What is meant by a particle should not overclose the univese? what is overclose?

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The term "overclose" refers to a particle's energy density exceeding the limits set by cosmological observations, which could lead to an excessively dense universe. In the context of axions, their mass must fall within a specific range to prevent this overclosure. The lower bound is determined by the need for axions to avoid contributing too much energy density, while the upper bound is established through accelerator searches and stellar evolution studies. This balance ensures that axions do not disrupt the universe's structure and expansion. Understanding these constraints is crucial for theoretical physics and cosmology.
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what is meant by a particle should not overclose the univese? what is overclose? is it packed?


''The allowed axion mass range, bounded from below by the requirement
that axions should not overclose the universe and from above by accelerator searches
and stellar evolution.
 
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Welcome melezmelez,

I'd interpret it as having more energy density than allowed by cosmological observations.
 

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