878 research outputs found
Two types of generalized integrable decompositions and new solitary-wave solutions for the modified Kadomtsev-Petviashvili equation with symbolic computation
The modified Kadomtsev-Petviashvili (mKP) equation is shown in this paper to
be decomposable into the first two soliton equations of the 2N-coupled
Chen-Lee-Liu and Kaup-Newell hierarchies by respectively nonlinearizing two
sets of symmetry Lax pairs. In these two cases, the decomposed
(1+1)-dimensional nonlinear systems both have a couple of different Lax
representations, which means that there are two linear systems associated with
the mKP equation under the same constraint between the potential and
eigenfunctions. For each Lax representation of the decomposed (1+1)-dimensional
nonlinear systems, the corresponding Darboux transformation is further
constructed such that a series of explicit solutions of the mKP equation can be
recursively generated with the assistance of symbolic computation. In
illustration, four new families of solitary-wave solutions are presented and
the relevant stability is analyzed.Comment: 23 page
Particle Collisions on Stringy Black Hole Background
The collision of two particles in the background of a Sen black hole is
studied. With the equations of motion of the particles, the center-of-mass
energy is investigated when the collision takes place at the horizon of a Sen
black hole. For an extremal Sen black hole, we find that the center-of-mass
energy will be arbitrarily high with two conditions: (1) spin and (2)
one of the colliding particles has the critical angular momentum
. For a nonextremal Sen black hole, we show that, in order to
obtain an unlimited center-of-mass energy, one of the colliding particles
should have the critical angular momentum ( is
the radius of the outer horizon for a nonextremal black hole). However, a
particle with the angular momentum could not approach the
black hole from outside of the horizon through free fall, which implies that
the collision with arbitrarily high center-of-mass energy could not take place.
Thus, there is an upper bound of the center-of-mass energy for the nonextremal
black hole. We also obtain the maximal center-of-mass energy for a
near-extremal black hole and the result implies that the Planck-scale energy is
hard to be approached. Furthermore, we also consider the back-reaction effects.
The result shows that, neglecting the gravitational radiation, it has a weak
effect on the center-of-mass energy. However, we argue that the maximum allowed
center-of-mass energy will be greatly reduced to below the Planck-scale when
the gravitational radiation is included.Comment: 17 pages, 4 figures, published versio
Efficient community-based control strategies in adaptive networks
Most researches on adaptive networks mainly concentrate on the properties of
steady state, but neglect transient dynamics. In this study, we pay attention
to the emergence of community structures in transient process and the effects
of community-based control strategies on epidemic spreading. First, by
normalizing modularity , we investigate the evolution of community
structures during the transient process, and find that very strong community
structures are induced by rewiring mechanism in the early stage of epidemic
spreading, which remarkably delays the outbreaks of epidemic. Then we study the
effects of control strategies started from different stages on the prevalence.
Both immunization and quarantine strategies indicate that it is not "the
earlier, the better" for the implementing of control measures. And the optimal
control effect is obtained if control measures can be efficiently implemented
in the period of strong community structure. For immunization strategy,
immunizing the S nodes on SI links and immunizing S nodes randomly have similar
control effects. Yet for quarantine strategy, quarantining the I nodes on SI
links can yield far better effects than quarantining I nodes randomly. More
significantly, community-based quarantine strategy plays more efficient
performance than community-based immunization strategy. This study may shed new
lights on the forecast and the prevention of epidemic among human population.Comment: 5 pages, 5 figure
Quasiparticle Scattering Interference in High Temperature Superconductors
We propose that the energy-dependent spatial modulation of the local density
of states seen by Hoffman, et al [hoff2] is due to the scattering interference
of quasiparticles. In this paper we present the general theoretical basis for
such an interpretation and lay out the underlying assumptions. As an example,
we perform exact T-matrix calculation for the scattering due to a single
impurity. The results of this calculation is used to check the assumptions, and
demonstrate that quasiparticle scattering interference can indeed produce
patterns similar to those observed in Ref. [hoff2].Comment: RevTex4 twocolumn, 4 pages, 3 figures. Figs.2-3 virtually embedded
(bacause of too big size) while jpg files available in the postscript/source
package. Further polishe
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