Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Anisotropies of the Cosmic Background Radiation in a Reionized Universe   We trace the evolution of cosmic microwave background photons propagating
through a reionized model universe. The reionization of the intergalactic
medium is achieved by UV photons emitted from the decaying `hot' dark matter
neutrinos. The model universe is represented by a comoving cube through which
we propagate photons and subject them to the Sachs-Wolfe effect and Thomson
scattering off the ionized fraction of the IGM, beginning at z=1900 until the
present z=0. The simulation follows the evolving matter inhomogeneities and
microwave background photons into the present nonlinear regime and yields
temperature maps of the microwave sky as a comoving observer would detect. Our
temperature maps display anisotropies on scales ranging from 2 to 8 degrees
with rms amplitudes ranging from DT/T_{rms} =2.8 to 3.4 times 10^{-5} without
reionization. If we allow the neutrinos to decay and subsequently reionize the
IGM, the level of the temperature anisotropies is reduced to DT/T=0.8 to 1.1
times 10^{-5}. This includes the Doppler shifts suffered by the CMB photons as
they scatter off the moving ionized fraction of the IGM. If, however,
reionization is caused by a late and sudden energy input into the IGM, we find
that some reduction in $\Delta T/T$ occurs, but not enough to make this
scenario consistent with observations. We find that the decaying neutrino
hypothesis is more efficient at reducing primordial anisotropies and generates
smaller Doppler anisotropies than a model reionized via a late and sudden
energy input into the IGM.

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The categories of this paper are: cond-mat
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The categories of this paper are: hep-ex
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The categories of this paper are: gr-qc
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The categories of this paper are: math-ph
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The categories of this paper are: solv-int
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The categories of this paper are: ao-sci
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The categories of this paper are: alg-geom
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The categories of this paper are: cmp-lg
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The categories of this paper are: eess
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The categories of this paper are: quant-ph
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The categories of this paper are: physics
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The categories of this paper are: mtrl-th
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The categories of this paper are: cs
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The categories of this paper are: acc-phys
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The categories of this paper are: nlin
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The categories of this paper are: chao-dyn