francesco pegoraro - Academia.edu (original) (raw)
Papers by francesco pegoraro
SPIE Proceedings, 2015
ion acceleration, with the laser energy almost totally transferrable to the ions in the relativis... more ion acceleration, with the laser energy almost totally transferrable to the ions in the relativistic regime. There is a fundamental limit on the maximum attainable ion energy, which is determined by the group velocity of the laser. In the case of a tightly focused laser pulses, which are utilized to get the highest intensity, another factor limiting the maximum ion energy comes into play, the transverse expansion of the target. It makes the target transparent for radiation, thus reducing the effectiveness of acceleration. Utilization of an external guiding structure for the accelerating laser pulse may provide a way of compensating for the group velocity and transverse expansion effects.
Physical Review Letters, 1983
A plasma mode driven by the anisotropy of the velocity distribution of charged fusionreaction pro... more A plasma mode driven by the anisotropy of the velocity distribution of charged fusionreaction products can resonate with the spin precession frequency of one of the plasma components. When these spins are initially polarized, resonant depolarization can occur at a rate considerably faster than the fusion reaction rate, if spatial inhomogeneity effects do not depress excessively the mode amplitude.
Physical Review Letters, 2011
Physica Scripta, 2004
The quantum physics of light is a most fascinating field. Here I present a very personal viewpoin... more The quantum physics of light is a most fascinating field. Here I present a very personal viewpoint, focusing on my own path to quantum entanglement and then on to applications. I have been fascinated by quantum physics ever since I heard about it for the first time in school. The theory struck me immediately for two reasons: (1) its immense mathematical beauty, and (2) the unparalleled precision to which its predictions have been verified again and again. Particularly fascinating for me were the predictions of quantum mechanics for individual particles, individual quantum systems. Surprisingly, the experimental realization of many of these fundamental phenomena has led to novel ideas for applications. Starting from my early experiments with neutrons, I later became interested in quantum entanglement, initially focusing on multi-particle entanglement like GHZ states. This work opened the experimental possibility to do quantum teleportation and quantum hyper-dense coding. The latter became the first entanglement-based quantum experiment breaking a classical limitation. One of the most fascinating phenomena is entanglement swapping, the teleportation of an entangled state. This phenomenon is fundamentally interesting because it can entangle two pairs of particles which do not share any common past. Surprisingly, it also became an important ingredient in a number of applications, including quantum repeaters which will connect future quantum computers with each other. Another application is entanglement-based quantum cryptography where I present some recent long-distance experiments. Entanglement swapping has also been applied in very recent so-called loophole-free tests of Bell's theorem. Within the physics community such loophole-free experiments are perceived as providing nearly definitive proof that local realism is untenable. While, out of principle, local realism can never be excluded entirely, the 2015 achievements narrow down the remaining possibilities for local realistic explanations of the quantum phenomenon of entanglement in a significant way. These experiments may go down in the history books of science. Future experiments will address particularly the freedom-of-choice loophole using cosmic sources of randomness. Such experiments confirm that unconditionally secure quantum cryptography is possible, since quantum cryptography based on Bell's theorem can provide unconditional security. The fact that the experiments were loophole-free proves that an eavesdropper cannot avoid detection in an experiment that correctly follows the protocol. I finally discuss some recent experiments with single-and entangled-photon states in higher dimensions. Such experiments realized quantum entanglement between two photons, each with quantum numbers beyond 10 000 and also simultaneous entanglement of two photons where each carries more than 100 dimensions. Thus they offer the possibility of quantum communication with more than one bit or qubit per photon. The paper concludes discussing Einstein's contributions and viewpoints of quantum mechanics. Even if some of his positions are not supported by recent experiments, he has to be given credit for the fact that his analysis of fundamental issues gave rise to developments which led to a new information technology. Finally, I reflect on some of the lessons learned by the fact that Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Physica Scripta, 2000
The quantum physics of light is a most fascinating field. Here I present a very personal viewpoin... more The quantum physics of light is a most fascinating field. Here I present a very personal viewpoint, focusing on my own path to quantum entanglement and then on to applications. I have been fascinated by quantum physics ever since I heard about it for the first time in school. The theory struck me immediately for two reasons: (1) its immense mathematical beauty, and (2) the unparalleled precision to which its predictions have been verified again and again. Particularly fascinating for me were the predictions of quantum mechanics for individual particles, individual quantum systems. Surprisingly, the experimental realization of many of these fundamental phenomena has led to novel ideas for applications. Starting from my early experiments with neutrons, I later became interested in quantum entanglement, initially focusing on multi-particle entanglement like GHZ states. This work opened the experimental possibility to do quantum teleportation and quantum hyper-dense coding. The latter became the first entanglement-based quantum experiment breaking a classical limitation. One of the most fascinating phenomena is entanglement swapping, the teleportation of an entangled state. This phenomenon is fundamentally interesting because it can entangle two pairs of particles which do not share any common past. Surprisingly, it also became an important ingredient in a number of applications, including quantum repeaters which will connect future quantum computers with each other. Another application is entanglement-based quantum cryptography where I present some recent long-distance experiments. Entanglement swapping has also been applied in very recent so-called loophole-free tests of Bell's theorem. Within the physics community such loophole-free experiments are perceived as providing nearly definitive proof that local realism is untenable. While, out of principle, local realism can never be excluded entirely, the 2015 achievements narrow down the remaining possibilities for local realistic explanations of the quantum phenomenon of entanglement in a significant way. These experiments may go down in the history books of science. Future experiments will address particularly the freedom-of-choice loophole using cosmic sources of randomness. Such experiments confirm that unconditionally secure quantum cryptography is possible, since quantum cryptography based on Bell's theorem can provide unconditional security. The fact that the experiments were loophole-free proves that an eavesdropper cannot avoid detection in an experiment that correctly follows the protocol. I finally discuss some recent experiments with single-and entangled-photon states in higher dimensions. Such experiments realized quantum entanglement between two photons, each with quantum numbers beyond 10 000 and also simultaneous entanglement of two photons where each carries more than 100 dimensions. Thus they offer the possibility of quantum communication with more than one bit or qubit per photon. The paper concludes discussing Einstein's contributions and viewpoints of quantum mechanics. Even if some of his positions are not supported by recent experiments, he has to be given credit for the fact that his analysis of fundamental issues gave rise to developments which led to a new information technology. Finally, I reflect on some of the lessons learned by the fact that Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
New Aspects of Plasma Physics, 2008
Later the same concept was applied to accelerated fluids by Sir Geoffrey Taylor 2. Understanding ... more Later the same concept was applied to accelerated fluids by Sir Geoffrey Taylor 2. Understanding the rate of mixing caused by the Rayleigh-Taylor instability is important to a wide range of applications, that range from inertial confinement fusion, nuclear weapons explosions 3 , supernova explosions and supernova remnants, to oceanography and atmospheric physics, to laboratory and space plasmas etc. 2 Taylor, Sir Geoffrey Ingram,"The instability of liquid surfaces when accelerated in a direction perpendicular to their planes,"
Journal of Geophysical Research: Space Physics, 2018
We present a three‐dimensional study of the plasma dynamics at the flank magnetopause of the Eart... more We present a three‐dimensional study of the plasma dynamics at the flank magnetopause of the Earth's magnetosphere during mainly northward interplanetary magnetic field periods. Two‐fluid simulations show that the initial magnetic shear at the magnetopause and the field line bending caused by the dynamics itself (in a configuration taken as representative of the properties of the flank magnetopause) influence both the location where the Kelvin‐Helmholtz (KH) instability and the induced magnetic reconnection take place and their nonlinear development. The KH vortices develop asymmetrically with respect to the Earth's equatorial plane where the local KH linear growth rate is maximal. Vortex‐driven reconnection processes take place at different latitudes, ranging from the equatorial plane to midlatitude regions but only in the hemisphere that turns out to be the less KH unstable. These results suggest that KH‐induced reconnection is not limited to specific regions around the vo...
Physical Review D, 2015
A covariant action principle for ideal relativistic magnetohydrodynamics (MHD) in terms of natura... more A covariant action principle for ideal relativistic magnetohydrodynamics (MHD) in terms of natural Eulerian field variables is given. This is done by generalizing the covariant Poisson bracket theory of Marsden et al. [Ann. Phys. 169, 29 (1986)], which uses a noncanonical bracket to effect constrained variations of an action functional. Various implications and extensions of this action principle are also discussed. Two significant by-products of this formalism are the introduction of a new divergence-free 4-vector variable for the magnetic field, and a new Lie-dragged form for the theory.
Physical Review Letters, 2001
With the help of 2D-3V (two dimensional in space and three dimensional in velocity) Vlasov simula... more With the help of 2D-3V (two dimensional in space and three dimensional in velocity) Vlasov simulations we show that the magnetic field generated by the electromagnetic current filamentation instability develops magnetic islands due to the onset of a fast reconnection process that occurs on the electron dynamical time scale. This process is relevant to magnetic channel coalescence in relativistic laser plasma interactions.
Physical Review Special Topics - Accelerators and Beams, 2003
In 1998 Bulanov et al. [Phys. Rev. E 58, R5257 (1998)] proposed a novel scheme for the production... more In 1998 Bulanov et al. [Phys. Rev. E 58, R5257 (1998)] proposed a novel scheme for the production of high-quality electron beams in laser wakefield acceleration in which a controlled longitudinal nonlinear wave breaking is induced by a tailored electron density profile. This proposal was supported by both analytical and numerical results in a spatially one-dimensional configuration. In this paper we present results of a particle-in-cell simulation, two-dimensional in space and three-dimensional in the fields, of the interaction of an ultraintense laser pulse with a preformed plasma where the electron density decreases steeply from a first to a second plateau. We show that in our regime two-dimensional effects play a relevant role, allowing the production of well collimated, short and almost monochromatic electron beam. Remarkably low values of transverse and longitudinal normalized beam emittance tr rms 9 10 ÿ2 mm mrad and lon rms 2 mm keV are obtained.
Symmetry, Integrability and Geometry: Methods and Applications, 2006
Plasma Sources Science and Technology, 2008
A space plasma experiment is discussed which consists of a magnetized plasma bubble interacting w... more A space plasma experiment is discussed which consists of a magnetized plasma bubble interacting with the ambient (ionospheric) plasma. The magnetized plasma inside the magnetized bubble is tied to the dipole magnetic field generated inside the satellite. The parameters of the bubble are discussed in relation to the parameters of the ambient plasma and the plasma regimes and phenomena that can be investigated are indicated.
Plasma Physics and Controlled Fusion, 2005
Physics of Plasmas, 2013
Numerical and experimental evidence is given for the occurrence of the plateau states and concomi... more Numerical and experimental evidence is given for the occurrence of the plateau states and concomitant corner modes proposed in Valentini et al. [Phys. Plasmas 19, 092103 (2012)]. It is argued that these states provide a better description of reality for small amplitude off-dispersion disturbances than the conventional Bernstein-Greene-Kruskal or cnoidal states such as those proposed in Schamel [Phys. Plasmas 20, 034701 (2013)].
Physics of Plasmas, 2010
We discuss a new family of solutions of the Grad–Shafranov (GS) equation that describes D-shaped ... more We discuss a new family of solutions of the Grad–Shafranov (GS) equation that describes D-shaped toroidal plasma equilibria with sharp gradients at the plasma edge. These solutions have been derived by exploiting the continuous Lie symmetry properties of the GS equation and in particular a special type of “weak” symmetries. In addition, we review the continuous Lie symmetry properties of the GS equation and present a short but exhaustive survey of the possible choices for the arbitrary flux functions that yield GS equations admitting some continuous Lie symmetry. Particular solutions related to these symmetries are also discussed.
Physics of Plasmas, 2012
The noncanonical Hamiltonian formulation of magnetohydrodynamics (MHD) is used to construct varia... more The noncanonical Hamiltonian formulation of magnetohydrodynamics (MHD) is used to construct variational principles for continuously symmetric equilibrium configurations of magnetized plasma, including flow. In particular, helical symmetry is considered, and results on axial and translational symmetries are retrieved as special cases of the helical configurations. The symmetry condition, which allows the description in terms of a magnetic flux function, is exploited to deduce a symmetric form of the noncanonical Poisson bracket of MHD. Casimir invariants are then obtained directly from the Poisson bracket. Equilibria are obtained from an energy-Casimir principle and reduced forms of this variational principle are obtained by the elimination of algebraic constraints.
Physics Letters A, 2002
Previous Previous article Next Next article Check if you have access through your login credentia... more Previous Previous article Next Next article Check if you have access through your login credentials or your institution.
Physical Review Letters, 1995
The results of a two-dimensional particle-in-cell simulation and of an analytical description of ... more The results of a two-dimensional particle-in-cell simulation and of an analytical description of the propagation in an underdense plasma of a short, relativistically intense, laser pulse are presented. Selffocusing is proven in an ultrarelativistic regime for moderately long pulses. Pulses shorter than the plasma wavelength, but wider than it, excite a wake wave with a regular electric field. The electron density in the wake has a "horseshoe" shape and focuses a long pulse locally. The excitation of stimulated Raman backward scattering is observed.
SPIE Proceedings, 2015
ion acceleration, with the laser energy almost totally transferrable to the ions in the relativis... more ion acceleration, with the laser energy almost totally transferrable to the ions in the relativistic regime. There is a fundamental limit on the maximum attainable ion energy, which is determined by the group velocity of the laser. In the case of a tightly focused laser pulses, which are utilized to get the highest intensity, another factor limiting the maximum ion energy comes into play, the transverse expansion of the target. It makes the target transparent for radiation, thus reducing the effectiveness of acceleration. Utilization of an external guiding structure for the accelerating laser pulse may provide a way of compensating for the group velocity and transverse expansion effects.
Physical Review Letters, 1983
A plasma mode driven by the anisotropy of the velocity distribution of charged fusionreaction pro... more A plasma mode driven by the anisotropy of the velocity distribution of charged fusionreaction products can resonate with the spin precession frequency of one of the plasma components. When these spins are initially polarized, resonant depolarization can occur at a rate considerably faster than the fusion reaction rate, if spatial inhomogeneity effects do not depress excessively the mode amplitude.
Physical Review Letters, 2011
Physica Scripta, 2004
The quantum physics of light is a most fascinating field. Here I present a very personal viewpoin... more The quantum physics of light is a most fascinating field. Here I present a very personal viewpoint, focusing on my own path to quantum entanglement and then on to applications. I have been fascinated by quantum physics ever since I heard about it for the first time in school. The theory struck me immediately for two reasons: (1) its immense mathematical beauty, and (2) the unparalleled precision to which its predictions have been verified again and again. Particularly fascinating for me were the predictions of quantum mechanics for individual particles, individual quantum systems. Surprisingly, the experimental realization of many of these fundamental phenomena has led to novel ideas for applications. Starting from my early experiments with neutrons, I later became interested in quantum entanglement, initially focusing on multi-particle entanglement like GHZ states. This work opened the experimental possibility to do quantum teleportation and quantum hyper-dense coding. The latter became the first entanglement-based quantum experiment breaking a classical limitation. One of the most fascinating phenomena is entanglement swapping, the teleportation of an entangled state. This phenomenon is fundamentally interesting because it can entangle two pairs of particles which do not share any common past. Surprisingly, it also became an important ingredient in a number of applications, including quantum repeaters which will connect future quantum computers with each other. Another application is entanglement-based quantum cryptography where I present some recent long-distance experiments. Entanglement swapping has also been applied in very recent so-called loophole-free tests of Bell's theorem. Within the physics community such loophole-free experiments are perceived as providing nearly definitive proof that local realism is untenable. While, out of principle, local realism can never be excluded entirely, the 2015 achievements narrow down the remaining possibilities for local realistic explanations of the quantum phenomenon of entanglement in a significant way. These experiments may go down in the history books of science. Future experiments will address particularly the freedom-of-choice loophole using cosmic sources of randomness. Such experiments confirm that unconditionally secure quantum cryptography is possible, since quantum cryptography based on Bell's theorem can provide unconditional security. The fact that the experiments were loophole-free proves that an eavesdropper cannot avoid detection in an experiment that correctly follows the protocol. I finally discuss some recent experiments with single-and entangled-photon states in higher dimensions. Such experiments realized quantum entanglement between two photons, each with quantum numbers beyond 10 000 and also simultaneous entanglement of two photons where each carries more than 100 dimensions. Thus they offer the possibility of quantum communication with more than one bit or qubit per photon. The paper concludes discussing Einstein's contributions and viewpoints of quantum mechanics. Even if some of his positions are not supported by recent experiments, he has to be given credit for the fact that his analysis of fundamental issues gave rise to developments which led to a new information technology. Finally, I reflect on some of the lessons learned by the fact that Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Physica Scripta, 2000
The quantum physics of light is a most fascinating field. Here I present a very personal viewpoin... more The quantum physics of light is a most fascinating field. Here I present a very personal viewpoint, focusing on my own path to quantum entanglement and then on to applications. I have been fascinated by quantum physics ever since I heard about it for the first time in school. The theory struck me immediately for two reasons: (1) its immense mathematical beauty, and (2) the unparalleled precision to which its predictions have been verified again and again. Particularly fascinating for me were the predictions of quantum mechanics for individual particles, individual quantum systems. Surprisingly, the experimental realization of many of these fundamental phenomena has led to novel ideas for applications. Starting from my early experiments with neutrons, I later became interested in quantum entanglement, initially focusing on multi-particle entanglement like GHZ states. This work opened the experimental possibility to do quantum teleportation and quantum hyper-dense coding. The latter became the first entanglement-based quantum experiment breaking a classical limitation. One of the most fascinating phenomena is entanglement swapping, the teleportation of an entangled state. This phenomenon is fundamentally interesting because it can entangle two pairs of particles which do not share any common past. Surprisingly, it also became an important ingredient in a number of applications, including quantum repeaters which will connect future quantum computers with each other. Another application is entanglement-based quantum cryptography where I present some recent long-distance experiments. Entanglement swapping has also been applied in very recent so-called loophole-free tests of Bell's theorem. Within the physics community such loophole-free experiments are perceived as providing nearly definitive proof that local realism is untenable. While, out of principle, local realism can never be excluded entirely, the 2015 achievements narrow down the remaining possibilities for local realistic explanations of the quantum phenomenon of entanglement in a significant way. These experiments may go down in the history books of science. Future experiments will address particularly the freedom-of-choice loophole using cosmic sources of randomness. Such experiments confirm that unconditionally secure quantum cryptography is possible, since quantum cryptography based on Bell's theorem can provide unconditional security. The fact that the experiments were loophole-free proves that an eavesdropper cannot avoid detection in an experiment that correctly follows the protocol. I finally discuss some recent experiments with single-and entangled-photon states in higher dimensions. Such experiments realized quantum entanglement between two photons, each with quantum numbers beyond 10 000 and also simultaneous entanglement of two photons where each carries more than 100 dimensions. Thus they offer the possibility of quantum communication with more than one bit or qubit per photon. The paper concludes discussing Einstein's contributions and viewpoints of quantum mechanics. Even if some of his positions are not supported by recent experiments, he has to be given credit for the fact that his analysis of fundamental issues gave rise to developments which led to a new information technology. Finally, I reflect on some of the lessons learned by the fact that Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
New Aspects of Plasma Physics, 2008
Later the same concept was applied to accelerated fluids by Sir Geoffrey Taylor 2. Understanding ... more Later the same concept was applied to accelerated fluids by Sir Geoffrey Taylor 2. Understanding the rate of mixing caused by the Rayleigh-Taylor instability is important to a wide range of applications, that range from inertial confinement fusion, nuclear weapons explosions 3 , supernova explosions and supernova remnants, to oceanography and atmospheric physics, to laboratory and space plasmas etc. 2 Taylor, Sir Geoffrey Ingram,"The instability of liquid surfaces when accelerated in a direction perpendicular to their planes,"
Journal of Geophysical Research: Space Physics, 2018
We present a three‐dimensional study of the plasma dynamics at the flank magnetopause of the Eart... more We present a three‐dimensional study of the plasma dynamics at the flank magnetopause of the Earth's magnetosphere during mainly northward interplanetary magnetic field periods. Two‐fluid simulations show that the initial magnetic shear at the magnetopause and the field line bending caused by the dynamics itself (in a configuration taken as representative of the properties of the flank magnetopause) influence both the location where the Kelvin‐Helmholtz (KH) instability and the induced magnetic reconnection take place and their nonlinear development. The KH vortices develop asymmetrically with respect to the Earth's equatorial plane where the local KH linear growth rate is maximal. Vortex‐driven reconnection processes take place at different latitudes, ranging from the equatorial plane to midlatitude regions but only in the hemisphere that turns out to be the less KH unstable. These results suggest that KH‐induced reconnection is not limited to specific regions around the vo...
Physical Review D, 2015
A covariant action principle for ideal relativistic magnetohydrodynamics (MHD) in terms of natura... more A covariant action principle for ideal relativistic magnetohydrodynamics (MHD) in terms of natural Eulerian field variables is given. This is done by generalizing the covariant Poisson bracket theory of Marsden et al. [Ann. Phys. 169, 29 (1986)], which uses a noncanonical bracket to effect constrained variations of an action functional. Various implications and extensions of this action principle are also discussed. Two significant by-products of this formalism are the introduction of a new divergence-free 4-vector variable for the magnetic field, and a new Lie-dragged form for the theory.
Physical Review Letters, 2001
With the help of 2D-3V (two dimensional in space and three dimensional in velocity) Vlasov simula... more With the help of 2D-3V (two dimensional in space and three dimensional in velocity) Vlasov simulations we show that the magnetic field generated by the electromagnetic current filamentation instability develops magnetic islands due to the onset of a fast reconnection process that occurs on the electron dynamical time scale. This process is relevant to magnetic channel coalescence in relativistic laser plasma interactions.
Physical Review Special Topics - Accelerators and Beams, 2003
In 1998 Bulanov et al. [Phys. Rev. E 58, R5257 (1998)] proposed a novel scheme for the production... more In 1998 Bulanov et al. [Phys. Rev. E 58, R5257 (1998)] proposed a novel scheme for the production of high-quality electron beams in laser wakefield acceleration in which a controlled longitudinal nonlinear wave breaking is induced by a tailored electron density profile. This proposal was supported by both analytical and numerical results in a spatially one-dimensional configuration. In this paper we present results of a particle-in-cell simulation, two-dimensional in space and three-dimensional in the fields, of the interaction of an ultraintense laser pulse with a preformed plasma where the electron density decreases steeply from a first to a second plateau. We show that in our regime two-dimensional effects play a relevant role, allowing the production of well collimated, short and almost monochromatic electron beam. Remarkably low values of transverse and longitudinal normalized beam emittance tr rms 9 10 ÿ2 mm mrad and lon rms 2 mm keV are obtained.
Symmetry, Integrability and Geometry: Methods and Applications, 2006
Plasma Sources Science and Technology, 2008
A space plasma experiment is discussed which consists of a magnetized plasma bubble interacting w... more A space plasma experiment is discussed which consists of a magnetized plasma bubble interacting with the ambient (ionospheric) plasma. The magnetized plasma inside the magnetized bubble is tied to the dipole magnetic field generated inside the satellite. The parameters of the bubble are discussed in relation to the parameters of the ambient plasma and the plasma regimes and phenomena that can be investigated are indicated.
Plasma Physics and Controlled Fusion, 2005
Physics of Plasmas, 2013
Numerical and experimental evidence is given for the occurrence of the plateau states and concomi... more Numerical and experimental evidence is given for the occurrence of the plateau states and concomitant corner modes proposed in Valentini et al. [Phys. Plasmas 19, 092103 (2012)]. It is argued that these states provide a better description of reality for small amplitude off-dispersion disturbances than the conventional Bernstein-Greene-Kruskal or cnoidal states such as those proposed in Schamel [Phys. Plasmas 20, 034701 (2013)].
Physics of Plasmas, 2010
We discuss a new family of solutions of the Grad–Shafranov (GS) equation that describes D-shaped ... more We discuss a new family of solutions of the Grad–Shafranov (GS) equation that describes D-shaped toroidal plasma equilibria with sharp gradients at the plasma edge. These solutions have been derived by exploiting the continuous Lie symmetry properties of the GS equation and in particular a special type of “weak” symmetries. In addition, we review the continuous Lie symmetry properties of the GS equation and present a short but exhaustive survey of the possible choices for the arbitrary flux functions that yield GS equations admitting some continuous Lie symmetry. Particular solutions related to these symmetries are also discussed.
Physics of Plasmas, 2012
The noncanonical Hamiltonian formulation of magnetohydrodynamics (MHD) is used to construct varia... more The noncanonical Hamiltonian formulation of magnetohydrodynamics (MHD) is used to construct variational principles for continuously symmetric equilibrium configurations of magnetized plasma, including flow. In particular, helical symmetry is considered, and results on axial and translational symmetries are retrieved as special cases of the helical configurations. The symmetry condition, which allows the description in terms of a magnetic flux function, is exploited to deduce a symmetric form of the noncanonical Poisson bracket of MHD. Casimir invariants are then obtained directly from the Poisson bracket. Equilibria are obtained from an energy-Casimir principle and reduced forms of this variational principle are obtained by the elimination of algebraic constraints.
Physics Letters A, 2002
Previous Previous article Next Next article Check if you have access through your login credentia... more Previous Previous article Next Next article Check if you have access through your login credentials or your institution.
Physical Review Letters, 1995
The results of a two-dimensional particle-in-cell simulation and of an analytical description of ... more The results of a two-dimensional particle-in-cell simulation and of an analytical description of the propagation in an underdense plasma of a short, relativistically intense, laser pulse are presented. Selffocusing is proven in an ultrarelativistic regime for moderately long pulses. Pulses shorter than the plasma wavelength, but wider than it, excite a wake wave with a regular electric field. The electron density in the wake has a "horseshoe" shape and focuses a long pulse locally. The excitation of stimulated Raman backward scattering is observed.