336 research outputs found
All the supersymmetric configurations of N=4,d=4 supergravity
All the supersymmetric configurations of pure, ungauged, N=4,d=4 supergravity
are classified in a formalism that keeps manifest the S and T dualities of the
theory. We also find simple equations that need to be satisfied by the
configurations to be classical solutions of the theory. While the solutions
associated to null Killing vectors were essentially classified by Tod (a
classification that we refine), we find new configurations and solutions
associated to timelike Killing vectors that do not satisfy Tod's rigidity
hypothesis (hence, they have a non-trivial U(1) connection) and whose
supersymmetry projector is associated to 1-dimensional objects (strings),
although they have a trivial axion field.Comment: Latex file, 47 pages. References added and a few non-essential
misprints correcte
How to excite the internal modes of sine-Gordon solitons
We investigate the dynamics of the sine-Gordon solitons perturbed by
spatiotemporal external forces. We prove the existence of internal (shape)
modes of sine-Gordon solitons when they are in the presence of inhomogeneous
space-dependent external forces, provided some conditions (for these forces)
hold. Additional periodic time-dependent forces can sustain oscillations of the
soliton width. We show that, in some cases, the internal mode even can become
unstable, causing the soliton to decay in an antisoliton and two solitons. In
general, in the presence of spatiotemporal forces the soliton behaves as a
deformable (non-rigid) object. A soliton moving in an array of inhomogeneities
can also present sustained oscillations of its width. There are very important
phenomena (like the soliton-antisoliton collisions) where the existence of
internal modes plays a crucial role. We show that, under some conditions, the
dynamics of the soliton shape modes can be chaotic. A short report of some of
our results has been published in [J. A. Gonzalez et al., Phys. Rev. E, 65
(2002) 065601(R)].Comment: 14 .eps figures.To appear in Chaos, Solitons and Fractal
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