In the theorem 3.6 of Juhász's Cardinal Functions in General Topology appears the following symbol about sequence: $\frown$
The role context of it's appearance is the following:
Theorem. Let X be an compact topological space and $\kappa$ an cardinal such that $\chi(p,X)\geq \kappa$, for all $p\in X$. Then $|X|\geq 2^\kappa$.
Proof. First, set $\kappa =\omega$; we shall prove a little more than stated, namely that $X$ can be mapped continuously onto the interval $[0,1]$. To achieve this, we first define be induction on $n\in\omega$ an non-empty open subset $U_{\varepsilon}$ of $X$ for each finite sequence $\varepsilon\in 2^n$ in such way that
- $\overline{U_{\overset{\frown}{\varepsilon 0}}} \cup \overline{U_{\overset{\frown}{\varepsilon 1}}} \subseteq U_{\varepsilon}$
- $\overline{U_{\overset{\frown}{\varepsilon 0}}} \cap \overline{U_{\overset{\frown}{\varepsilon 1}}} = \emptyset$
The proof goes on...
What is the name of this symbol and what does it means?