We show that the semiclassical limit of the coherent state propagator in Weyl representation is involves classical trajectories that are independent on the coherent states width. This propagator is also free from the phase corrections found in \cite{Bar01} for the two Klauder forms and provides an explicit connection between the Wigner and the Husimi representations of the evolution operator.Comment: 23 page

Avaliação de métodos de inoculação de Phytophthora palmivora em mudas de pupunheira.

Resumo

Perdas de grãos na cultura do milho: pré-colheita, colheita, transporte e armazenamento.

Perdas na pre-colheita; Perdas na colheita; Perdas na pos-colheita; Principais pragas dos graos armazenados; Conseguencias do ataque de insetos; Formas de armazenamento e recomendacoes.bitstream/item/37533/1/circ-24.pd

Número de aplicações de metalaxyl + mancozeb para o controle do míldio-do-meloeiro.

Este trabalho teve o objetivo de determinar o numero de aplicacoes do fungicida metalaxyl + mancozeb, suficiente para o controle do mildio.bitstream/CNPAT-2010/8611/1/Ct-092.pd

Optimization of tree arrangements in silvopastoral systems in the Pampa biome.

Resumo

A nearly cylindrically symmetric source in the Brans-Dicke gravity as the generator of the rotational curves of the galaxies

Observation shows that the velocities of stars grow by approximately 2 to 3 orders of magnitude when the distances from the centers of the galaxies are in the range of $0.5$ kpc to $82.3$ kpc, before they begin to tend to a constant value. Up to know, the reason for this behavior is still a matter for debate. In this work, we propose a model which adequately describes this unusual behavior using a (nearly) cylindrical symmetrical solution in the framework of a scalar-tensor-like (the Brans-Dicke model) theory of gravity.Comment: 24 pages, 4 figures, accepted for publication in Eur. Phys. J.