1,359 research outputs found
Radiative cooling in numerical astrophysics: the need for adaptive mesh refinement
Energy loss through optically thin radiative cooling plays an important part
in the evolution of astrophysical gas dynamics and should therefore be
considered a necessary element in any numerical simulation. Although the
addition of this physical process to the equations of hydrodynamics is
straightforward, it does create numerical challenges that have to be overcome
in order to ensure the physical correctness of the simulation. First, the
cooling has to be treated (semi-)implicitly, owing to the discrepancies between
the cooling timescale and the typical timesteps of the simulation. Secondly,
because of its dependence on a tabulated cooling curve, the introduction of
radiative cooling creates the necessity for an interpolation scheme. In
particular, we will argue that the addition of radiative cooling to a numerical
simulation creates the need for extremely high resolution, which can only be
fully met through the use of adaptive mesh refinement.Comment: 11 figures. Accepted for publication in Computers & Fluid
Magnetic operations: a little fuzzy physics?
We examine the behaviour of charged particles in homogeneous, constant and/or
oscillating magnetic fields in the non-relativistic approximation. A special
role of the geometric center of the particle trajectory is elucidated. In
quantum case it becomes a 'fuzzy point' with non-commuting coordinates, an
element of non-commutative geometry which enters into the traditional control
problems. We show that its application extends beyond the usually considered
time independent magnetic fields of the quantum Hall effect. Some simple cases
of magnetic control by oscillating fields lead to the stability maps differing
from the traditional Strutt diagram.Comment: 28 pages, 8 figure
The Astrophysical Multipurpose Software Environment
We present the open source Astrophysical Multi-purpose Software Environment
(AMUSE, www.amusecode.org), a component library for performing astrophysical
simulations involving different physical domains and scales. It couples
existing codes within a Python framework based on a communication layer using
MPI. The interfaces are standardized for each domain and their implementation
based on MPI guarantees that the whole framework is well-suited for distributed
computation. It includes facilities for unit handling and data storage.
Currently it includes codes for gravitational dynamics, stellar evolution,
hydrodynamics and radiative transfer. Within each domain the interfaces to the
codes are as similar as possible. We describe the design and implementation of
AMUSE, as well as the main components and community codes currently supported
and we discuss the code interactions facilitated by the framework.
Additionally, we demonstrate how AMUSE can be used to resolve complex
astrophysical problems by presenting example applications.Comment: 23 pages, 25 figures, accepted for A&
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