Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Necessary Condition for Individual Time-Steps in SPH Simulations   We show that the smoothed particle hydrodynamics (SPH) method, used with
individual time-steps in the way described in the literature, cannot handle
strong explosion problems correctly. In the individual time-step scheme,
particles determine their time-steps essentially from a local Courant
condition. Thus they cannot respond to a strong shock, if the pre-shock
timescale is too long compared to the shock timescale. This problem is not
severe in SPH simulations of galaxy formation with a temperature cutoff in the
cooling function at $10^4 {\rm K}$, while it is very dangerous for simulations
in which the multiphase nature of the interstellar medium under $10^4 {\rm K}$
is taken into account. A solution for this problem is to introduce a time-step
limiter which reduces the time-step of a particle if it is too long compared to
the time-steps of its neighbor particles. Thus this kind of time-step
constraint is essential for the correct treatment of explosions in
high-resolution SPH simulations with individual time-steps.

13
The categories of this paper are: quant-ph
2
The categories of this paper are: math
5
The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom
7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th
30
The categories of this paper are: q-alg
14
The categories of this paper are: math-ph
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
11
The categories of this paper are: hep-lat
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
0
The categories of this paper are: hep-ph