Periodic orbit bifurcations and scattering time delay fluctuations

We study fluctuations of the Wigner time delay for open (scattering) systems which exhibit mixed dynamics in the classical limit. It is shown that in the semiclassical limit the time delay fluctuations have a distribution that differs markedly from those which describe fully chaotic (or strongly disordered) systems: their moments have a power law dependence on a semiclassical parameter, with exponents that are rational fractions. These exponents are obtained from bifurcating periodic orbits trapped in the system. They are universal in situations where sufficiently long orbits contribute. We illustrate the influence of bifurcations on the time delay numerically using an open quantum map.Comment: 9 pages, 3 figures, contribution to QMC200

Sôbre o plâncton da enseada do Mar Virado e os métodos de coletas

This paper presents the results of a series of investigations made on plankton samples (Table I) taken from October to December 1960 in the "Enseada do Mar Virado" (State of São Paulo, Brazil) (Fig. 1). The samples were studied under their general aspect. Four stations were occupied along a line at four different occasions. At each, samples were taken by means of vertical hauls with two similar plankton nets 25 cm wide at the mouth, one called "phytoplankton mesh" (1 mm wide apertures) and the other "zooplankton mesh" (3 mm wide apertures). First, a study on the quantitative composition of the plankton was carried out. A relationship was established between the amount of plankton and the oceanographic station (Fig. 2), date of hauls, water masses and other environmental conditions. The following results were obtained: the amount of plankton seems to be greater in Station I than in Station II, III and IV, which means that the amount of plankton was greater in coastal than in shelf waters. Phytoplankton on the contrary, was always more abundant in shelf waters (Figs. 3, 4). A comparative analysis was made of the samples taken with phytoplankton and zooplankton meshes. It was verified that the phytoplankton mesh really selects only small animals and that larger organisms are not retained by any of them (Figs. 5-12). Finally a study on the relationship between the planktonic animals (Table II) and the habitat, especially in what concerns the zooplankton, revealed that the latter is essencially neritic.O presente trabalho é um estudo do plancton da enseada do Mar Virado (Fig. 1) sob seus aspectos mais gerais. O plancton foi coletado quatro vezes em quatro estações dispostas em linha reta, nos meses de outubro, novembro e dezembro de 1960 (Tabela I). Foram feitas coletas verticais com duas redes de fito e zooplâncton, ambas das mesmas dimensões. Primeiramente, fizemos o estudo da composição quantitativa do plâncton. Relacionamos a quantidade de plâncton com as estações oceanográficas (Fig. 2), datas de coleta, massas de água e outras condições do meio ambiente. Obtivemos os seguintes resultados: a quantidade de plancton parece ser maior na Estação I e diminuir nas II, III e IV, isto é, maior em água costeira e menor em água de plataforma. Para o fitoplâncton obtivemos um resultado oposto, isto é, foi sempre mais abundante na presença de água de plataforma (Figs. 3-4). Em seguida, fizemos uma análise comparativa das amostras coletadas com rede de fitoplâncton e de zooplâncton. Baseados nesta análise, verificamos que a rede de fitoplâncton seleciona positivamente apenas os animais de pequeno porte, e que os organismos maiores não sofrem seleção nem pela rede de fitoplâncton nem pela de zooplâncton (Figs. 5-12). Finalmente, fizemos um estudo das relações dos organismos planctônicos (Tabela II) com o meio ambiente, especialmente no que diz respeito ao zooplâncton e concluimos que este é essencialmente nerítico

Chaetognatha encontrados em águas brasileiras

Four species of Sagitta found in Brazilian waters are redescribed in this paper. Sagitta friderici - Numerous sensory hairs and areas are regularly distributed over the epidermis. Clearly defined collarette. Formula of the buccal armature:. Caudal to total length ratio: 25.8-29.1. Seminal vesicles almost reach posterior fins and are in contact with caudal fin; with anterior spherical swelling. Elongated ovary with eggs arranged in several rows. Sagitta hispida - Head very wide in relation to body and large collarette. Formula of buccal armature: . Caudal to total length ratio: 25.0-28.5. Seminal vesicles touch posterior fins and are separated from caudal fin. Long ovary with several rows of eggs. Sagitta minima - Has a typical body shape, small head, body widened posteriorly, tail segment thin. Collarette absent. Formula of buccal armature:. As the specimens grow, the caudal to total length ratio gradually shifts from 22.7-16.6. Seminal vesicles are separated from posterior fins and touch caudal fin. Ovary short with few eggs. Sagitta tenuis - A small species, similar to Sagitta friderici but smaller. Similarly to S. friderici it has sensory hairs and areas on the body surface. Collarette small. Formula of buccal armature:. Caudal to total length ratio: 25.0-31.8. Seminal vesicles almost touch posterior fins and touch caudal fin: anterior portion of vesicles swollen. Ovary short with few large eggs, this being its principal differential character from S. friderici. The variation indicated in the formulae of the buccal armature and of caudal to total length ratio refer to specimens of different sizes.Este trabalho contém a descrição de quatro espécies de Sagitta coletadas em águas brasileiras. Sagitta friderici - A epiderme apresenta numerosas manchas e cerdas sensoriais distribuídas regularmente. Colarinho nítido. Fórmula da armadura bucal:. Comprimento da cauda em relação ao comprimento total: 25,8 a 29,1%. A nadadeira posterior quase toca a vesícula seminal e a caudal inicia-se no fim desta; a vesícula seminal possui uma saliência esférica anterior. O ovário é alongado e possui várias fileiras de óvulos. Sagitta hispida - Possui cabeça muito larga em relação ao tronco e colarinho grande. Fórmula da armadura bucal:. Comprimento da cauda em relação ao comprimento total: 25,0 a 28,5%. A nadadeira posterior toca a vesícula seminal e a caudal é separada desta por um pequeno espaço. O ovário é alongado e possui várias fileiras de óvulos. Sagitta minima - Caracterizada pela forma do corpo: cabeça pequena, corpo alargado posteriormente e a cauda fina. Colarinho ausente. Fórmula da armadura bucal: . O comprimento da cauda em relação ao comprimento total varia, com o crescimento, de 22,7 e 16,6%. A vesícula seminal é separada da nadadeira posterior mas toca a nadadeira caudal. O ovário é curto e possui poucos óvulos. Sagitta tenuis - Espécie muito pequena, semelhante à Sagitta friderici, cujos indivíduos são maiores. Tem, como Sagitta friderici, manchas e cerdas sensoriais na superfície do corpo. O colarinho é pequeno. Fórmula da armadura bucal:. O comprimento da cauda em relação ao comprimento total: 25,0 a 31,8%. A nadadeira posterior quase toca a vesícula seminal e a caudal inicia-se no fim desta. A vesícula seminal possui uma saliência esférica anterior. O ovário é curto e tem poucos e grandes óvulos, principal caráter que a distingue de Sagitta friderici. A variação da armadura bucal e do comprimento da cauda em relação ao comprimento total é relativa aos indivíduos de vários tamanhos

Distribuição dos Chaetognatha no atlântico sul ocidental

Estuda-se neste trabalho, a distribuição geográfica dos Chaetognatha no Atlântico Sul Ocidental relacionando as dez espécies encontradas com as diferentes massas de água. Foram feitas estações em águas costeira, da plataforma e tropical. Finalmente, foi relacionada a presença dos Chaetognatha e das medusas com as diferentes massas de água.This paper refers to a geographic study of the distribution of Chaetognatha in the Western South Atlantic and the ten different species are discussed in relation to different water masses. Samples were taken in coastal, shelf and tropical waters. Finally a correlation of the medusan, chaetognath and water mass distribution was tentatively made

Universal quantum signature of mixed dynamics in antidot lattices

We investigate phase coherent ballistic transport through antidot lattices in the generic case where the classical phase space has both regular and chaotic components. It is shown that the conductivity fluctuations have a non-Gaussian distribution, and that their moments have a power-law dependence on a semiclassical parameter, with fractional exponents. These exponents are obtained from bifurcating periodic orbits in the semiclassical approximation. They are universal in situations where sufficiently long orbits contribute.Comment: 7 page

Superscars in the LiNC=LiCN isomerization reaction

We demonstrate the existence of superscarring in the LiNC=LiCN isomerization reaction described by a realistic potential interaction in the range of readily attainable experimental energies. This phenomenon arises as the effect of two periodic orbits appearing "out of the blue"in a saddle--node bifurcation taking place in the dynamics of the system. Potential practical consequences of this superlocalization in the corresponding wave functions are also considered.Comment: 6 pages, 5 figures. to appear in EP

Decoherence-free evolution of time-dependent superposition states of two-level systems and thermal effects

In this paper we detail some results advanced in a recent letter [Prado et al., Phys. Rev. Lett. 102 073008 (2009)] showing how to engineer reservoirs for two-level systems at absolute zero by means of a time-dependent master equation leading to a nonstationary superposition equilibrium state. We also present a general recipe showing how to build nonadiabatic coherent evolutions of a fermionic system interacting with a bosonic mode and investigate the influence of thermal reservoirs at finite temperature on the fidelity of the protected superposition state. Our analytical results are supported by numerical analysis of the full Hamiltonian model.Comment: 7 pages, 4 figure

Seleção de populações segregantes de feijoeiro-comum carioca com altos teores de ferro e zinco.

O objetivo deste trabalho foi obter genitores e populações segregantes de feijoeiro-comum com potencial para altos teores de ferro e zinco.CONAF

Optimal transfers from Moon to L2L_2 halo orbit of the Earth-Moon system

In this paper, we seek optimal solutions for a transfer from a parking orbit around the Moon to a halo orbit around $L_2$ of the Earth-Moon system, by applying a single maneuver and exploiting the stable invariant manifold of the hyperbolic parking solution at arrival. For that, we propose an optimization problem considering as variables both the orbital characteristics of a parking solution around the Moon, (namely, its Keplerian elements) and the characteristics of a transfer trajectory guided by the stable manifold of the arrival Halo orbit. The problem is solved by a nonlinear programming method (NLP), aiming to minimize the cost of $\Delta V$ to perform a single maneuver transfer, within the framework of the Earth-Moon system of the circular restricted three-body problem. Results with low $\Delta V$ and suitable time of flight show the feasibility of this kind of transfer for a Cubesat

Numerical investigations of the orbital dynamics around a synchronous binary system of asteroids

In this article, equilibrium points and families of periodic orbits in the vicinity of the collinear equilibrium points of a binary asteroid system are investigated with respect to the angular velocity of the secondary body, the mass ratio of the system and the size of the secondary. We assume that the gravitational fields of the bodies are modeled assuming the primary as a mass point and the secondary as a rotating mass dipole. This model allows to compute families of planar and halo periodic orbits that emanate from the equilibrium points $L_1$ and $L_2$. The stability and bifurcations of these families are analyzed and the results are compared with the results obtained with the Restricted Three-Body Problem (RTBP). The results provide an overview of the dynamical behavior in the vicinity of a binary asteroid system