Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: C^2-Ray: A new method for photon-conserving transport of ionizing
  radiation   We present a new numerical method for calculating the transfer of ionizing
radiation, called C^2-Ray=Conservative, Causal Ray-tracing method. The method
is explicitly photon-conserving, so the depletion of ionizing photons by
bound-free opacity is guaranteed to equal the photoionizations these photons
caused. As a result, grid cells can be large and very optically-thick without
loss of accuracy. The method also uses an analytical relaxation solution for
the ionization rate equations for each time step which can accommodate time
steps which greatly exceed the characteristic ionization and ionization front
crossing times. Together, these features make it possible to integrate the
equation of transfer along a ray with many fewer cells and time steps than
previous methods. For multi-dimensional calculations, the code utilizes
short-characteristics ray tracing. C^2-Ray is well-suited for coupling
radiative transfer to gas and N-body dynamics methods, on both fixed and
adaptive grids, without imposing additional limitations on the time step and
grid spacing. We present several tests of the code involving propagation of
ionization fronts in one and three dimensions, in both homogeneous and
inhomogeneous density fields. We compare to analytical solutions for the
ionization front position and velocity, some of which we derive here for the
first time.

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The categories of this paper are: mtrl-th
10
The categories of this paper are: q-bio
3
The categories of this paper are: physics
13
The categories of this paper are: quant-ph
25
The categories of this paper are: patt-sol
27
The categories of this paper are: comp-gas
21
The categories of this paper are: adap-org
5
The categories of this paper are: gr-qc
15
The categories of this paper are: nucl-ex
8
The categories of this paper are: hep-ex
12
The categories of this paper are: nucl-th
1
The categories of this paper are: cs
11
The categories of this paper are: hep-lat
24
The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom