Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Primordial-black-hole mergers in dark-matter spikes   It has been suggested that primordial black holes (PBHs) of roughly 30 solar
masses could make up the dark matter and if so, might account for the recent
detections by LIGO involving binary black holes in this mass range. It has also
been argued that the super-massive black holes (SMBHs) that reside at galactic
centers may be surrounded by extremely-dense dark-matter (DM) spikes. Here we
show that the rate for PBH mergers in these spikes may well exceed the merger
rate considered before in galactic dark-matter halos, depending on the
magnitudes of two competing effects on the DM spikes: depletion of PBHs due to
relaxation and replenishment due to PBHs in loss cone. This may provide a
plausible explanation for the current rate of detection of mergers of
30-solar-mass black holes, even if PBHs make up a subdominant contribution to
the dark matter. The gravitational-wave signals from such events will always
originate in galactic centers, as opposed to those from halos, which are
expected to have little correlation with luminous-galaxy positions.

34
The categories of this paper are: chem-ph
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
5
The categories of this paper are: gr-qc
2
The categories of this paper are: math
21
The categories of this paper are: adap-org
17
The categories of this paper are: q-fin
36
The categories of this paper are: cmp-lg
10
The categories of this paper are: q-bio
26
The categories of this paper are: bayes-an
24
The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
1
The categories of this paper are: cs
18
The categories of this paper are: econ
7
The categories of this paper are: hep-th