# Does there exist a star-Lindelöf space which is not star-$L$-Lindelöf?

1. A space $$X$$ is said to be star-Lindelöf if for every open cover $$\mathcal U$$ of $$X$$ there exists a countable subset $$\mathcal V\subseteq\mathcal U$$ such that $$St(\cup\mathcal V,\mathcal U)=X$$.

2. A space $$X$$ is said to be star-$$L$$-Lindelöf if for every open cover $$\mathcal U$$ of $$X$$ there exists a Lindelöf subset $$Y$$ of $$X$$ such that $$St(Y,\mathcal U)=X$$.

It is clear from the above definitions that every star-$$L$$-Lindelöf space is star-Lindelöf. But we don't know if there eixsts a star-Lindelöf space which is not star-$$L$$-Lindelöf.

• @HennoBrandsma: Sorry for the typographical errors. You are right. Every Lindelöf space is star-$L$-Lindelöf. Actually we need a star-Lindelöf space which is not star-$L$-Lindelöf. Feb 1 at 13:43

The question you ask has already been answered by Song with different terminology in the following paper (see Example 2.3):

ON L-STARCOMPACT SPACES, Czechoslovak Mathematical Journal, 56 (131) (2006), 781–788

https://cmj.math.cas.cz/full/56/2/cmj56_2_40.pdf

In addition, you may also consider and check some properties of the star-P type in the following sense (defined in "Classes defined by stars and neighbourhood assignments" by van Mill et.al.):

Let P be a topological property. We said that a spaces X is star-P if for any open cover U of X, there exists a subspace Y of X with property P such that St(Y,U)=X.

Thus, what you call star-L-Lindelof is the same as star-Lindelof with above definition.