Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Constraints on the cosmic string loop collapse fraction from Primordial
  Black Holes   A small fraction, $f$, of cosmic string loops can collapse to form Primordial
Black Holes (PBHs). Constraints on the abundance of PBHs can therefore be used
to constrain $f$. We update these calculations, taking into account the PBH
extended mass function, and find $f < 10^{-31} (G \mu/ c^2)^{-3/2}$. This is
roughly two orders of magnitude tighter than previous constraints. The
improvement from the tighter constraints on the abundance of PBHs is partly
off-set by refinements to the theoretical calculation of the cosmic string loop
formation rate.

10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex
33
The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
3
The categories of this paper are: physics
28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin
1
The categories of this paper are: cs
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
19
The categories of this paper are: eess
2
The categories of this paper are: math