43,647 research outputs found
On spherically symmetrical accretion in fractal media
We use fractional integrals to generalize the description of hydrodynamic
accretion in fractal media. The fractional continuous medium model allows the
generalization of the equations of balance of mass density and momentum
density. These make it possible to consider the general case of spherical
hydrodynamic accretion onto a gravitating mass embedded in a fractal medium.
The general nature of the solution is similar to the "Bondi solution", but the
accretion rate may vary substantially and the dependence on central mass may
change significantly depending on dimensionality of the fractal medium. The
theory shows consistency with the observational data and numerical simulation
results for the particular case of accretion onto pre-main-sequence stars.Comment: 5 pages, 2 figures. Accepted for publication in MNRAS Letters. The
definitive version is available at http://www.blackwell-synergy.co
A peridynamic theory for linear elastic shells
A state-based peridynamic formulation for linear elastic shells is presented.
The emphasis is on introducing, possibly for the first time, a general surface
based peridynamic model to represent the deformation characteristics of
structures that have one physical dimension much smaller than the other two. A
new notion of curved bonds is exploited to cater for force transfer between the
peridynamic particles describing the shell. Starting with the three dimensional
force and deformation states, appropriate surface based force, moment and
several deformation states are arrived at. Upon application on the curved
bonds, such states beget the necessary force and deformation vectors governing
the motion of the shell. Correctness of our proposal on the peridynamic shell
theory is numerically assessed against static deformation of spherical and
cylindrical shells and flat plates
Correlated few-photon transport in one-dimensional waveguides: linear and nonlinear dispersions
We address correlated few-photon transport in one-dimensional waveguides
coupled to a two-level system (TLS), such as an atom or a quantum dot. We
derive exactly the single-photon and two-photon current (transmission) for
linear and nonlinear (tight-binding sinusoidal) energy-momentum dispersion
relations of photons in the waveguides and compare the results for the
different dispersions. A large enhancement of the two-photon current for the
sinusoidal dispersion has been seen at a certain transition energy of the TLS
away from the single-photon resonances.Comment: 6 pages, 5 figures, revised version, to appear in Phys. Rev.
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