Enhancement of particle trapping in the wave-particle interaction

The saturated dynamics of a Single-Pass Free Electron Laser is considered within a simplified mean-field approach. A method is proposed to increase the size of the macro-particle, which is responsible for the oscillations of the intensity of the wave. This approach is based on the reconstruction of invariant tori of the dynamics of test particles. To this aim a dedicated control term is derived, the latter acting as a small apt perturbation of the system dynamics. Implications of these findings are discussed in relation to the optimization of the laser source

A maximum entropy principle explains quasi-stationary states in systems with long-range interactions: the example of the Hamiltonian Mean Field model

A generic feature of systems with long-range interactions is the presence of {\it quasi-stationary} states with non-Gaussian single particle velocity distributions. For the case of the Hamiltonian Mean Field (HMF) model, we demonstrate that a maximum entropy principle applied to the associated Vlasov equation explains known features of such states for a wide range of initial conditions. We are able to reproduce velocity distribution functions with an analytical expression which is derived from the theory with no adjustable parameters. A normal diffusion of angles is detected and a new dynamical effect, two oscillating clusters surrounded by a halo, is also found and theoretically justified.Comment: 4 pages, 3 figs, submitted to Phys. Rev. Let

An update on χc\chi_c Decays: Perturbative QCD versus Data

We present a global fit of current available experimental results on $\chi_c$ decays within next-to-leading-order perturbative QCD. The quality and reduced errors of recent data improve the agreement between theory and experiment.Comment: 10 pages, Late

On the non-Boltzmannian nature of quasi-stationary states in long-range interacting systems

We discuss the non-Boltzmannian nature of quasi-stationary states in the Hamiltonian Mean Field (HMF) model, a paradigmatic model for long-range interacting classical many-body systems. We present a theorem excluding the Boltzmann-Gibbs exponential weight in Gibbs $\Gamma$-space of microscopic configurations, and comment a paper recently published by Baldovin and Orlandini (2006). On the basis of the points here discussed, the ongoing debate on the possible application, within appropriate limits, of the generalized $q$-statistics to long-range Hamiltonian systems remains open.Comment: 8 pages, 4 figures. New version accepted for publication in Physica

Out-of-equilibrium tricritical point in a system with long-range interactions

Systems with long-range interactions display a short-time relaxation towards Quasi Stationary States (QSSs) whose lifetime increases with system size. With reference to the Hamiltonian Mean Field (HMF) model, we here show that a maximum entropy principle, based on Lynden-Bell's pioneering idea of "violent relaxation", predicts the presence of out-of-equilibrium phase transitions separating the relaxation towards homogeneous (zero magnetization) or inhomogeneous (non zero magnetization) QSSs. When varying the initial condition within a family of "water-bags" with different initial magnetization and energy, first and second order phase transition lines are found that merge at an out--of--equilibrium tricritical point. Metastability is theoretically predicted and numerically checked around the first-order phase transition line.Comment: Physical Review Letters (2007

Enhancement of particle trapping in the Free Electron Laser

International audienceThe saturated dynamics of a Single Pass Free Electron Laser is here considered within a simplified mean field approach. A method is proposed to increase the size of the macro-particle. This approach is based on the reconstruction of invariant tori of the dynamics of test particles. To this aim a dedicated control term is derived, the latter acting as a small apt perturbation of the system dynamics. Implications of these findings are discussed in relation to the optimization of the laser source

Exploring the thermodynamic limit of Hamiltonian models: convergence to the Vlasov equation

We here discuss the emergence of Quasi Stationary States (QSS), a universal feature of systems with long-range interactions. With reference to the Hamiltonian Mean Field (HMF) model, numerical simulations are performed based on both the original $N$-body setting and the continuum Vlasov model which is supposed to hold in the thermodynamic limit. A detailed comparison unambiguously demonstrates that the Vlasov-wave system provides the correct framework to address the study of QSS. Further, analytical calculations based on Lynden-Bell's theory of violent relaxation are shown to result in accurate predictions. Finally, in specific regions of parameters space, Vlasov numerical solutions are shown to be affected by small scale fluctuations, a finding that points to the need for novel schemes able to account for particles correlations.Comment: 5 pages, 3 figure

Contrôler l'interaction onde-particules

International audienceNous nous intéressons à la dynamique saturé du Laser à Electrons Libres Simple Passage, à travers une approche champ moyen. Nous proposons une méthode afin d'accroître la taille de la macro-particule. Celle-ci repose sur la reconstruction de tores invariants de la dynamique de particules-test. A cette fin, un terme de contrôle - qui agit comme une faible perturbation du système - est calculé. Les possibles conséquences de cette stratégie vis-à-vis de l'optimisation du laser sont discutées

A closer look at the indications of q-generalized Central Limit Theorem behavior in quasi-stationary states of the HMF model

We give a closer look at the Central Limit Theorem (CLT) behavior in quasi-stationary states of the Hamiltonian Mean Field model, a paradigmatic one for long-range-interacting classical many-body systems. We present new calculations which show that, following their time evolution, we can observe and classify three kinds of long-standing quasi-stationary states (QSS) with different correlations. The frequency of occurrence of each class depends on the size of the system. The different microsocopic nature of the QSS leads to different dynamical correlations and therefore to different results for the observed CLT behavior.Comment: 11 pages, 8 figures. Text and figures added, Physica A in pres

Reproductive biology of Boana pulchella and Boana punctata (Anura: Hylidae) in sympatric populations of temperate wetlands

Boana pulchella habita principalmente climas templados y B. punctata principalmente climas tropicales, lo que permitiría suponer la presencia de estrategias reproductivas diferentes, aún en la región en la que sus poblaciones son simpátricas. En el presente estudio se analizaron y compararon los ciclos reproductivos, parámetros reproductivos y desarrollo de cuerpos grasos (CG) de Boana pulchella y B. punctata en humedales templados del río Paraná Medio. Boana pulchella presentó óvulos maduros de marzo a diciembre. En machos no hubo variación del volumen testicular a lo largo del año y el mayor desarrollo de CG de los machos se observó en invierno. Esta especie presentó un patrón reproductivo continuo. La vitelogénesis de B. punctata se inició en enero, alcanzando el mayor desarrollo ovárico en febrero (verano) y decreciendo hacia mayo (otoño). Los machos presentaron crecimiento testicular en verano, decreciendo hacia otoño y los CG presentaron su máximo desarrollo en enero para ambos sexos. Esta especie mostró un patrón reproductivo continuo. Ambas especies presentaron dimorfismo sexual con hembras que poseen una relación proporcional entre la talla y la inversión reproductiva. Boana pulchella presentó un mayor esfuerzo reproductivo (ER = 20,48 ± 12,9) y factor de tamaño ovárico (FTO = 25,73) que B. punctata (ER = 10,06 ± 4,45; FTO = 8,99). También se encontraron diferencias interespecíficas en la masa ovárica, complemento ovárico y volúmen testicular, siendo estas variables proporcionalmente mayores en B. pulchella. Las diferencias observadas en las poblaciones simpátricas podrían relacionarse con el desarrollo de estrategias reproductivas bajo diferentes presiones evolutivasBoana pulchella mainly inhabits temperate climates while B. punctata mainly inhabits tropical climates, which would allow assuming the presence of different reproductive strategies, even in the region in which their populations are sympatric. In the present study, we analyzed and compared the reproductive cycles, reproductive parameters, and fat bodies development of Boana pulchella and B. punctata inhabiting in sympatry in temperate wetlands of the Middle Paraná River. Boana pulchella presented mature ovaries from March to December. There was no seasonal variation in testicular size of males, and their fat bodies development was greater during winter. This species exhibited a continuous breeding pattern. The vitellogenesis of B. punctata began in January (summer), reaching higher ovarian development in February (summer) and decreasing to May (autumn). Testicles of males grew in summer and decline in autumn. Fat bodies presented their developmental peak in January for both sexes. This species exhibited a prolonged breeding season. Both species showed sexual dimorphism with larger females having a greater inversion in reproduction. Boana pulchella showed greater reproductive effort (RE = 20.48 ± 12.9) and ovarian size factor (OSF = 25.73) than B. punctata (RE = 10.06 ± 4.45; OSF = 8.99). We also found interspecific differences in ovarian mass, ovarian complement, and testicular volume, these variables being proportionally greater in B. pulchella. Observed differences in sympatric populations could reside in the development of reproductive strategies under different evolutionary pressures.Fil: Antoniazzi, Carolina Elizabet. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina. Universidad Católica de Santa Fe; ArgentinaFil: López, Javier Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina. Universidad Nacional del Litoral. Facultad de Humanidades y Ciencias. Departamento de Ciencias Naturales; ArgentinaFil: Ghirardi, Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina. Universidad Católica de Santa Fe; ArgentinaFil: Armando, Andrea Paola. Universidad Nacional del Litoral. Facultad de Humanidades y Ciencias. Departamento de Ciencias Naturales; Argentin