18 research outputs found
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
Goldstone models in D+1 dimensions, D=3,4,5, supporting stable and zero topological charge solutions
We study finite energy static solutions to a global symmetry breaking
Goldstone model described by an isovector scalar field in D+1 spacetime
dimensions. Both topologically stable multisolitons with arbitrary winding
numbers, and zero topological charge soliton--antisoliton solutions are
constructed numerically in D=3,4,5. We have explored the types of symmetries
the systems should be subjected to, for there to exist multisoliton and
soliton--antisoliton pairs in D=3,4,5,6. These findings are underpinned by
constructing numerical solutions in the examples. Subject to axial
symmetry, only multisolitons of all topological charges exist in even D, and in
odd D, only zero and unit topological charge solutions exist. Subjecting the
system to weaker than axial symmetries, results in the existence of all the
possibilities in all dimensions. Our findings apply also to finite 'energy'
solutions to Yang--Mills and Yang-Mills--Higgs systems, and in principle also
sigma models.Comment: 29 pages, 6 figure
Stationary Dyonic Regular and Black Hole Solutions
We consider globally regular and black hole solutions in SU(2)
Einstein-Yang-Mills-Higgs theory, coupled to a dilaton field. The basic
solutions represent magnetic monopoles, monopole-antimonopole systems or black
holes with monopole or dipole hair. When the globally regular solutions carry
additionally electric charge, an angular momentum density results, except in
the simplest spherically symmetric case. We evaluate the global charges of the
solutions and their effective action, and analyze their dependence on the
gravitational coupling strength. We show, that in the presence of a dilaton
field, the black hole solutions satisfy a generalized Smarr type mass formula.Comment: 23 pages, 4 figure
Classical Yang-Mills Black hole hair in anti-de Sitter space
The properties of hairy black holes in Einstein–Yang–Mills (EYM) theory are reviewed, focusing on spherically symmetric solutions. In particular, in asymptotically anti-de Sitter space (adS) stable black hole hair is known to exist for frak su(2) EYM. We review recent work in which it is shown that stable hair also exists in frak su(N) EYM for arbitrary N, so that there is no upper limit on how much stable hair a black hole in adS can possess
Monopole-Antimonopole Solutions of the Skyrmed SU(2) Yang-Mills-Higgs Model
Axially symmetric monopole anti-monopole dipole solutions to the second order equations of a simple SU(2) Yang-Mills-Higgs model featuring a quartic Skyrme-like term are constructed numerically. The effect of varying the Skyrme coupling constant on these solutions is studied in some detail
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