[en] It is shown that the possibilities of manipulating microobjects can be considerably extended by using beams with preset intensity and orbital momentum distributions in the focusing plane. The results of experiments on the transfer of the orbital momentum of such beams to microparticles are presented. (letters)

[en] Any irregularities that occur in the structure of a collapsing cloud will produce non-radial gravitational forces and, if such irregularities are sheared by differential rotation into trailing spiral features of large amplitude, the associated gravitational torques will transfer angular momentum outward on an orbital time-scale. Even if no redistribution of angular momentum occurs during the collapse and a flattened disc-like configuration is formed, such a disc will be a fragile structure at best, and with realistic initial conditions it will be highly unstable to the development of trailing spiral density enhancements. Thus it seems inescapable that in a realistic collapsing cloud there will sooner or later occur rapid outward transfer of angular momentum by gravitational torques. The only stable outcome of the collapse will then be a system in which most of the mass is in a central star or binary system, and less than half remains in a disc around the star; less than one-quarter can remain in a disc with the size of our Solar System. (author)

[en] In this paper I present an overview of the favoured scenario explaining the presence of twin cylindrical astrophysical jets in the vicinity of accretion discs. These jets are made of plasma and host large-scale magnetic fields. The twin jets flow away from the accreting system in opposite directions, perpendicular to the plane of the accretion disc. In the scenario presented in this paper, the accretion disc interacts with the magnetic field in such a way that the disc angular momentum is removed from the disc and transported away along the magnetic field lines. Such a transport is the source of the jet phenomenon as the angular momentum is given back to a tiny amount of material extracted from the disc. This outflow is then powered by the disc rotation as the disc is able to enter an accretion motion where matter releases its gravitational energy. The angular momentum carried by the jet is actually present through the existence of an electric current. In the jet cylindrical geometry, the presence of this current is able to provide a collimating mechanism where the magnetic field pinches the plasma column. This mechanism is very close to the one acting in tokamak reactors. Apart from explaining how the plasma outflow is able to be self-confined by the magnetic field present in the flow, this scenario is also able to explain how jet mass can be accelerated thanks to the magnetohydrodynamics Poynting flux escaping from the disc. In this presentation I finally present the constraints arising from the scenario, in particular upon the turbulent transport coefficient required to get a steady structure.

[en] The study of nuclear reactions that are important for the understanding of astrophysical problems received an increasing attention over the last decades. The Trojan Horse Method was proposed as a tool to overcome some of the problems connected with the measurement of cross-sections between charged particles at astrophysical energies. Here we present some recent studies on this method. (authors)

[en] The transfer of angular momentum between the bar and halo components of a galaxy is computed using both analytic dynamical friction theory and 'semi-restricted' n-body simulations. The two methods yield results which are in qualitative agreement and demonstrate that dynamical friction can exert strong torques on galactic bars. A rotating rigid bar with typical parameters initially ending at corotation slows down in several bar rotation times in the presence of an isothermal halo. This rapid angular momentum transfer implies that the corotation radius must be far beyond the end of the bar unless: (1) angular momentum is added to the bar (i.e. by the disc) allowing an equilibrium bar pattern speed to be reached; (2) the galactic halo is small or non-existent; or (3) the bar is weak. (author)

[en] In this paper we shall use the Random Walk procedure to accelerate the tracking of the particles which have a large number of collision events. This method is based on the approximation of Fleck's transport equation by a diffusion equation using the multiple scale technique. The chapter is organized as follows: In Sec. I we derive the transfer equation satisfied by a Monte-Carlo particle and the corresponding diffusion equation, the explicit solution of which is known in a sphere. We calculate the probability of escaping from the sphere and the probability of remaining inside at the end of the time step in Sec. 2. We study some criteria for the validity of this approximation in Sec. 3, using Monte-Carlo calculations in the sphere. Numerical results are given in Sec. 4

[en] It is shown that the spiral patterns which develop spontaneously in computer models of galaxies are generated through angular momentum transfer. By adjusting the distribution of mass in the rigid halo components of the models it is possible to alter radically the rotation curve of the disc component. Either trailing or leading spiral arms develop in the models, dependent only on the sense of the differential shear; no spirals are seen in models where the disc rotates uniformly. It is found that the distribution of angular momentum in the disc is altered by the spiral evolution. Although some spiral structure can be seen for a long period, the life of each pattern is very short. It is shown that resonances are of major importance even for these transient patterns. All spiral wave patterns which have been seen possess both an inner Lindblad resonance and a co-rotation resonance. (author)

[en] It is shown that (1) the proper framework for testing Rastall's theory and its generalisations is in the case of non-negligible (i.e. discernible) gravitational effects such as gravity gradients; 2) these theories have conserved integral four-momentum and angular momentum; and (3) the Nordtvedt effect then provides limits on the parameters which arise as the result of the non-zero divergence of the energy-momentum tensor. (author)

[en] A small sample of short-period binary stars suggests that their angular-momentum-loss (AML) rates are proportional to Psup(-1.2). AML rates of single slowly rotating stars depend much more strongly on rotational period (approx.= P^-3). Extrapolations of AML rates from slow rotators to rapidly rotating systems might be erroneous. (author)

[en] This paper provides a concise summary of the current status of the research and future perspectives discussed in the Mini-Conference on Angular Momentum Transport in Laboratory and Nature. This Mini-conference, sponsored by the Topical Group on Plasma Astrophysics, was held as part of the American Physical Society's Division of Plasma Physics 2007 Annual Meeting (November 12-16, 2007). This Mini-conference covers a wide range of phenomena happening in fluids and plasmas, either in laboratory or in nature. The purpose of this paper is not to comprehensively review these phenomena, but to provide a starting point for interested readers to refer to related research in areas other than their own