Spark Model for Pulsar Radiation Modulation Patterns

A non-stationary polar gap model first proposed by Ruderman & Sutherland (1975) is modified and applied to spark-associated pulsar emission at radio wave-lengths. It is argued that under physical and geometrical conditions prevailing above pulsar polar cap, highly non-stationary spark discharges do not occur at random positions. Instead, sparks should tend to operate in well determined preferred regions. At any instant the polar cap is populated as densely as possible with a number of two-dimensional sparks with a characteristic dimension as well as a typical distance between adjacent sparks being about the polar gap height. Our model differs, however, markedly from its original 'hollow cone' version. The key feature is the quasi-central spark driven by pair production process and anchored to the local pole of a sunspot-like surface magnetic field. This fixed spark prevents the motion of other sparks towards the pole, restricting it to slow circumferential drift across the planes of field lines converging at the local pole. We argue that the polar spark constitutes the core pulsar emission, and that the annular rings of drifting sparks contribute to conal components of the pulsar beam. We found that the number of nested cones in the beam of typical pulsar should not excced three; a number also found by Mitra & Deshpande (1999) using a completely different analysis.Comment: 31 pages, 8 figures, accepted by Ap

Exclusão e abandono em uma liga de futebol infantil e juvenil na Argentina

Resumen: Introducción: El fútbol infantil y juvenil es un fenómeno cultural y social de gran importancia en Argentina. Objetivo: Este trabajo tiene como objetivo dar cuenta de aspectos fundamentales de la estructura organizativa del fútbol infantil y juvenil en la liga de Mar del Plata, una de las ciudades más importantes del país. Métodos: El análisis de datos cuantitativos básicos permite dar cuenta de los aspectos fundamentales de la estructura organizativa del fútbol infantil y juvenil en esta liga. Este análisis elemental de cuantitativo se combina con una interpretación de informes basada tanto en un análisis discursivo como etnográfico. Resultados y discusión: Existe un severo proceso de exclusión y abandono en la liga de fútbol de Mar del Plata (LMF). No sólo ocurre que el número de jugadoras mujeres es extremadamente bajo en comparación con el número de jugadores varones, sino que también ocurre que más de mil varones son abandonados año tras año por la LMF. El complejo proceso de abandono y exclusión también está fuertemente ligado a una serie de fenómenos diversos, como el sexismo, la ausencia de personas con discapacidad, la imitación de prácticas de fútbol profesional y el uso de etiquetas y estereotipos. Conclusiones: Dado que promueve sistemáticamente la exclusión y el abandono, el LMF no puede cumplir una función educativa o inclusiva, y ni siquiera puede ayudar a formar jugadores profesionales de alto nivel. En su estado actual, la estructura organizativa de la LMF debería implementar algunas transformaciones radicales pero plausibles.Abstract: Introduction: Children’s and youth football is a cultural and social phenomenon of huge importance in Argentina. Aim: This work aims at accounting for fundamental aspects of the organizational structure of children’s and youth football in the league of Mar del Plata, one of the most important cities in the country. Methods: The analysis of basic quantitative data enables us to account for the fundamental aspects of the organizational structure of children’s and youth football in the league of Mar del Plata. This elementary quantitative analysis is combined with an interpretation of reports based both on a discursive and an ethnographic analysis. Results & discussion: There is a severe process of exclusion and abandonment in the Mar del Plata football league (MFL). Not only it is the case that the number of female players is extremely low compared to the number of male players, but it is also the case that more than a thousand male players are abandoned year after year by the MFL. The complex process of abandonment and exclusion is also strongly connected with a series of diverse phenomena, like sexism, the absence of people with disabilities, the imitation of professional football practices, and the use of labels and stereotypes. Conclusions: Since it systematically promotes exclusion and abandonment, the MFL cannot fulfill an educational or inclusive function, and cannot even help to form high-level professional players. In its current state, the organizational structure of the MFL should apply some radical but plausible transformations.Resumo: Introdução: O futebol infantil e juvenil é um fenômeno cultural e social de grande importância na Argentina. Objetivo: Este trabalho visa dar conta dos aspectos fundamentais da estrutura organizacional do futebol infanto-juvenil da liga de Mar del Plata, uma das cidades mais importantes do país. Métodos: A análise de dados quantitativos básicos permite dar conta dos aspectos fundamentais da estrutura organizacional do futebol infanto-juvenil desta liga. Esta análise quantitativa elementar é combinada com uma interpretação de relatórios com base na análise discursiva e etnográfica. Resultados e discussão: Há um severo processo de exclusão e abandono no campeonato de futebol de Mar del Plata (LMF). Não só o número de jogadoras femininas é extremamente baixo em comparação com o número de jogadores masculinos, mas também acontece que mais de mil jogadores masculinos são abandonados ano após ano pela LMF. O complexo processo de abandono e exclusão também está fortemente ligado a uma série de fenômenos diversos, como o sexismo, a ausência de pessoas com deficiência, a imitação de práticas profissionais do futebol e o uso de rótulos e estereótipos. Conclusões: Por promover sistematicamente a exclusão e o abandono, o LMF não pode cumprir uma função educativa ou inclusiva e nem mesmo pode ajudar na formação de jogadores profissionais de alto nível. Em seu estado atual, a estrutura organizacional do MFL deve aplicar algumas transformações radicais, mas plausíveis

Frequency dependence of pulsar radiation patterns

We report on new results from simultaneous, dual frequency, single pulse observation of PSR B0329+54 using the Giant Metrewave Radio Telescope. We find that the longitude separation of subpulses at two different frequencies (238 and 612 MHz) is less than that for the corresponding components in the average profile. A similar behaviour has been noticed before in a number of pulsars. We argue that subpulses are emitted within narrow flux tubes of the dipolar field lines and that the mean pulsar beam has a conal structure. In such a model the longitudes of profile components are determined by the intersection of the line of sight trajectory with subpulse-associated emission beams. Thus, we show that the difference in the frequency dependence of subpulse and profile component longitudes is a natural property of the conal model of pulsar emission beam. We support our conclusions by numerical modelling of pulsar emission, using the known parameters for this pulsar, which produce results that agree very well with our dual frequency observations.Comment: 24 pages, 8 figures. Accepted for publication in Ap

The spark-associated soliton model for pulsar radio emission

We propose a new, self-consistent theory of coherent pulsar radio emission based on the non-stationary sparking model of Ruderman & Sutherland (1975), modified by Gil & Sendyk (2000) in the accompanying Paper I. According to these authors, the polar cap is populated as densely as possible by a number of sparks with a characteristic perpendicular dimension D approximately equal to the polar gap height scale h, separated from each other also by about h. Each spark reappears in approximately the same place on the polar cap for a time scale much longer than its life-time and delivers to the open magnetosphere a sequence of electron-positron clouds which flow orderly along a flux tube of dipolar magnetic field lines. The overlapping of particles with different momenta from consecutive clouds leads to effective two-stream instability, which triggers electrostatic Langmuir waves at the altitudes of about 50 stellar radii. The electrostatic oscillations are modulationally unstable and their nonlinear evolution results in formation of ``bunch-like'' charged solitons. A characteristic soliton length along magnetic field lines is about 30 cm, so they are capable of emitting coherent curvature radiation at radio wavelengths. The net soliton charge is about 10^21 fundamental charges, contained within a volume of about 10^14 cm^3. For a typical pulsar, there are about 10^5 solitons associated with each of about 25 sparks operating on the polar cap at any instant. One soliton moving relativisticaly along dipolar field lines with a Lorentz factor of the order of 100 generates a power of about 10^21 erg/s by means of curvature radiation. Then the total power of a typical radio pulsar can be estimated as being about 10^(27-28) erg/s.Comment: 27 pages, 5 figures, accepted by Ap

Multiple cyclical fractional structures in financial time series

This paper analyses multiple cyclical structures in financial time series. In particular, we focus on the monthly structure of the Nasdaq, the Dow Jones and the Standard&Poor stock market indices. The three series are modelled as long-memory processes with poles in the spectrum at multiple frequencies, including the long-run or zero frequency

Stability analysis for the background equations for inflation with dissipation and in a viscous radiation bath

The effects of bulk viscosity are examined for inflationary dynamics in which dissipation and thermalization are present. A complete stability analysis is done for the background inflaton evolution equations, which includes both inflaton dissipation and radiation bulk viscous effects. Three representative approaches of bulk viscous irreversible thermodynamics are analyzed: the Eckart noncausal theory, the linear and causal theory of Israel-Stewart and a more recent nonlinear and causal bulk viscous theory. It is found that the causal theories allow for larger bulk viscosities before encountering an instability in comparison to the noncausal Eckart theory. It is also shown that the causal theories tend to suppress the radiation production due to bulk viscous pressure, because of the presence of relaxation effects implicit in these theories. Bulk viscosity coefficients derived from quantum field theory are applied to warm inflation model building and an analysis is made of the effects to the duration of inflation. The treatment of bulk pressure would also be relevant to the reheating phase after inflation in cold inflation dynamics and during the radiation dominated regime, although very little work in both areas has been done, the methodology developed in this paper could be extended to apply to these other problems.Comment: 27 pages, 14 figures, Published version JCA