547 research outputs found
Self-action in Gravity
On a particle moving with variable acceleration in the flat space-time
affects the self-force due to outgoing radiation. The gravitational fields
bring an additional contribution to self-force due to scattering waves on the
curved backgrounds. This force is not zero even for a particle at rest. A
review of the self-interaction in the gravitational field is presented. We
consider the self-force for the particle connected with the vector and scalar
fields. Different backgrounds are considered -- black holes, stars, topological
defects, and wormholes.Comment: 65 page
Semiclassical wormholes
Smooth-throat wormholes are treated on as possessing quantum fluctuation
energy with scalar massive field as its source. Heat kernel coefficients of the
Laplace operator are calculated in background of the arbitrary-profile throat
wormhole with the help of the zeta-function approach. Two specific profile are
considered. Some arguments are given that the wormholes may exist. It serves as
a solution of semiclassical Einstein equations in the range of specific values
of length and certain radius of wormhole's throat and constant of non-minimal
connection.Comment: 28 pages, 4 figures, revtex
Van der Waals interaction between an atom with spherical plasma shell
We consider the van der Waals energy of an atom near the infinitely thin
sphere with finite conductivity which model the fullerene. We put the sphere
into spherical cavity inside the infinite dielectric media, then calculate the
energy of vacuum fluctuations in framework of the zeta-function approach. The
energy for a single atom is obtained from this expression by consideration of
the rare media. In the limit of the infinite radius of the sphere the
Casimir-Polder expression for an atom and plate is recovered. For finite radius
of sphere the energy of an atom monotonously falls down as close to
the sphere and far from the sphere. For hydrogen atom on the surface
of the fullerene we obtain that the energy is . We obtain also
that the polarizability of fullerene is merely cube of its radius.Comment: 10 pages, 5 figure
Modeling of interstitial branching of axonal networks
A single axon can generate branches connecting with plenty synaptic targets.
Process of branching is very important for making connections in central
nervous system. The interstitial branching along primary axon shaft occurs
during nervous system development. Growing axon makes pause in its movement and
leaves active points behind its terminal. The new branches appear from these
points. We suggest mathematical model to describe and investigate neural
network branching process. The model under consideration describes neural
network growth in which the concentration of axon guidance molecules manages
axon's growth. We model the interstitial branching from axon shaft. Numerical
simulations show that in the model framework axonal networks are similar to
neural network.Comment: 12 pages, 7 figure
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