ars.</p></li>
</ul>
</section>
<section id="Conclusion">
<h2>Conclusion<a class="headerlink" href="#Conclusion" title="Link to this heading"></a></h2>
<ul class="simple">
<li><p>The merger rate density of binary black hole (BBH) mergers from Population III (Pop. III) stars, primordial black holes (PBHs), and Population I/II (Pop. I/II) stars is a topic of active research. All three models suggest that BBH mergers are a common occurrence in the universe, but there is still a significant range of uncertain