Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Limits on primordial black holes from $\mu$ distortions in cosmic
  microwave background   If primordial black holes (PBHs) form directly from inhomogeneities in the
early Universe, then the number in the mass range $10^5 -10^{12}M_{\odot}$ is
severely constrained by upper limits to the $\mu$ distortion in the cosmic
microwave background (CMB). This is because inhomogeneities on these scales
will be dissipated by Silk damping in the redshift interval $5\times
10^4\lesssim z\lesssim2\times 10^6$. If the primordial fluctuations on a given
mass scale have a Gaussian distribution and PBHs form on the high-$\sigma$
tail, as in the simplest scenarios, then the $\mu$ constraints exclude PBHs in
this mass range from playing any interesting cosmological role. Only if the
fluctuations are highly non-Gaussian, or form through some mechanism unrelated
to the primordial fluctuations, can this conclusion be obviated.

4
The categories of this paper are: cond-mat
23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
0
The categories of this paper are: hep-ph
22
The categories of this paper are: chao-dyn
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
30
The categories of this paper are: q-alg
11
The categories of this paper are: hep-lat
7
The categories of this paper are: hep-th
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
32
The categories of this paper are: atom-ph