We prove, in a general framework, the existence of a closed infinite-dimensional subspace consisting of universal series.
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-sm198-2-2, author = {St\'ephane Charpentier}, title = {On the closed subspaces of universal series in Banach spaces and Fr\'echet spaces}, journal = {Studia Mathematica}, volume = {196}, year = {2010}, pages = {121-145}, zbl = {1201.30005}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-sm198-2-2} }
Stéphane Charpentier. On the closed subspaces of universal series in Banach spaces and Fréchet spaces. Studia Mathematica, Tome 196 (2010) pp. 121-145. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-sm198-2-2/