Plasmon dispersion and Landau damping in the nonlinear quantum regime.

We study the dispersion properties of electron plasma waves, or plasmons, which can be excited in quantum plasmas in the nonlinear regime. In order to describe nonlinear electron response to finite amplitude plasmons, we apply the Volkov approach to nonrelativistic electrons. For that purpose, we use the Schrödinger equation and describe the electron population of a quantum plasma as a mixture of quantum states. Within the kinetic framework that we are able to derive from the Volkov solutions, we discuss the role of the wave amplitude on the nonlinear plasma response. Finally, we focus on the quantum properties of nonlinear Landau damping and study the contributions of multiplasmon absorption and emission processes.

Bose-Einstein condensation of photons in microcavity plasmas.

Bose-Einstein condensation of a finite number of photons propagating inside a plasma-filled microcavity is investigated. The nonzero chemical potential is provided by the electrons, which induces a finite photon mass and allows condensation to occur. We derive an equation that models the evolution of the photon-mode occupancies, with Compton scattering taken into account as the mechanism of thermalization. The kinetic evolution of the photon spectrum is solved numerically, and we find evidence of condensation down to nanosecond timescales for typical microplasma conditions, n_{e}∼10^{14}-10^{15}cm^{-3}. The critical temperature scales almost linearly with the number of photons, and we find high condensate fractions at microcavity-plasma temperatures, for experimentally achievable cavity lengths (100-500µm) and photon numbers (10^{10}-10^{12}).

Controlled beat-wave Brillouin scattering in the ionosphere.

Stimulated Brillouin scattering experiments in the ionospheric plasma using a single electromagnetic pump wave have previously been observed to generate an electromagnetic sideband wave, emitted by the plasma, together with an ion- acoustic wave. Here we report results of a controlled, pump and probe beat-wave driven Brillouin scattering experiment, in which an ion-acoustic wave generated by the beating of electromagnetic pump and probe waves, results in electromagnetic sideband waves that are recorded on the ground. The experiment used the EISCAT facility in northern Norway, which has several high power electromagnetic wave transmitters and receivers in the radio frequency range. An electromagnetic pump consisting of large amplitude radio waves with ordinary (O) or extraordinary (X) mode polarization was injected into the overhead ionosphere, along with a less powerful probe wave, and radio sideband emissions observed on the ground clearly show stimulated Brillouin emissions at frequencies agreeing with, and changing with, the pump and probe frequencies. The experiment was simulated using a numerical full-scale model which clearly supports the interpretation of the experimental results. Such controlled beat-wave experiments demonstrate a way of remotely investigating the ionospheric plasma parameters.

Photon bubble turbulence in cold atom gases.

Turbulent radiation flow is commonplace in systems with strong, incoherent, light-matter interactions. In astrophysical contexts, photon bubble turbulence is considered a key mechanism behind enhanced radiation transport, and its importance has been widely asserted for a variety of high energy objects such as accretion disks and massive stars. Here, we show that analogous conditions to those of dense astrophysical objects can be obtained in large clouds of cold atoms, prepared in a laser-cooling experiment, driven close to a sharp electronic resonance. By accessing the spatially-resolved atom density, we are able to identify a photon bubble instability and the resulting regime of photon bubble turbulence. We also develop a theoretical model describing the coupled dynamics of both photon and atom gases, which accurately describes the statistical properties of the turbulent regime. This study thus opens the possibility of simulating radiation-dominated astrophysical systems in cold atom experiments.

Optical Control of the Topology of Laser-Plasma Accelerators.

We propose a twisted plasma accelerator capable of generating relativistic electron vortex beams with helical current profiles. The angular momentum of these vortex bunches is quantized, dominates their transverse motion, and results in spiraling particle trajectories around the twisted wakefield. We focus on a laser wakefield acceleration scenario, driven by a laser beam with a helical spatiotemporal intensity profile, also known as a light spring. We find that these light springs can rotate as they excite the twisted plasma wakefield, providing a new mechanism to control the twisted wakefield phase velocity and enhance energy gain and trapping efficiency beyond planar wakefields.

Plasmon excitations with a semi-integer angular momentum.

We provide an explicit model for a spin-1/2 quasi-particle, based on the superposition of plasmon excitations in a quantum plasmas with intrinsic orbital angular momentum. Such quasi-particle solutions can show remarkable similarities with single electrons moving in vacuum: they have spin-1/2, a finite rest mass, and a quantum dispersion. We also show that these quasi-particle solutions satisfy a criterium of energy minimum.

Axion-Plasmon Polaritons in Strongly Magnetized Plasmas.

Axions are hypothetical particles related to the violation of the charge-parity symmetry within the strong sector of the standard model, being one of the most prone candidates for dark matter. Multiple attempts to prove their existence are currently performed in different physical systems. Here, we predict that axions may couple to the electrostatic (Langmuir) modes of a strongly magnetized plasma, and show that a new quasiparticle can be defined, the axion-plasmon polariton. The excitation of axions can be inferred from the pronounced modification of the dispersion relation of the Langmuir waves, a feature that we estimate to be accessible in state-of-the-art plasma-based experiments.

Tonks-Dattner resonances in a quantum plasma bubble.

We establish the spectrum of Tonks-Dattner mode resonances in a quantum plasma bubble and consider the spectral changes associated with plasma quenching and plasma expansion. The quantum corrections associated with the mode spectrum are specified, which can be used as a diagnostic tool to identify the quantum regime. The frequency shifts associated with time-varying plasma bubbles correspond to time refraction and can also be used as a plasma diagnostic. We also study the energy mode coupling, in the presence of a low-frequency perturbation. It will be shown that the mode coupling equations take the form of generalized Bloch equations, where a nonlinear Rabi frequency can also be identified.

Amplification and generation of ultra-intense twisted laser pulses via stimulated Raman scattering.

Twisted Laguerre-Gaussian lasers, with orbital angular momentum and characterized by doughnut-shaped intensity profiles, provide a transformative set of tools and research directions in a growing range of fields and applications, from super-resolution microcopy and ultra-fast optical communications to quantum computing and astrophysics. The impact of twisted light is widening as recent numerical calculations provided solutions to long-standing challenges in plasma-based acceleration by allowing for high-gradient positron acceleration. The production of ultra-high-intensity twisted laser pulses could then also have a broad influence on relativistic laser-matter interactions. Here we show theoretically and with ab initio three-dimensional particle-in-cell simulations that stimulated Raman backscattering can generate and amplify twisted lasers to petawatt intensities in plasmas. This work may open new research directions in nonlinear optics and high-energy-density science, compact plasma-based accelerators and light sources.

High Orbital Angular Momentum Harmonic Generation.

We identify and explore a high orbital angular momentum (OAM) harmonics generation and amplification mechanism that manipulates the OAM independently of any other laser property, by preserving the initial laser wavelength, through stimulated Raman backscattering in a plasma. The high OAM harmonics spectra can extend at least up to the limiting value imposed by the paraxial approximation. We show with theory and particle-in-cell simulations that the orders of the OAM harmonics can be tuned according to a selection rule that depends on the initial OAM of the interacting waves. We illustrate the high OAM harmonics generation in a plasma using several examples including the generation of prime OAM harmonics. The process can also be realized in any nonlinear optical Kerr media supporting three-wave interactions.

Quasi-polaritons in Bose-Einstein condensates induced by Casimir-Polder interaction with graphene.

We consider the mechanical coupling between a two-dimensional Bose-Einstein condensate and a graphene sheet via the vacuum fluctuations of the electromagnetic field which are at the origin of the so-called Casimir-Polder potential. By deriving a self-consistent set of equations governing the dynamics of the condensate and the flexural (out-of-plane) modes of the graphene, we can show the formation of a new type of purely acoustic quasi-particle excitation, a quasi-polariton resulting from the coherent superposition of quanta of flexural and Bogoliubov modes.

Management of fishing of the Broadband Anchovy (Anchoviella lepidentostole) (Fowler, 1911), in south São Paulo state, Brazil / Gestão da pesca de Manjuba (Anchoviella lepidentostole) (Fowler, 1911) no sul do estado de São Paulo, Brasil

The broadband anchovy (Anchoviella lepidentostole) is one of the most important fishery resources for economic and social development of Iguape City and for the whole of the south coast of São Paulo state. Nowadays this activity involves over 2,500 fishermen. This paper aims to evaluate its fishing, and discuss how the activity is managed. In order to conduct this study, production data and catch per unit effort (CPUE) data from the 1998-2000 period have been collected, and the characterisation of the activity has also been done. A decline in broadband anchovy abundance had been observed in the region up until 2004, when a new regulation was implemented, in an attempt to recover the resource, with the establishment of closed season fishing (defeso) during the catch season, and adjustments in the employed fishing gear. The results have shown a recovery of the abundance of broadband anchovy throughout the 2005-2010 period, showing thus far that the measures taken for the maintenance of the resource have been successful. The activity has been managed through discussions involving people from the fishing sector in order to determine the controversial actions to be taken, that are hard to enforce. In order to achieve a more satisfactory resource management, it is necessary to keep the participatory process, with adaptive co-management, based on discussion among all the sectors involved (from government and society), and constant monitoring of the activity.

A manjuba (Anchoviella lepidentostole) é um dos recursos pesqueiros de maior importância econômica e social para todo litoral sul do Estado de São Paulo, com mais de 2.500 pescadores envolvidos. O presente trabalho visa avaliar sua pesca e a discutir a gestão da atividade. Para isto, foram coletados dados de produção e CPUE das capturas do período de 1998 a 2010, bem como a caracterização da atividade. Observou-se queda da abundância de manjuba na região até o ano de 2004, quando foi implementada nova normativa, na tentativa de recuperar o recurso, com o estabelecimento de período de defeso no meio da safra e ajustes nas artes de pesca empregadas. Os resultados mostraram uma recuperação da abundância da manjuba ao longo do período de 2005 a 2010, indicando, até o momento que as ações tomadas para a manutenção do recurso tem tido sucesso. Houve uma gestão da atividade através de discussão junto ao setor para determinação de ações polêmicas e de difícil implementação. Para uma gestão do recurso mais satisfatória, é necessário desenvolver melhor o processo participativo, com um co-manejo adaptativo, que tem base na discussão entre todos os setores envolvidos (governo e sociedade) e o monitoramento constante da atividade.

Inverse bremsstrahlung in relativistic quantum plasmas.

We study the absorption of an intense electromagnetic wave in a plasma by inverse bremsstrahlung, in the relativistic quantum regime, by using the Klein-Gordon (KG) equation. We examine the following points: (1) the solutions of the KG equation in the absence of collisions; (2) the transition probabilities between electron momentum states, and (3) the effective collision frequency in the weak and strong field limits.

Management of fishing of the broadband anchovy (Anchoviella lepidentostole) (Fowler, 1911), in south São Paulo State, Brazil.

The broadband anchovy (Anchoviella lepidentostole) is one of the most important fishery resources for economic and social development of Iguape City and for the whole of the south coast of São Paulo state. Nowadays this activity involves over 2,500 fishermen. This paper aims to evaluate its fishing, and discuss how the activity is managed. In order to conduct this study, production data and catch per unit effort (CPUE) data from the 1998-2000 period have been collected, and the characterisation of the activity has also been done. A decline in broadband anchovy abundance had been observed in the region up until 2004, when a new regulation was implemented, in an attempt to recover the resource, with the establishment of closed season fishing (defeso) during the catch season, and adjustments in the employed fishing gear. The results have shown a recovery of the abundance of broadband anchovy throughout the 2005-2010 period, showing thus far that the measures taken for the maintenance of the resource have been successful. The activity has been managed through discussions involving people from the fishing sector in order to determine the controversial actions to be taken, that are hard to enforce. In order to achieve a more satisfactory resource management, it is necessary to keep the participatory process, with adaptive co-management, based on discussion among all the sectors involved (from government and society), and constant monitoring of the activity.

Photon bubbles in ultracold matter.

We show that static and oscillating photon bubbles can be excited by diffused light in the laser cooled matter confined in a magneto-optical trap. The bubble instability is due to the coupling between the radiation field and the mean field oscillations of the ultracold gas, and it can provide a source for low frequency turbulence. We consider a diffusion-dominated regime, which can be described by a radiation transport equation, coupled with the mean field equations for the cold atom gas. A perturbative analysis shows the occurrence of two different regimes with either oscillating or purely growing bubbles. This work could also be useful to understand similar processes in astrophysics.

Assessment and management of white mullet Mugil curema (Valencienne, 1836) (Mugilidae) fisheries of the south coast of São Paulo state, Brazil.

There is intense fishing activity, mainly artisanal, in the Cananéia, Iguape and Ilha Comprida Estuarine System. White mullet (Mugil curema) is one of the local fishery resources and is usually caught with gillnets and fish traps. This study aimed to characterise the Mugil curema fisheries thereby underpinning the management of the species in the region. The study was developed with data collected from landings in the town of Cananéia, São Paulo state, Brazil, from 1995 to 2009. Production data, fishing effort and CPUE were used to assess the evolution of captures. The gillnets were characterised by interviewing fishermen from 16 communities in Cananéia. White mullet fishery has aroused the interest of fishermen in the region since the 80s and today it is one of the main products of artisanal estuarine fishery off the south coast of São Paulo. The major landings occur in the warmer months with fish traps and gillnets being the main fishing gear used. The largest catches occur in the spawning months of the species from October to April. The highest landings varied according to different fishing gear, showing differences primarily due to trade preferences and to the structure of the fishing gear. According to the index of abundance used in this study, the resource is overfished due to the progressive increase in fishing effort, so it is suggested that measures should be taken to control fishing effort, such as special fishing permits to catch white mullet, especially with gillnets. The current management measures neither meet the needs of fishermen nor the preservation of the resource, and must be reviewed in a participatory way with management agencies and the fishery sector, ensuring greater legitimacy and success in the sustainability of the activity.

Volkov solutions for relativistic quantum plasmas.

This work studies the electron quantum states, as determined by the Dirac equation, in the field of electrostatic and electromagnetic waves in a plasma. We discuss the main differences with respect to the vacuum case, and the assumptions under which the vacuum Volkov solutions can be adapted to a plasma. The case of ultrashort electromagnetic wave pulses is also discussed. We also consider the electron states in the field of an electron plasma wave. Modified Volkov solutions of the Dirac equation can also be found. For electron plasma waves such that the phase velocity becomes close to the speed of light, these solutions are exact. Finally, we consider electron states in the field of two waves in a plasma, with relevance to the mixed case where one of the waves is electrostatic and the other is electromagnetic.

Inverse Faraday effect with linearly polarized laser pulses.

The inverse Faraday effect is usually associated with circularly polarized radiation; here, we show that it can also occur for linearly polarized radiation. The quasistatic axial magnetic field generated by a laser propagating in plasma can be calculated by considering both the spin and the orbital angular momenta of the laser pulse. A net spin is present when the radiation is circularly polarized and a net orbital angular momentum is present if there is any deviation from perfect rotational symmetry. The orbital angular momentum gives an additional contribution to the axial magnetic field that can enhance or reduce the effect usually attributed to circular polarization and strongly depends on the intensity profile of the Laguerre-Gaussian modes involving the azimuthal and radial mode numbers.

Evaluation and management of blue crab Callinectes sapidus (Rathbun, 1896) (Decapoda-Portunidae) fishery in the Estuary of Cananéia, Iguape and Ilha Comprida, São Paulo, Brazil.

The Estuary of Cananéia, Iguape and Ilha Comprida is a part of the Estuarine Lagoon System of Cananéia, Iguape and Paranaguá, on the south coast of São Paulo State, Brazil. It has been recognised for its high standards of environmental conservation. The objective of this paper was to assess the blue crab (Callinectes sapidus) fishing in the region, from January 1998 to December 2006, and obtain supportive data to implement technical rules for the rational exploitation and resulting conservation of this resource. The results show a remarkable decrease in the fisheries' abundance index (CPUE) up to 2005, from 9.4 to 4.0 kg/hour, mainly caused by an increase in fishing effort, from 1,960 to 13,776 hours on a yearly basis. With the decrease in the fishing effort in 2005 and 2006, the abundance index reacted positively, indicating a recovery of the exploited population. Due to the lack of appropriate regulation limiting the fishing effort and organising the fluctuating admission rates of new fishermen, there is a noticeable increase of the effort, above the sustainable level. Therefore, there is a need for measures to limit and control the admission of fishermen in this activity. One of the measures to be considered is the establishment of regular periods where fishing the species is prohibited (called 'defeso'), each year, especially from September to January. Another measure is to create a fishermen registry and special licenses, to limit the number of new entrants. Such actions require, for their implementation, a co-managed initiative, involving the blue crab fishermen themselves, governmental agencies and resource management researchers, and the integration of ecological, socioeconomic and cultural dimensions.

Mangrove oyster (Crassostrea spp.) (Sacco, 1897) extractivism in Cananéia estuary (São Paulo, Brazil) from 1999 to 2006: capture and management evaluation.

The oyster Crassostrea spp. is one of the main fisheries resources in the southern portion of São Paulo State. This paper aims to evaluate the extractivism of that resource, supplying subsidies to the implementation of management regulations. This study was developed in Cananéia, from February 1999 to December 2006. The oyster production data in dozens was obtained through weekly or monthly interviews. The annual and average CPUE in dozens per day was analysis to verify significant differences along years. There are no regulations that limit the fishing effort or organize the admission in the fishermen. The admission is controlled by the condition of the market and there is a risk of increasing the fishing effort above the sustainable yield, which demands measures that control the number of fishermen engaged in the activity. Those measures, to be effective, must be created in discussion with the fisheries sector, based on technical information.