Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Effect of Radiative Feedbacks for Resonant Transitions during
  Cosmological Recombination   The inhibition of the total HI $n\leftrightarrow 1$ transition rate by
delayed resonant reabsorption of HI $(n+1)\to 1$ photons by HI $n\to 1$ line
which is possible due to cosmological redshift is considered semi-analytically.
The method taking into account this effect in the frame of simple three-level
approximation model of recombination is suggested. It is confirmed that the
resonant feedbacks affect ionization fraction at the level about 0.2% for the
epoch of last scattering.
  Similar consideration of HeI $2^1P\leftrightarrow 1^1S$ $\Rightarrow$ HeI
$2^3P\leftrightarrow 1^1S$ feedback for helium is provided. It is confirmed
that allowance of this feedback leads to increase of predicted free electron
fraction by 0.12% at $z\simeq 2300$. It is shown that taking into account
absorption and thermalization of HeI $2^1P\leftrightarrow 1^1S$ resonant
superequilibrium photons (during their redshifting to the HeI
$2^3P\leftrightarrow 1^1S$ frequency) by small amount of neutral hydrogen
($10^{\rm -7} - 10^{\rm -4}$ of total number of hydrogen atoms and ions)
existing in helium recombination epoch is important for correct consideration
of this helium feedback.

28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
4
The categories of this paper are: cond-mat
9
The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
34
The categories of this paper are: chem-ph
3
The categories of this paper are: physics
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
27
The categories of this paper are: comp-gas
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg