The electrostatic instability for realistic pair distributions in blazar/EBL cascades

This work revisits the electrostatic instability for blazar-induced pair beams propagating through IGM with the methods of linear analysis and PIC simulations. We study the impact of the realistic distribution function of pairs resulting from interaction of high-energy gamma-rays with the extragalactic background light. We present analytical and numerical calculations of the linear growth rate of the instability for arbitrary orientation of wave vectors. Our results explicitly demonstrate that the finite angular spread of the beam dramatically affects the growth rate of the waves, leading to fastest growth for wave vectors quasi-parallel to the beam direction and a growth rate at oblique directions that is only by a factor of 2-4 smaller compared to the maximum. To study the non-linear beam relaxation, we performed PIC simulations that take into account a realistic wide-energy distribution of beam particles. The parameters of the simulated beam-plasma system provide an adequate physical picture that can be extrapolated to realistic blazar-induced pairs. In our simulations the beam looses only 1\% percent of its energy, and we analytically estimate that the beam would lose its total energy over about $100$ simulation times. Analytical scaling is then used to extrapolate to the parameters of realistic blazar-induced pair beams. We find that they can dissipate their energy slightly faster by the electrostatic instability than through inverse-Compton scattering. The uncertainties arising from, e.g., details of the primary gamma-ray spectrum are too large to make firm statements for individual blazars, and an analysis based on their specific properties is required.Comment: Accepted for publication in ApJ (2018), in prin

Positive Psychology Cinemeducation: A review of Happy

The documentary film, Happy, offers educators and practitioners a unique opportunity to provide a novel learning experience for students and clients. The film integrates meaningful stories and expert interviews with quality filmmaking to offer viewers knowledge, entertainment, and engagement. Cinematic elevation, the process by which a viewer observes virtuous behavior, feels physiological sensations of inspiration, and is consequently motivated to do good or to be a better person (e.g., copying the strengths of the film character) is particularly at play in Happy. Where there are gaps in the film’s scope of the field of happiness, wellbeing, and positive psychology, suggestions are made for the viewer to overcome these and maximize the potential to derive benefit from the film

Mindful living: Character strengths interventions as pathways for the five mindfulness trainings.

The “Five Mindfulness Trainings” of Thich Nhat Hanh (1993) have been pursued and practiced by countless individuals over the years. The core of the trainings is mindful living, in which individuals apply heightened awareness to their relationships, health behaviors, and activities of daily life, while considering the impact of these on society. The VIA character strengths, found to be universally valued and endorsed across cultures and nations, can serve as pathways to pursue these mindfulness trainings. Positive psychology interventions designed to enhance the synergy between character strengths and the mindfulness trainings are offered

The character-driven person: how frozen's Anna, not Elsa, is an exemplar

We argue that the character of Anna in the Disney animated feature film Frozen, when examined through the lens of character strengths, is one of the strongest characters in recent film history. Nevertheless it is notable, on both sides of the Atlantic, that consumers (young girls and adults alike) have a particular fascination with the older sister Elsa, viewing her as the beloved character of the film

Cosmic-Ray Acceleration at Ultrarelativistic Shock Waves: Effects of Downstream Short-Wave Turbulence

The present paper is the last of a series studying the first-order Fermi acceleration processes at relativistic shock waves with the method of Monte Carlo simulations applied to shocks propagating in realistically modeled turbulent magnetic fields. The model of the background magnetic field structure of Niemiec & Ostrowski (2004, 2006) has been augmented here by a large-amplitude short-wave downstream component, imitating that generated by plasma instabilities at the shock front. Following Niemiec & Ostrowski (2006), we have considered ultrarelativistic shocks with the mean magnetic field oriented both oblique and parallel to the shock normal. For both cases simulations have been performed for different choices of magnetic field perturbations, represented by various wave power spectra within a wide wavevector range. The results show that the introduction of the short-wave component downstream of the shock is not sufficient to produce power-law particle spectra with the "universal" spectral index 4.2. On the contrary, concave spectra with cutoffs are preferentially formed, the curvature and cutoff energy being dependent on the properties of turbulence. Our results suggest that the electromagnetic emission observed from astrophysical sites with relativistic jets, e.g. AGN and GRBs, is likely generated by particles accelerated in processes other than the widely invoked first-order Fermi mechanism.Comment: 9 pages, 8 figures, submitted to Ap

Kinetics of three-dimensional normal grain growth

Kinetics of three-dimensional normal grain growth and related processes (e.g., soap froth evolutions) described by the Mulheran–Harding model is studied. The model is represented by a diffusion equation with the grain–size–dependent diffusion coefficient. The equation is solved for an arbitrary initial distribution of grain sizes. It is proved that asymptotic kinetics do not depend on the initial state

On modeling of growth processes driven by velocity fluctuations

In the classical theory of diffusion limited growth, it is assumed that the concentration field of solution is described by the standard diffusion equation. It means that particles of the solution undergo a random walk described by the Wiener process. In turn, it means that the velocity of particles is a stochastic process being Gaussian white noise. In consequence, the velocity–velocity correlation function is the Dirac -function and velocity correlation time is zero. In many cases such modeling is insufficient and one should consider models in which velocity is correlated in space and/or time. The question is whether correlations of velocity can change the kinetics of growth, in particular, whether the long-time asymptotics of the growth kinetics displays the power-law time dependence with the classical exponent 1/2. How to model such processes is a subject of this paper

Evolution of a grain system : from early to late stages

An analytical approach to the d-dimensional grain growth, which is a kind of the heterogeneous nucleation-and-growth phase transformation, is offered. The system is assumed to be driven by capillary forces. Another important operative assumption is that the system evolves under preservation of its hypervolume, which results in considering the process as a random walk in the space of grain sizes. A role of the initial condition imposed on the system behaviour, and how does the system behave upon a prescribed initial state, have been examined. A general conclusion appears, which states that this prescription does not affect the asymptotic system behavior, but may be of importance when inspecting the early-time domain more carefully, cf. the Weibull-type initial distribution. This study is addressed to some analogous theoretical descriptions concerning polycrystals as well as bubbles-containing systems. Some comparison to another modelling, in which a crucial role of local material gradients (fluxes) was emphasized, has been attache

Kinetics of microdomain formation in two dimensional assemblies

A novel phenomenological approach to the microdomain structure formation or phase transformation in two-dimensional cooperative systems is proposed. The theory offered states that a new structure consists of pieces of islands, microdomains, germs, etc. and deals with modeling of the pattern formation process with increase of area of a new structure or phase. The kinetics of the process is studied. Probabilistic characteristics are obtained and first three moments of the process are analyzed