Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Inner Structure of LambdaCDM Halos I: A Numerical Convergence Study   We present a comprehensive set of convergence tests which explore the role of
various numerical parameters on the equilibrium structure of a simulated dark
matter halo. We report results obtained with two independent, state-of-the-art,
multi-stepping, parallel N-body codes: PKDGRAV and GADGET. We find that
convergent mass profiles can be obtained for suitable choices of the
gravitational softening, timestep, force accuracy, initial redshift, and
particle number. For softenings chosen so that particle discreteness effects
are negligible, convergence in the circular velocity is obtained at radii where
the following conditions are satisfied: (i) the timestep is much shorter than
the local orbital timescale; (ii) accelerations do not exceed a characteristic
acceleration imprinted by the gravitational softening; and (iii) enough
particles are enclosed so that the collisional relaxation timescale is longer
than the age of the universe. The most stringent requirement for convergence is
typically that imposed on the particle number by the collisional relaxation
criterion, which implies that in order to estimate accurate circular velocities
at radii where the density contrast may reach $\sim 10^6$, the region must
enclose of order 3000 particles (or more than a few times $10^6$ within the
virial radius). Applying these criteria to a galaxy-sized $\Lambda$CDM halo, we
find that the spherically-averaged density profile becomes progressively
shallower from the virial radius inwards, reaching a logarithmic slope
shallower than -1.2 at the innermost resolved point, $r \sim 0.005 r_{200}$,
with little evidence for convergence to a power-law behaviour in the inner
regions.

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The categories of this paper are: atom-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: math
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The categories of this paper are: cs
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The categories of this paper are: gr-qc
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The categories of this paper are: stat
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The categories of this paper are: physics
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The categories of this paper are: alg-geom
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The categories of this paper are: cond-mat
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The categories of this paper are: q-bio
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The categories of this paper are: hep-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: math-ph
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The categories of this paper are: nlin
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The categories of this paper are: cmp-lg