External Vacuum Field Research Articles

Collective excitations of atoms and field modes in coupled cavities

The exact solution for the system formed from two or three q-bits doped in coupled cavities is discussed. The problem of indistinguishability between the excited radiators and the photons is analyzed using the intrinsic symmetry of the system. It is demonstrated that the solution is drastically simplified when the radiators and photons are considered as new polariton excitations. The exact solution of the Schrödinger equation is obtained for single and two excitations in each cavity considering the indistinguishability principle. This approach opens new possibilities for the interpretation of quantum entangled states in comparison with the traditional distinct situation (see e.g. Napoli and Messina 2001 Fortschr. Phys. 49 1059; Enaki and Bazgan 2013 Phys. Scr. T153 014022) due to the decrease in the number of degrees of freedom in the system. Considering that the energy of coupling between the radiators and the photons is larger than that of the coupling with an external vacuum field, we have found the master equation for the dumping of collective excitations. The time dependence of the population for new dressed quasi-levels of energy is obtained by solving the master equation analytically and numerically.

Hall equilibria with toroidal and poloidal fields: application to neutron stars

We present solutions for Hall equilibria applicable to neutron star crusts. Such magnetic configurations satisfy a Grad-Shafranov-type equation, which is solved analytically and numerically. The solutions presented cover a variety of configurations, from purely poloidal fields connected to an external dipole to poloidal-toroidal fields connected to an external vacuum field, or fully confined within the star. We find that a dipole external field should be supported by a uniformly rotating electron fluid. The energy of the toroidal magnetic field is generally found to be a few percent of the total magnetic field energy for the fields with an external component. We discuss the evolution due to Ohmic dissipation which leads to slowing down of the electron fluid. We also find that the transition from an MHD equilibrium to a state governed by Hall effect, generates spontaneously an additional toroidal field in regions where the electron fraction changes.

Free-boundary, high-beta equilibrium in a large aspect ratio tokamak with nearly circular plasma boundary

An analytic solution is obtained for free-boundary, high-beta equilibria in large aspect ratio tokamaks with a nearly circular plasma boundary. In the absence of surface currents at the plasma-vacuum interface, the free-boundary equilibrium solution introduces constraints arising from the need to couple to an external vacuum field which is physically realizable with a reasonable set of external field coils. This places a strong constraint on the pressure profiles that are consistent with a given boundary shape at high εβp. The equilibrium solution also provides information on the flux surface topology. The plasma is bounded by a separatrix. Increasing the plasma pressure at fixed total current causes the plasma aperture to decrease in a manner that is described.

A note on black hole and naked singularity

Recently THORNY. (~) and LIANG (2) have independently constructed explicit models of cylindrical dust collapsing into the naked singularity (a) of an external vacuum field. There are also indications that similar models can exist even with pressure (4). Although such models may be too artificial because of their cylindrical symmetry, it seems that, at least for the moment, the possibility of gravitational collapse into a naked singularity should be considered. If both black hole and naked singularity arc going r stay, one question naturally arises: what is the dividing line between the initial physical conditions that will lead to one or the other? Before we can try to attack this extremely difficult problem it seems logical to first find out more about the intrinsic differences between singularities which are ~ hidden ~) behind event horizons (3) and those which are naked (a). In this note we briefly report some preliminary findings obtained after analyzing a large number of known exact solutions. We then propose a conjecture based on these results. True or not, we hope that further studies along the lines of this conjecture may bring about deeper insights into the nature of things. We deal exclusively with asymptotically flat (~) space-times and singularities at which curvature invariants and matter variables blow up. In maximally extended space-times there are usually more than one connected component of the singularity. So whenever we say ~ a ~ singularity it is understood that we are referring to one partitular component. In order to define invariant concepts we also limit ourselves to consider only geodesic normal singularity (5) (GNS), namely, singularity which admits a unique 3-parameter congruence of (spacelike or timelike) irrotational geodesics that strike it simultaneously. At present, singularities of most, if not all, known exact solu

Calculation of the Singularities of a Magnetic Field

This work is concerned with one problem which arises when finding the external magnetic field necessary to support a hydromagnetic configuration. If the hydromagnetic configuration is given without regard to the vacuum field that contains it, then that external vacuum field will in general have singularities at a finite distance from the fluid-vacuum boundary. The location of these singularities is considered. This is a good thing to know since it provides the essential limitation to the position of the external current system that ultimately contains the fluid.