Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: New thresholds for Primordial Black Hole formation during the QCD phase
  transition   Primordial Black Holes (PBHs) might have formed in the early Universe as a
consequence of the collapse of density fluctuations with an amplitude above a
critical value $\delta_{c}$: the formation threshold. Although for a
radiation-dominated Universe $\delta_{c}$ remains constant, if the Universe
experiences some dust-like phases (e.g. phase transitions) $\delta_{c}$ might
decrease, improving the chances of PBH formation. We studied the evolution of
$\delta_{c}$ during the QCD phase transition epoch within three different
models: Bag Model (BM), Lattice Fit Model (LFM), and Crossover Model (CM). We
found that the reduction on the background value of $\delta_{c}$ can be as high
as $77\%$ (BM), which might imply a $\sim10^{-10}$ probability of PBHs forming
at the QCD epoch.

15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
11
The categories of this paper are: hep-lat
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th
29
The categories of this paper are: funct-an