# Explicit Hamel basis for an infinite dimensional Banach space

Does there exist an explicit example of an algebraic basis in a Banach space with infinite dimension? By "explicit", I mean a basis that can be constructed without using the axiom of choice for chosing the basis elements.

I know that such a basis must be uncountable and that for some Banach spaces it can be shown that there is no such "explicit" basis.

• I suspect no such example is known. Indeed, I suspect there is no example (established in ZF) of an infinite-dimensional Banach space that has a Hamel basis. – GEdgar Jan 10 '18 at 12:50
• @GEdgar This really blows my mind. This just means that if we have any explicit uncountable set (like $\mathbb{R}$) and take the free vector space $F$ over this set, then we can't ever define a norm on $F$ such that $F$ is complete w.r.t this norm. – Andrei Kh Mar 13 '18 at 23:26