{ "id": "1507.03241", "version": "v1", "published": "2015-07-12T15:28:20.000Z", "updated": "2015-07-12T15:28:20.000Z", "title": "Closed ideals in $\\mathcal{L}(X)$ and $\\mathcal{L}(X^*)$ when $X$ contains certain copies of $\\ell_p$ and $c_0$", "authors": [ "Ben Wallis" ], "comment": "28 pages", "categories": [ "math.FA" ], "abstract": "Suppose $X$ is a real or complexified Banach space containing a complemented copy of $\\ell_p$, $p\\in(1,2)$, and a copy (not necessarily complemented) of either $\\ell_q$, $q\\in(p,\\infty)$, or $c_0$. Then $\\mathcal{L}(X)$ and $\\mathcal{L}(X^*)$ each admit continuum many closed ideals. If in addition $q\\geq p'$, $\\frac{1}{p}+\\frac{1}{p'}=1$, then the closed ideals of $\\mathcal{L}(X)$ and $\\mathcal{L}(X^*)$ each fail to be linearly ordered. We obtain additional results in the special cases of $\\mathcal{L}(\\ell_1\\oplus\\ell_q)$ and $\\mathcal{L}(\\ell_p\\oplus c_0)$, $1