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Feb 17, 2010 at 9:17 comment added Yemon Choi It's up to you, really. The original question doesn't have to be perfect and complete.
Feb 17, 2010 at 9:07 comment added Yemon Choi As regards editing the original question: I think you should be able to edit it yourself. Personally I would prefer that you delete as little as possible, and instead add a new part; that way one can see what the original answers of Bill Johnson and myself are referring to.
Feb 17, 2010 at 9:03 comment added Yemon Choi Does my updated version answer your question? In the case you refer to, the ratio of the weights does not lie in $c_0$, and so you are right that the estimates don't work: indeed, this case, the embedding is NOT compact.
Feb 17, 2010 at 8:46 comment added Leandro I get stuck about the last remark of your answer. Suppose that $\Omega_p$ now, is given as above but the weights are replaced by a sequence $p(i)\in C_0(\mathbb{Z}^d)$ and for $\Omega_{p'}$, the weights are replaced by $p'(i)\in C_0(\mathbb{Z}^d)$. If $p'(i)\leq p(i)$ then the embedding $\Omega_p\hookrightarrow \Omega_{p'}$ is well defined. Let's suppose also the the sequence decay monotonically, however if $$0<\liminf_{i\in\mathbb{Z}^d} \frac{|p(i)|}{|p'(i)|}$$ Your norm estimates does not works anymore. even in this case the Bill's argument is in hold ? Thanks again
Feb 17, 2010 at 8:41 history edited Yemon Choi CC BY-SA 2.5
clarified last para in response to question in comments
Feb 17, 2010 at 8:37 comment added Yemon Choi I wasn't very clear in my last paragraph: I'll edit it now. Bill is talking about transforming your original question so that instead of looking at a simple operator (inclusion) between two complicated-seeming spaces, one looks at a slightly (but not very) complicated operator on a simple space, namely l^R.
Feb 16, 2010 at 5:53 vote accept Leandro
Feb 16, 2010 at 5:04 comment added Leandro Yemon tahnk you very much for the answer, I read Bill's answer also but with my background in functional analysis I took some time to figure out what is happening, but after read your argument everything it was clear for me. Thanks again !!
Feb 16, 2010 at 4:58 vote accept Leandro
Feb 16, 2010 at 4:58
Feb 16, 2010 at 2:13 history answered Yemon Choi CC BY-SA 2.5