Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I know that if $V$ is a vector space over a field $k,$ then

  1. $\operatorname{End}(V)$ has no non-trivial ideals if $\dim V<\infty;$
  2. $\operatorname{End}(V)$ has exactly one non-trivial ideal if $\dim V=\aleph_0.$

Do we know how many ideals $\operatorname{End}(V)$ can have when $\dim V>\aleph_0?$ Can we describe them?

share|cite|improve this question
up vote 5 down vote accepted

If $\text{dim}(V)$ is infinite, then for each infinite cardinal $\kappa\leq\text{dim}(V)$ we have the ideal of endomorphisms whose ranges have dimension $<\kappa$.

share|cite|improve this answer
Are those the only ones? – KotelKanim Feb 16 '12 at 13:45
Yes: if $I$ is an ideal and contains an endomorphism whose range is dimension $\lambda$, then it contains all endomorphisms with range of dimension $\lambda$ (just compose with an appropriate isomorphism between the ranges). – Arturo Magidin Feb 16 '12 at 16:58

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.