Solitons and soliton-antisoliton pairs of a Goldstone model in 3+1 dimensions

We study finite energy static solutions to a global symmetry breaking model in 3+1 dimensions described by an isovector scalar field. The basic features of two different types of configurations are discussed, one of them corresponding to axially symmetric multisolitons with topological charge $n$, and the other one to unstable soliton-antisoliton pairs with zero topological charge.Comment: 13 pages, 5 figure

Armenian Civil Society: It is Not All about NGOs

For the past two decades, Armenian civil society was largely equated with the NGO sector. International development organizations, public officials, scholars and the few informed among the general public saw NGOs as the core element of Armenian civil society. The NGO sector is by now fairly developed and institutionalised, but it is detached from the broader Armenian society, remaining a post-communist civil society in that sense. However, recently a new actor has entered the arena of civil society and made its presence very visible. The socalled “civic initiatives” are on the rise since around 2007, and have already registered a number of successes in impacting government decisions, despite the small numbers of people involved. Armenian civil society is no more simply about NGOs, though NGOs unquestionably remain a very important component of civil society

Pulse propagation, population transfer and light storage in five-level media

We consider adiabatic interaction of five-level atomic systems and their media with four short laser pulses under the condition of all two-photon detunings being zero. We derive analytical expressions for eigenvalues of the system's Hamiltonian and determine conditions of adiabaticity for both the atom and the medium. We analyse, in detail, the system's behaviour when the eigenvalue with non-vanishing energy is realized. As distinct from the usual dark state of a five-level system (corresponding to zero eigenvalue), which is a superposition of three states, in our case the superposition of four states does work. This seemingly unfavourable case is nevertheless demonstrated to imitate completely a three-level system not only for a single atom but also in the medium, since the propagation equations are also split into those for three- and two-level media separately. We show that, under certain conditions, all the coherent effects observed in three-level media, such as population transfer, light slowing, light storage, and so on, may efficiently be realized in five-level media. This has an important advantage that the light storage can be performed twice in the same medium, i.e., the second pulse can be stored without retrieving the first one, and then the two pulses can be retrieved in any desired sequence

Short Pulse Propagation in an Inverted Two-Level Medium

We consider propagation of a pulse carrying optical information in a resonant medium of twolevel atoms and revisit the concept of the group velocity. We obtain conditions when this concept may be used and show that in a population inverted medium the possible superluminal propagation may result in advance times much shorter than the pulse duration because of lethargic amplification following from the complete exact solution of the problem

The 1-soliton in the SO(3) gauged Skyrme model with mass term

The solitons of the SO(3) gauged Skyrme model with no pion-mass potential were studied in Refs. {nl,jmp}. Here, the effects of the inclusion of this potential are studied. In contrast with the (ungauged) Skyrme model, where the effect of this potential on the solitons is marginal, here it turns out to be decisive, resulting in very different dependence of the energy as a function of the Skyrme coupling constant.Comment: new title, typos corrected, LaTeX, 8 pages, 4 figure

Spinning U(1) gauged Skyrmions

We construct axially symmetric solutions of U(1) gauged Skyrme model. Possessing a nonvanishing magnetic moment, these solitons have also a nonzero angular momentum proportional to the electric charge.Comment: v2: 7 pages, 4 eps figures; some clarifications and references added on the existence of solutions; typos correcte

Gravitating Stationary Dyons and Rotating Vortex Rings

We construct dyons, and electrically charged monopole-antimonopole pairs and vortex rings in Yang-Mills-Higgs theory coupled to Einstein gravity. The solutions are stationary, axially symmetric and asymptotically flat. The dyons with magnetic charge $n\ge 2$ represent non-static solutions with vanishing angular momentum. The electrically charged monopole-antimonopole pairs and vortex rings, in contrast, possess vanishing magnetic charge, but finite angular momentum, equaling $n$ times their electric charge.Comment: 2 references adde