Hi, here is my problem :

Let H be a Hilbert space with basis {u_k}_k>0.

Verify that the operator T defined by :

T(u_k) = 1/k . u_k+1

is compact but has no eigenvectors.

To show it is compact, I tried to use the definition : T is compact if any bounded sequence {f_k} in H has a subsequence {f_nk}_k>0 such that {T(f_nk)} converges.

I took a bounded sequence {f_k} in H and approximated the f_k's by linear combinations of the basis elements {u_k}. But I don't see where this is supposed to lead me.

For the eigenvectors, I am lost.

Any ideas ?

Thanks.