Physical properties of the Schur complement of local covariance matrices

General properties of global covariance matrices representing bipartite Gaussian states can be decomposed into properties of local covariance matrices and their Schur complements. We demonstrate that given a bipartite Gaussian state $\rho_{12}$ described by a $4\times 4$ covariance matrix \textbf{V}, the Schur complement of a local covariance submatrix $\textbf{V}_1$ of it can be interpreted as a new covariance matrix representing a Gaussian operator of party 1 conditioned to local parity measurements on party 2. The connection with a partial parity measurement over a bipartite quantum state and the determination of the reduced Wigner function is given and an operational process of parity measurement is developed. Generalization of this procedure to a $n$-partite Gaussian state is given and it is demonstrated that the $n-1$ system state conditioned to a partial parity projection is given by a covariance matrix such as its $2 \times 2$ block elements are Schur complements of special local matrices.Comment: 10 pages. Replaced with final published versio

Alternate islands of multiple isochronous chains in wave-particle interactions

We analyze the dynamics of a relativistic particle moving in a uniform magnetic field and perturbed by a standing electrostatic wave. We show that a pulsed wave produces an infinite number of perturbative terms with the same winding number, which may generate islands in the same region of phase space. As a consequence, the number of isochronous island chains varies as a function of the wave parameters. We observe that in all the resonances, the number of chains is related to the amplitude of the various resonant terms. We determine analytically the position of the periodic points and the number of island chains as a function of the wave number and wave period. Such information is very important when one is concerned with regular particle acceleration, since it is necessary to adjust the initial conditions of the particle to obtain the maximum acceleration.Comment: Submitte

Proposta metodológica para avaliação da efetividade das políticas sociais para agricultores familiares do Estado de Goiás.

O objetivo principal desse artigo é realizar uma revisão bibliográfica e uma proposta metodológica para avaliar as efetividades sociais das políticas públicas para os agricultores familiares do estado de Goiás. Os programas escolhidos pelas suas representatividades sociais e econômicas para o campo e especificamente para a agricultura familiar, sujeito deste trabalho, são o Programa Nacional da Alimentação Escolar (PNAE), o Programas de Aquisição de Alimentos (PAA) da Agricultura Familiar. Também será abordado o Programa Bolsa Família, que não se trata da temática da segurança alimentar, mas que é um programa social de grande inserção no meio rural, especificamente para os agricultores familiares, e com a hipótese que tem efeitos significativos em elementos de segurança alimentar dos agricultores familiares do território em questão

Scaling in a continuous time model for biological aging

In this paper we consider a generalization to the asexual version of the Penna model for biological aging, where we take a continuous time limit. The genotype associated to each individual is an interval of real numbers over which Dirac $\delta$--functions are defined, representing genetically programmed diseases to be switched on at defined ages of the individual life. We discuss two different continuous limits for the evolution equation and two different mutation protocols, to be implemented during reproduction. Exact stationary solutions are obtained and scaling properties are discussed.Comment: 10 pages, 6 figure

Instantaneous cell migration velocity may be ill-defined

Cell crawling is critical to biological development, homeostasis and disease. In many cases, cell trajectories are quasi-random-walk. In vitro assays on flat surfaces often described such quasi-random-walk cell trajectories as approximations to a solution of a Langevin process. However, experiments show quasi-diffusive behavior at small timescales, indicating that instantaneous velocity and velocity autocorrelations are not well-defined. We propose to characterize mean-squared cell displacement using a modified F\"urth equation with three temporal and spatial regimes: short- and long-time/range diffusion and intermediate time/range ballistic motion. This analysis collapses mean-squared displacements of previously published experimental data onto a single-parameter family of curves, allowing direct comparison between movement in different cell types, and between experiments and numerical simulations. Our method also show that robust cell-motility quantification requires an experiment with a maximum interval between images of a few percent of the cell-motion persistence time or less, and a duration of a few orders-of-magnitude longer than the cell-motion persistence time or more.Comment: 5 pages, plus Supplemental materia

Decoherence of Semiclassical Wigner Functions

The Lindblad equation governs general markovian evolution of the density operator in an open quantum system. An expression for the rate of change of the Wigner function as a sum of integrals is one of the forms of the Weyl representation for this equation. The semiclassical description of the Wigner function in terms of chords, each with its classically defined amplitude and phase, is thus inserted in the integrals, which leads to an explicit differential equation for the Wigner function. All the Lindblad operators are assumed to be represented by smooth phase space functions corresponding to classical variables. In the case that these are real, representing hermitian operators, the semiclassical Lindblad equation can be integrated. There results a simple extension of the unitary evolution of the semiclassical Wigner function, which does not affect the phase of each chord contribution, while dampening its amplitude. This decreases exponentially, as governed by the time integral of the square difference of the Lindblad functions along the classical trajectories of both tips of each chord. The decay of the amplitudes is shown to imply diffusion in energy for initial states that are nearly pure. Projecting the Wigner function onto an orthogonal position or momentum basis, the dampening of long chords emerges as the exponential decay of off-diagonal elements of the density matrix.Comment: 23 pg, 2 fi

Qualidade de milho verde cultivado em sistemas de produção orgânico e convencional.

Avaliaram-se as características agronômicas e físico-químicas de milho verde cultivado em sistemas de produção orgânico e convencional. Utilizou-se o delineamento experimental inteiramente casualizado, em esquema fatorial 4 x 2, sendo quatro cultivares (AG 1051, BR 106, SWB 551 e VIVI), nos sistemas orgânico e convencional, com três repetições. As características agronômicas analisadas foram peso das espigas com palhas (PP) e despalhadas (PD), peso dos grãos (PG), peso do sabugo (PS), peso da palha (P), comprimento da espiga com palha (CE), percentual relativo de grãos (PRG), percentual relativo de palha (PRP) e percentual relativo de sabugo (PRS). Foram, ainda, analisados o teor de umidade e as características físico-químicas (pH, acidez titulável e sólidos solúveis totais) dos grãos verdes. As espigas produzidas no sistema convencional apresentaram PP, PD e PG superiores aos das espigas produzidas em sistema orgânico, para a cultivar AG 1051. O mesmo comportamento foi observado para o CE da cultivar SWB 551 e o PG da cultivar BR 106. No sistema convencional, a cultivar AG 1051 destacou-se nas características agronômicas avaliadas. Os valores médios de pH, diferentemente da acidez, foram superiores no cultivo orgânico. A cultivar SWB 551 apresentou maior percentual de sólidos solúveis entre as cultivares. Portanto, o sistema de produção influencia as principais características de qualidade do milho verde